New Antidepressant - Old Tricks

The past decade has been a bad one for antidepressant manufacturers.

Quite apart from all the bad press these drugs have been getting lately, there's been a remarkable lack of new antidepressants making it to the market. The only really novel drugs to hit the shelves since 2000 have been agomelatine and vilazodone. There were a couple of others that were just minor variants on old molecules, but that's it. Quite a contrast from the 1990s when new drugs were ten-a-penny.

This makes "Lu AA21004" rather special. It's a new antidepressant currently in development and by all accounts it's making good progress. It's now in Phase III trials, the last stage before approval. And a large clinical trial has just been published finding that it works.

But is it a medical advance or merely a commercial one?

Pharmacologically, Lu AA21004 is kind of a new twist on an old classic . Its main mechanism of action is inhibiting the reuptake of serotonin, just like Prozac and other SSRIs. However, unlike them, it also blocks serotonin 5HT3 and 5HT7 receptors, activates 5HT1A receptors and partially agonizes 5HT1B.

None of these things cry out "antidepressant" to me, but they do at least make it a bit different.

The new trial took 430 depressed people and randomized them to get Lu AA21004, at two different doses, 5mg or 10mg, or the older antidepressant venlafaxine at the high-ish dose of 225 mg, or placebo.

It worked. Over 6 weeks, people on the new drug improved more than those on placebo, and equally as well as people on venlafaxine; the lower 5 mg dose was a bit less effective, but not significantly so.

The size of the effect was medium, with a benefit over-and-above placebo of about 5 points on the MADRS depression scale, which considering that the baseline scores in this study averaged 34, is not huge, but it compares well to other antidepressant trials.

Now we come to the side effects, and this is the most important bit, as we'll see later. The authors did not specifically probe for these, they just relied on spontaneous report, which tends to underestimate adverse events.


Basically, the main problem with Lu AA21004 was that it made people sick. Literally - 9% of people on the highest dose suffered vomiting, and 38% got nausea. However, the 5 mg dose was no worse than venlafaxine for nausea, and was relatively vomit-free. Unlike venlafaxine, it didn't cause dry mouth, constipation, or sexual problems.

So that's lovely then. Let's get this stuff to market!

Hang on.

The big selling point for this drug is clearly the lack of side effects. It was no more effective than the (much cheaper, because off-patent) venlafaxine. It was better tolerated, but that's not a great achievement to be honest. Venlafaxine is quite notorious for causing side effects, especially at higher doses.

I take venlafaxine 300 mg and the side effects aren't the end of the world, but they're no fun, and the point is, they're well known to be worse than you get with other modern drugs, most notably SSRIs.

If you ask me, this study should have compared the new drug to an SSRI, because they're used much more widely than venlafaxine. Which one? How about escitalopram, a drug which is, according to most of the literature, one of the best SSRIs, as effective as venlafaxine, but with fewer side effects.

Actually, according to Lundbeck, who make escitalopram, it's even better than venlafaxine. Now, they would say that, given that they make it - but the makers of Lu AA21004 ought to believe them, because, er, they're the same people. "Lu" stands for Lundbeck.

The real competitor for this drug, according to Lundbeck, is escitalopram. But no-one wants to be in competition with themselves.

This may be why, although there are no fewer than 26 registered clinical trials of Lu AA21004 either ongoing or completed, only one is comparing it to an SSRI. The others either compare it to venlafaxine, or to duloxetine, which has even worse side effects. The one trial that will compare it to escitalopram has a narrow focus (sexual dysfunction).

Pharmacologically, remember, this drug is an SSRI with a few "special moves", in terms of hitting some serotonin receptors. The question is - do those extra tricks actually make it better? Or is it just a glorified, and expensive, new SSRI? We don't know and we're not going to find out any time soon.

If Lu AA21004 is no more effective, and no better tolerated, than tried-and-tested old escitalopram, anyone who buys it will be paying extra for no real benefit. The only winner, in that case, being Lundbeck - especially given that escitalopram goes off-patent in 2012...

Alvarez E, Perez V, Dragheim M, Loft H, & Artigas F (2011). A double-blind, randomized, placebo-controlled, active reference study of Lu AA21004 in patients with major depressive disorder. The International Journal of Neuropsychopharmacology , 1-12 PMID: 21767441

New Antidepressant - Old Tricks

The past decade has been a bad one for antidepressant manufacturers.

Quite apart from all the bad press these drugs have been getting lately, there's been a remarkable lack of new antidepressants making it to the market. The only really novel drugs to hit the shelves since 2000 have been agomelatine and vilazodone. There were a couple of others that were just minor variants on old molecules, but that's it. Quite a contrast from the 1990s when new drugs were ten-a-penny.

This makes "Lu AA21004" rather special. It's a new antidepressant currently in development and by all accounts it's making good progress. It's now in Phase III trials, the last stage before approval. And a large clinical trial has just been published finding that it works.

But is it a medical advance or merely a commercial one?

Pharmacologically, Lu AA21004 is kind of a new twist on an old classic . Its main mechanism of action is inhibiting the reuptake of serotonin, just like Prozac and other SSRIs. However, unlike them, it also blocks serotonin 5HT3 and 5HT7 receptors, activates 5HT1A receptors and partially agonizes 5HT1B.

None of these things cry out "antidepressant" to me, but they do at least make it a bit different.

The new trial took 430 depressed people and randomized them to get Lu AA21004, at two different doses, 5mg or 10mg, or the older antidepressant venlafaxine at the high-ish dose of 225 mg, or placebo.

It worked. Over 6 weeks, people on the new drug improved more than those on placebo, and equally as well as people on venlafaxine; the lower 5 mg dose was a bit less effective, but not significantly so.

The size of the effect was medium, with a benefit over-and-above placebo of about 5 points on the MADRS depression scale, which considering that the baseline scores in this study averaged 34, is not huge, but it compares well to other antidepressant trials.

Now we come to the side effects, and this is the most important bit, as we'll see later. The authors did not specifically probe for these, they just relied on spontaneous report, which tends to underestimate adverse events.


Basically, the main problem with Lu AA21004 was that it made people sick. Literally - 9% of people on the highest dose suffered vomiting, and 38% got nausea. However, the 5 mg dose was no worse than venlafaxine for nausea, and was relatively vomit-free. Unlike venlafaxine, it didn't cause dry mouth, constipation, or sexual problems.

So that's lovely then. Let's get this stuff to market!

Hang on.

The big selling point for this drug is clearly the lack of side effects. It was no more effective than the (much cheaper, because off-patent) venlafaxine. It was better tolerated, but that's not a great achievement to be honest. Venlafaxine is quite notorious for causing side effects, especially at higher doses.

I take venlafaxine 300 mg and the side effects aren't the end of the world, but they're no fun, and the point is, they're well known to be worse than you get with other modern drugs, most notably SSRIs.

If you ask me, this study should have compared the new drug to an SSRI, because they're used much more widely than venlafaxine. Which one? How about escitalopram, a drug which is, according to most of the literature, one of the best SSRIs, as effective as venlafaxine, but with fewer side effects.

Actually, according to Lundbeck, who make escitalopram, it's even better than venlafaxine. Now, they would say that, given that they make it - but the makers of Lu AA21004 ought to believe them, because, er, they're the same people. "Lu" stands for Lundbeck.

The real competitor for this drug, according to Lundbeck, is escitalopram. But no-one wants to be in competition with themselves.

This may be why, although there are no fewer than 26 registered clinical trials of Lu AA21004 either ongoing or completed, only one is comparing it to an SSRI. The others either compare it to venlafaxine, or to duloxetine, which has even worse side effects. The one trial that will compare it to escitalopram has a narrow focus (sexual dysfunction).

Pharmacologically, remember, this drug is an SSRI with a few "special moves", in terms of hitting some serotonin receptors. The question is - do those extra tricks actually make it better? Or is it just a glorified, and expensive, new SSRI? We don't know and we're not going to find out any time soon.

If Lu AA21004 is no more effective, and no better tolerated, than tried-and-tested old escitalopram, anyone who buys it will be paying extra for no real benefit. The only winner, in that case, being Lundbeck - especially given that escitalopram goes off-patent in 2012...

Alvarez E, Perez V, Dragheim M, Loft H, & Artigas F (2011). A double-blind, randomized, placebo-controlled, active reference study of Lu AA21004 in patients with major depressive disorder. The International Journal of Neuropsychopharmacology , 1-12 PMID: 21767441

Revenge Of The Depression Gene

Last year, the world of psychiatric genetics was rocked by the news that a highly-studied gene, believed to be associated with depression, wasn't in fact linked to depression at all.

The genetic variant was 5-HTTLPR. It's a length variant in the gene coding for the serotonin transporter protein (5HTT) which the target of antidepressants like Prozac. There are two flavors of this variant, short and long.

Many studies have shown that the short ("s") variant is associated with a high risk of getting depression in response to stress - but then last year a large meta-analysis of all the evidence concluded that there was in reality no link. Bummer.

Now another team of researchers have done a new analysis of the 5-HTTLPR & stress & depression data and they claim that there is a link after all: hooray! So who's right? I'm not sure, but the new paper raises many questions.

The new paper puts together the results of all 54 studies which have looked at this gene in the context of depression, caused by any kind of stress. The authors were intentionally liberal in their inclusion criteria: studies in any population were OK, for example they included people with Parkinson's disease or heart disease.

They say that this is the main difference between the present work and earlier meta-analyses that found no link. The famous 2010 paper, for example, only included 14 studies because they only considered certain kinds of stress.

Anyway, the short variant is associated with depression after all, across all of the studies. They extracted the p values from the results of all previous studies, and took the average of those, weighted by the sample size. They found a very significant association: P=.00002.

Here's all the results. Each square is a study, the further to the left, the more strongly they found an association. Bigger squares mean larger studies. As you can see, most studies found a link but the three largest studies - which were much larger than the others - found none. Hmm.

In terms of specific kinds of stress, they found strong evidence that "specific stressors" (like medical illness), and childhood trauma, were associated with more depression in s-allele carriers. However, in the studies on "Stressful Life Events", which is a broad category meaning pretty much anything bad that happens, the evidence was weaker. The previous meta-analyses only considered these studies.

Ultimately, I think this analysis should remind us that the issue of 5HTTLPR is still "open", but I have concerns about the dataset. The fact that larger studies seem less likely to be positive is a classic warning sign of publication bias.

The authors do consider this and say that they calculate that there would have to be over 700 unpublished, negative studies out there, in order to make the overall data negative. They also find that you could ignore the smallest 45 studies and still find a result. But still. Something doesn't feel right. Maybe I just have the wrong 5HTTLPR variant.

Karg K, Burmeister M, Shedden K, & Sen S (2011). The Serotonin Transporter Promoter Variant (5-HTTLPR), Stress, and Depression Meta-analysis Revisited: Evidence of Genetic Moderation. Archives of general psychiatry, 68 (5), 444-54 PMID: 21199959

Revenge Of The Depression Gene

Last year, the world of psychiatric genetics was rocked by the news that a highly-studied gene, believed to be associated with depression, wasn't in fact linked to depression at all.

The genetic variant was 5-HTTLPR. It's a length variant in the gene coding for the serotonin transporter protein (5HTT) which the target of antidepressants like Prozac. There are two flavors of this variant, short and long.

Many studies have shown that the short ("s") variant is associated with a high risk of getting depression in response to stress - but then last year a large meta-analysis of all the evidence concluded that there was in reality no link. Bummer.

Now another team of researchers have done a new analysis of the 5-HTTLPR & stress & depression data and they claim that there is a link after all: hooray! So who's right? I'm not sure, but the new paper raises many questions.

The new paper puts together the results of all 54 studies which have looked at this gene in the context of depression, caused by any kind of stress. The authors were intentionally liberal in their inclusion criteria: studies in any population were OK, for example they included people with Parkinson's disease or heart disease.

They say that this is the main difference between the present work and earlier meta-analyses that found no link. The famous 2010 paper, for example, only included 14 studies because they only considered certain kinds of stress.

Anyway, the short variant is associated with depression after all, across all of the studies. They extracted the p values from the results of all previous studies, and took the average of those, weighted by the sample size. They found a very significant association: P=.00002.

Here's all the results. Each square is a study, the further to the left, the more strongly they found an association. Bigger squares mean larger studies. As you can see, most studies found a link but the three largest studies - which were much larger than the others - found none. Hmm.

In terms of specific kinds of stress, they found strong evidence that "specific stressors" (like medical illness), and childhood trauma, were associated with more depression in s-allele carriers. However, in the studies on "Stressful Life Events", which is a broad category meaning pretty much anything bad that happens, the evidence was weaker. The previous meta-analyses only considered these studies.

Ultimately, I think this analysis should remind us that the issue of 5HTTLPR is still "open", but I have concerns about the dataset. The fact that larger studies seem less likely to be positive is a classic warning sign of publication bias.

The authors do consider this and say that they calculate that there would have to be over 700 unpublished, negative studies out there, in order to make the overall data negative. They also find that you could ignore the smallest 45 studies and still find a result. But still. Something doesn't feel right. Maybe I just have the wrong 5HTTLPR variant.

Karg K, Burmeister M, Shedden K, & Sen S (2011). The Serotonin Transporter Promoter Variant (5-HTTLPR), Stress, and Depression Meta-analysis Revisited: Evidence of Genetic Moderation. Archives of general psychiatry, 68 (5), 444-54 PMID: 21199959

Blue Morning

Recently, I wrote about diurnal mood variation: the way in which depression often waxes and wanes over the course of the day. Mornings are generally the worst.

A related phenomenon is late insomnia, or "early morning waking".

But this phrase is rather an understatement. Everyone's woken up early. Maybe you had a flight to catch. Or you were drunk and threw up. Or you just needed a pee. That's early morning waking, but not the depressive kind. When you're depressed, the waking up is the least of your problems.

Suddenly, you are awake, more awake than you've ever been. And you know something terrible has happened, or is about to happen, or that you've done something terribly wrong. It feels like a Eureka moment. You can be a level-headed person, not given to jumping to conclusions, but you will be convinced of this.

In a panic attack, you think you're going to die. Your heart is beating too fast, your breathing's too deep: your body is exploding, you can feel it too closely. With this, With this, you think you should die or even, in some sense, already have. It feels cold: you can no longer feel the warmth of your own body.

The moment passes; the terrible truth that you were so certain of five minutes ago becomes a little doubtful. Maybe it's not quite so bad. At this point, the wakefulness goes too, and you become, well, as tired as you ought to be at 3 am. You try to go back to sleep. If you're lucky, you succeed. If not, you lie awake until morning in a state of miserable contemplation.

While it's happening, you think that you're going to feel this way forever; bizarrely, you think you always have felt this way. In fact, this is the darkest hour.

*

Why does this happen? There has been almost no research on early morning waking. Presumably, because it's so hard to study. To observe it, you would have to get your depressed patients to spend all night in your brain scanner (or, if you prefer, on your analyst's couch), and even then, it doesn't happen every night.

But here's my theory: the key is the biology of sleep. There are many stages of sleep; at a very rough approximation there's dreaming REM, and dreamless slow-wave. Now, REM sleep tends to happen during the second half of the night - the early morning.

During REM sleep, the brain is, in many respects, awake. This is presumably what allows us to have concious dreams. Whereas in slow wave sleep, the brain really is offline; slow waves are also seen in the brain of people in comas, or under deep anaesthesia.

When we're awake, the brain is awash with modulatory neurotransmitters, such as serotonin, norepinephrine, and acetylcholine. During REM, acetylcholine is present, while in slow-wave sleep it's not; indeed acetylcholine may well be what stops slow waves and "wakes up" the cortex.

But unlike during waking, serotonin and norepinephrine neurons are entirely inactive during REM sleep - and only during REM sleep. This fact is surprisingly little-known, but it seems to me that it explains an awful lot.

For one thing, it explains why drugs which increase serotonin levels, such as SSRI antidepressants, inhibit REM sleep. Indeed, high doses of MAOi antidepressants prevent REM entirely (without any noticeable ill-effects, suggesting REM is dispensable). SSRIs only partially suppress it.

Ironically, SSRIs can make dreams more vivid and colourful. I've been told by sleep scientists that this is because they delay the onset of REM so the dreams are "shifted" later into the night making you more likely to remember them when you wake up. But there could be more to it than that.

The fact that REM is a serotonin-free zone also explains wet dreams. Serotonin is well known to suppresses ejaculation; that's why SSRIs delay orgasm, one of their least popular side effects, although it's useful to treat premature ejaculation: every cloud has a silver lining.

So, having said all that: could this also explain the terror of early-morning waking? Suppose that, for whatever reason, you woke up during REM sleep, but your serotonin cells didn't wake up quick enough, leaving you awake, but with no serotonin (a situation which never normally occurs, remember). How would that feel?

Using a technique called acute tryptophan depletion (ATD), you can lower someone's serotonin levels. In most people, this doesn't do very much, but in some people with a history of depression, it causes them to relapse. Here's what happened to one patient after ATD:

[her] previous episodes of clinical depression were associated with the loss of important friendships had, while depressed, been preoccupied with fears that she would never be able to sustain a relationship. She had not had such fears since then.

She had been fully recovered and had not taken any medication for over a year. About 2 h after drinking the tryptophan-free mixture she experienced a sudden onset of sadness, despair, and uncontrollable crying. She feared that a current important relationship would end.

We don't know why tryptophan depletion does this to some people, or why it doesn't affect everyone the same way, and it's pure speculation that early morning waking has anything to do with this. But having said that, the pieces do seem to fit.

Blue Morning

Recently, I wrote about diurnal mood variation: the way in which depression often waxes and wanes over the course of the day. Mornings are generally the worst.

A related phenomenon is late insomnia, or "early morning waking".

But this phrase is rather an understatement. Everyone's woken up early. Maybe you had a flight to catch. Or you were drunk and threw up. Or you just needed a pee. That's early morning waking, but not the depressive kind. When you're depressed, the waking up is the least of your problems.

Suddenly, you are awake, more awake than you've ever been. And you know something terrible has happened, or is about to happen, or that you've done something terribly wrong. It feels like a Eureka moment. You can be a level-headed person, not given to jumping to conclusions, but you will be convinced of this.

In a panic attack, you think you're going to die. Your heart is beating too fast, your breathing's too deep: your body is exploding, you can feel it too closely. With this, With this, you think you should die or even, in some sense, already have. It feels cold: you can no longer feel the warmth of your own body.

The moment passes; the terrible truth that you were so certain of five minutes ago becomes a little doubtful. Maybe it's not quite so bad. At this point, the wakefulness goes too, and you become, well, as tired as you ought to be at 3 am. You try to go back to sleep. If you're lucky, you succeed. If not, you lie awake until morning in a state of miserable contemplation.

While it's happening, you think that you're going to feel this way forever; bizarrely, you think you always have felt this way. In fact, this is the darkest hour.

*

Why does this happen? There has been almost no research on early morning waking. Presumably, because it's so hard to study. To observe it, you would have to get your depressed patients to spend all night in your brain scanner (or, if you prefer, on your analyst's couch), and even then, it doesn't happen every night.

But here's my theory: the key is the biology of sleep. There are many stages of sleep; at a very rough approximation there's dreaming REM, and dreamless slow-wave. Now, REM sleep tends to happen during the second half of the night - the early morning.

During REM sleep, the brain is, in many respects, awake. This is presumably what allows us to have concious dreams. Whereas in slow wave sleep, the brain really is offline; slow waves are also seen in the brain of people in comas, or under deep anaesthesia.

When we're awake, the brain is awash with modulatory neurotransmitters, such as serotonin, norepinephrine, and acetylcholine. During REM, acetylcholine is present, while in slow-wave sleep it's not; indeed acetylcholine may well be what stops slow waves and "wakes up" the cortex.

But unlike during waking, serotonin and norepinephrine neurons are entirely inactive during REM sleep - and only during REM sleep. This fact is surprisingly little-known, but it seems to me that it explains an awful lot.

For one thing, it explains why drugs which increase serotonin levels, such as SSRI antidepressants, inhibit REM sleep. Indeed, high doses of MAOi antidepressants prevent REM entirely (without any noticeable ill-effects, suggesting REM is dispensable). SSRIs only partially suppress it.

Ironically, SSRIs can make dreams more vivid and colourful. I've been told by sleep scientists that this is because they delay the onset of REM so the dreams are "shifted" later into the night making you more likely to remember them when you wake up. But there could be more to it than that.

The fact that REM is a serotonin-free zone also explains wet dreams. Serotonin is well known to suppresses ejaculation; that's why SSRIs delay orgasm, one of their least popular side effects, although it's useful to treat premature ejaculation: every cloud has a silver lining.

So, having said all that: could this also explain the terror of early-morning waking? Suppose that, for whatever reason, you woke up during REM sleep, but your serotonin cells didn't wake up quick enough, leaving you awake, but with no serotonin (a situation which never normally occurs, remember). How would that feel?

Using a technique called acute tryptophan depletion (ATD), you can lower someone's serotonin levels. In most people, this doesn't do very much, but in some people with a history of depression, it causes them to relapse. Here's what happened to one patient after ATD:

[her] previous episodes of clinical depression were associated with the loss of important friendships had, while depressed, been preoccupied with fears that she would never be able to sustain a relationship. She had not had such fears since then.

She had been fully recovered and had not taken any medication for over a year. About 2 h after drinking the tryptophan-free mixture she experienced a sudden onset of sadness, despair, and uncontrollable crying. She feared that a current important relationship would end.

We don't know why tryptophan depletion does this to some people, or why it doesn't affect everyone the same way, and it's pure speculation that early morning waking has anything to do with this. But having said that, the pieces do seem to fit.

The Hunt for the Prozac Gene

One of the difficulties doctors face when prescribing antidepressants is that they're unpredictable.

One person might do well on a certain drug, but the next person might get no benefit from the exact same pills. Finding the right drug for each patient is often a matter of trying different ones until one works.

So a genetic test to work out whether a certain drug will help a particular person would be really useful. Not to mention really profitable for whoever patented it. Three recent papers, published in three major journals, all claim to have found genes that predict antidepressant response. Great! The problem is, they were different genes.

First up, American team Binder et al looked at about 200 variants in 10 genes involved in the corticosteroid stress response pathway. They found one, in a gene called CRHBP, that was significantly associated with poor response to the popular SSRI antidepressant citalopram (Celexa), using the large STAR*D project data set. But this was only true of African-Americans and Latinos, not whites.

Garriock et al used the exact same dataset, but they did a genome-wide association study (GWAS), which looks at variants across the whole genome, unlike Binder et al who focussed on a small number of specific candidate genes. Sadly no variants were statistically significantly correlated with response to citalopram, although in a GWAS, the threshold for genome-wide significance is very high due to multiple comparisons correction. Some were close to being significant, but they weren't obviously related to CRHBP, and most weren't anything to do with the brain.

Uher et al did another GWAS of response to escitalopram and nortriptyline in a different sample, the European GENDEP study. Escitalopram is extremely similar to citalopram, the drug in the STAR*D studies; nortriptyline however is very different. They found one genome-wide significant hit. A variant in a gene called UST was associated with response to nortriptyline, but not escitalopram. No variants were associated with response to escitalopram, although one in the gene IL11 was close. There were some other nearly-significant results, but they didn't overlap with either of the STAR*D studies.

Finally, one of the STAR*D studies found a variant significantly linked to tolerability (side effects) of citalopram. GENDEP didn't look at this.

*

The UST link to nortriptyline finding is the strongest thing here, but for citalopram / escitalopram, no consistent pharmacogenetic results emerged at all. What does this mean? Well, it's possible that there just aren't any genes for citalopram response, but that seems unlikely. Even if you believe that antidepressants only work as placebos, you'd expect there would be genes that alter placebo responses, or at the very least, that affect side-effects and hence the active placebo improvement.

The thing is that the "antidepressant response" in these studies isn't really that: it's a mix of many factors. We know that a lot of the improvement would have happened even with placebo pills, so much of it isn't a pharmacological effect. There are probably genes associated with placebo improvement, but they might not be the same ones that are associated with drug improvement and a gene might even have opposite effects that cancel out (better drug effect, worse placebo effect). Some of the recorded improvement won't even be real improvement at all, just people saying they feel better because they know they're expected to.

If I were looking for the genes for SSRI response, not that I plan to, here's what I'd do. To stack the odds in my favour, I'd forget people with an moderate or partial response, and focus on those who either do really well, or those who get no benefit at all, with a certain drug. I'd also want to exclude people who respond really well, but not due to the specific effects of the drug.

That would be hard but one angle would be to only include people whose improvement is specifically reversed by acute tryptophan depletion, which reduces serotonin levels thus counteracting SSRIs. This would be a hard study to do, though not impossible. (In fact there are dozens of patients on record who meet my criteria, and their blood samples are probably still sitting in freezers in labs around the world... maybe someone should dig them out).

Still, even if you did find some genes that way, would they be useful? We'd have had to go to such lengths to find them, that they're not going to help doctors decide what to do with the average patient who comes through the door with depression. That's true, but they might just help us to work out who will respond to SSRIs, as opposed to other drugs.

Binder EB, Owens MJ, Liu W, Deveau TC, Rush AJ, Trivedi MH, Fava M, Bradley B, Ressler KJ, & Nemeroff CB (2010). Association of polymorphisms in genes regulating the corticotropin-releasing factor system with antidepressant treatment response. Archives of general psychiatry, 67 (4), 369-79 PMID: 20368512

Uher, R., Perroud, N., Ng, M., Hauser, J., Henigsberg, N., Maier, W., Mors, O., Placentino, A., Rietschel, M., Souery, D., Zagar, T., Czerski, P., Jerman, B., Larsen, E., Schulze, T., Zobel, A., Cohen-Woods, S., Pirlo, K., Butler, A., Muglia, P., Barnes, M., Lathrop, M., Farmer, A., Breen, G., Aitchison, K., Craig, I., Lewis, C., & McGuffin, P. (2010). Genome-Wide Pharmacogenetics of Antidepressant Response in the GENDEP Project American Journal of Psychiatry DOI: 10.1176/appi.ajp.2009.09070932

Garriock, H., Kraft, J., Shyn, S., Peters, E., Yokoyama, J., Jenkins, G., Reinalda, M., Slager, S., McGrath, P., & Hamilton, S. (2010). A Genomewide Association Study of Citalopram Response in Major Depressive Disorder Biological Psychiatry, 67 (2), 133-138 DOI: 10.1016/j.biopsych.2009.08.029

The Hunt for the Prozac Gene

One of the difficulties doctors face when prescribing antidepressants is that they're unpredictable.

One person might do well on a certain drug, but the next person might get no benefit from the exact same pills. Finding the right drug for each patient is often a matter of trying different ones until one works.

So a genetic test to work out whether a certain drug will help a particular person would be really useful. Not to mention really profitable for whoever patented it. Three recent papers, published in three major journals, all claim to have found genes that predict antidepressant response. Great! The problem is, they were different genes.

First up, American team Binder et al looked at about 200 variants in 10 genes involved in the corticosteroid stress response pathway. They found one, in a gene called CRHBP, that was significantly associated with poor response to the popular SSRI antidepressant citalopram (Celexa), using the large STAR*D project data set. But this was only true of African-Americans and Latinos, not whites.

Garriock et al used the exact same dataset, but they did a genome-wide association study (GWAS), which looks at variants across the whole genome, unlike Binder et al who focussed on a small number of specific candidate genes. Sadly no variants were statistically significantly correlated with response to citalopram, although in a GWAS, the threshold for genome-wide significance is very high due to multiple comparisons correction. Some were close to being significant, but they weren't obviously related to CRHBP, and most weren't anything to do with the brain.

Uher et al did another GWAS of response to escitalopram and nortriptyline in a different sample, the European GENDEP study. Escitalopram is extremely similar to citalopram, the drug in the STAR*D studies; nortriptyline however is very different. They found one genome-wide significant hit. A variant in a gene called UST was associated with response to nortriptyline, but not escitalopram. No variants were associated with response to escitalopram, although one in the gene IL11 was close. There were some other nearly-significant results, but they didn't overlap with either of the STAR*D studies.

Finally, one of the STAR*D studies found a variant significantly linked to tolerability (side effects) of citalopram. GENDEP didn't look at this.

*

The UST link to nortriptyline finding is the strongest thing here, but for citalopram / escitalopram, no consistent pharmacogenetic results emerged at all. What does this mean? Well, it's possible that there just aren't any genes for citalopram response, but that seems unlikely. Even if you believe that antidepressants only work as placebos, you'd expect there would be genes that alter placebo responses, or at the very least, that affect side-effects and hence the active placebo improvement.

The thing is that the "antidepressant response" in these studies isn't really that: it's a mix of many factors. We know that a lot of the improvement would have happened even with placebo pills, so much of it isn't a pharmacological effect. There are probably genes associated with placebo improvement, but they might not be the same ones that are associated with drug improvement and a gene might even have opposite effects that cancel out (better drug effect, worse placebo effect). Some of the recorded improvement won't even be real improvement at all, just people saying they feel better because they know they're expected to.

If I were looking for the genes for SSRI response, not that I plan to, here's what I'd do. To stack the odds in my favour, I'd forget people with an moderate or partial response, and focus on those who either do really well, or those who get no benefit at all, with a certain drug. I'd also want to exclude people who respond really well, but not due to the specific effects of the drug.

That would be hard but one angle would be to only include people whose improvement is specifically reversed by acute tryptophan depletion, which reduces serotonin levels thus counteracting SSRIs. This would be a hard study to do, though not impossible. (In fact there are dozens of patients on record who meet my criteria, and their blood samples are probably still sitting in freezers in labs around the world... maybe someone should dig them out).

Still, even if you did find some genes that way, would they be useful? We'd have had to go to such lengths to find them, that they're not going to help doctors decide what to do with the average patient who comes through the door with depression. That's true, but they might just help us to work out who will respond to SSRIs, as opposed to other drugs.

Binder EB, Owens MJ, Liu W, Deveau TC, Rush AJ, Trivedi MH, Fava M, Bradley B, Ressler KJ, & Nemeroff CB (2010). Association of polymorphisms in genes regulating the corticotropin-releasing factor system with antidepressant treatment response. Archives of general psychiatry, 67 (4), 369-79 PMID: 20368512

Uher, R., Perroud, N., Ng, M., Hauser, J., Henigsberg, N., Maier, W., Mors, O., Placentino, A., Rietschel, M., Souery, D., Zagar, T., Czerski, P., Jerman, B., Larsen, E., Schulze, T., Zobel, A., Cohen-Woods, S., Pirlo, K., Butler, A., Muglia, P., Barnes, M., Lathrop, M., Farmer, A., Breen, G., Aitchison, K., Craig, I., Lewis, C., & McGuffin, P. (2010). Genome-Wide Pharmacogenetics of Antidepressant Response in the GENDEP Project American Journal of Psychiatry DOI: 10.1176/appi.ajp.2009.09070932

Garriock, H., Kraft, J., Shyn, S., Peters, E., Yokoyama, J., Jenkins, G., Reinalda, M., Slager, S., McGrath, P., & Hamilton, S. (2010). A Genomewide Association Study of Citalopram Response in Major Depressive Disorder Biological Psychiatry, 67 (2), 133-138 DOI: 10.1016/j.biopsych.2009.08.029

Life Without Serotonin

Via Dormivigilia, I came across a fascinating paper about a man who suffered from a severe lack of monoamine neurotransmitters (dopamine, serotonin etc.) as a result of a genetic mutation: Sleep and Rhythm Consequences of a Genetically Induced Loss of Serotonin


Neuroskeptic readers will be familiar with monoamines. They're psychiatrists' favourite neurotransmitters, and are hence very popular amongst psych drug manufacturers. In particular, it's widely believed that serotonin is the brain's "happy chemical" and that clinical depression is caused by low serotonin while antidepressants work by boosting it.

Critics charge that there is no evidence for any of this. My own opinion is that it's complicated, but that while there's certainly no simple relation between serotonin, antidepressants and mood, they are linked in some way. It's all rather mysterious, but then, the functions of serotonin in general are; despite 50 years of research, it's probably the least understood neurotransmitter.

The new paper adds to the mystery, but also provides some important new data. Leu-Semenescu et al report on the case of a 28 year old man, with consanguineous parents, who suffers from a rare genetic disorder, sepiapterin reductase deficiency (SRD). SRD patients lack an enzyme which is involved, indirectly, in the production of the monoamines serotonin and dopamine, and also melatonin and noradrenaline which are produced from these two. SRD causes a severe (but not total) deficiency of these neurotransmitters.

The most obvious symptoms of SRD are related to the lack of dopamine, and include poor coordination and weakness, very similar to Parkinson's Disease. An interesting feature of SRD is that these symptoms are mild in the morning, worsen during the day, and improve with sleep. Such diurnal variation is also a hallmark of severe depression, although in depression it's usually the other way around (better in the evening).

The patient reported on in this paper suffered Parkinsonian symptoms from birth, until he was diagnosed with dystonia at age 5 and started on L-dopa to boost his dopamine levels. This immediately and dramatically reversed the problems.

But his serotonin synthesis was still impaired, although doctors didn't realize this until age 27. As a result, Leu-Semenescu et al say, he suffered from a range of other, non-dopamine-related symptoms. These included increased appetite - he ate constantly, and was moderately obese - mild cognitive impairment, and disrupted sleep:

The patient reported sleep problems since childhood. He would sleep 1 or 2 times every day since childhood and was awake during more than 2 hours most nights since adolescence. At the time of the first interview, the night sleep was irregular with a sleep onset at 22:00 and offset between 02:00 and 03:00. He often needed 1 or 2 spontaneous, long (2- to 5-h) naps during the daytime.

After doctors did a genetic test and diagnosed SRD, they treated him with 5HTP, a precursor to serotonin. The patient's sleep cycle immediately normalized, his appetite was reduced and his concentration and cognitive function improved (although that may have been because he was less tired). Here's his before and after hypnogram:

Disruptions in sleep cycle and appetite are likewise common in clinical depression. The direction of the changes in depression varies: loss of appetite is common in the most severe "melancholic" depression, while increased appetite is seen in many other people.

For sleep, both daytime sleepiness and night-time insomnia, especially waking up too early, can occur in depression. The most interesting parallel here is that people with depression often show a faster onset of REM (dreaming) sleep, which was also seen in this patient before 5HTP treatment. However, it's not clear what was due to serotonin and what was due to melatonin because melatonin is known to regulate sleep.

Overall, though, the biggest finding here was a non-finding: this patient wasn't depressed, despite having much reduced serotonin levels. This is further evidence that serotonin isn't the "happy chemical" in any simple sense.

On the other hand, the similarities between his symptoms and some of the symptoms of depression suggest that serotonin is doing something in that disorder. This fits with existing evidence from tryptophan depletion studies showing that low serotonin doesn't cause depression in most people, but does re-activate symptoms in people with a history of the disease. As I said, it's complicated...

Smaranda Leu-Semenescu et al. (2010). Sleep and Rhythm Consequences of a Genetically Induced Loss of Serotonin Sleep, 33 (03), 307-314

Life Without Serotonin

Via Dormivigilia, I came across a fascinating paper about a man who suffered from a severe lack of monoamine neurotransmitters (dopamine, serotonin etc.) as a result of a genetic mutation: Sleep and Rhythm Consequences of a Genetically Induced Loss of Serotonin


Neuroskeptic readers will be familiar with monoamines. They're psychiatrists' favourite neurotransmitters, and are hence very popular amongst psych drug manufacturers. In particular, it's widely believed that serotonin is the brain's "happy chemical" and that clinical depression is caused by low serotonin while antidepressants work by boosting it.

Critics charge that there is no evidence for any of this. My own opinion is that it's complicated, but that while there's certainly no simple relation between serotonin, antidepressants and mood, they are linked in some way. It's all rather mysterious, but then, the functions of serotonin in general are; despite 50 years of research, it's probably the least understood neurotransmitter.

The new paper adds to the mystery, but also provides some important new data. Leu-Semenescu et al report on the case of a 28 year old man, with consanguineous parents, who suffers from a rare genetic disorder, sepiapterin reductase deficiency (SRD). SRD patients lack an enzyme which is involved, indirectly, in the production of the monoamines serotonin and dopamine, and also melatonin and noradrenaline which are produced from these two. SRD causes a severe (but not total) deficiency of these neurotransmitters.

The most obvious symptoms of SRD are related to the lack of dopamine, and include poor coordination and weakness, very similar to Parkinson's Disease. An interesting feature of SRD is that these symptoms are mild in the morning, worsen during the day, and improve with sleep. Such diurnal variation is also a hallmark of severe depression, although in depression it's usually the other way around (better in the evening).

The patient reported on in this paper suffered Parkinsonian symptoms from birth, until he was diagnosed with dystonia at age 5 and started on L-dopa to boost his dopamine levels. This immediately and dramatically reversed the problems.

But his serotonin synthesis was still impaired, although doctors didn't realize this until age 27. As a result, Leu-Semenescu et al say, he suffered from a range of other, non-dopamine-related symptoms. These included increased appetite - he ate constantly, and was moderately obese - mild cognitive impairment, and disrupted sleep:

The patient reported sleep problems since childhood. He would sleep 1 or 2 times every day since childhood and was awake during more than 2 hours most nights since adolescence. At the time of the first interview, the night sleep was irregular with a sleep onset at 22:00 and offset between 02:00 and 03:00. He often needed 1 or 2 spontaneous, long (2- to 5-h) naps during the daytime.

After doctors did a genetic test and diagnosed SRD, they treated him with 5HTP, a precursor to serotonin. The patient's sleep cycle immediately normalized, his appetite was reduced and his concentration and cognitive function improved (although that may have been because he was less tired). Here's his before and after hypnogram:

Disruptions in sleep cycle and appetite are likewise common in clinical depression. The direction of the changes in depression varies: loss of appetite is common in the most severe "melancholic" depression, while increased appetite is seen in many other people.

For sleep, both daytime sleepiness and night-time insomnia, especially waking up too early, can occur in depression. The most interesting parallel here is that people with depression often show a faster onset of REM (dreaming) sleep, which was also seen in this patient before 5HTP treatment. However, it's not clear what was due to serotonin and what was due to melatonin because melatonin is known to regulate sleep.

Overall, though, the biggest finding here was a non-finding: this patient wasn't depressed, despite having much reduced serotonin levels. This is further evidence that serotonin isn't the "happy chemical" in any simple sense.

On the other hand, the similarities between his symptoms and some of the symptoms of depression suggest that serotonin is doing something in that disorder. This fits with existing evidence from tryptophan depletion studies showing that low serotonin doesn't cause depression in most people, but does re-activate symptoms in people with a history of the disease. As I said, it's complicated...

Smaranda Leu-Semenescu et al. (2010). Sleep and Rhythm Consequences of a Genetically Induced Loss of Serotonin Sleep, 33 (03), 307-314

Predicting Antidepressant Response with EEG

One of the limitations of antidepressants is that they don't always work. Worse, they don't work in an unpredictable way. Some people benefit from some drugs, and others don't, but there's no way of knowing in advance what will happen in any particular case - or of telling which pill is right for which person.

As a result, drug treatment for depression generally involves starting with a cheap medication with relatively mild side-effects, and if that fails, moving onto a series of other drugs until one helps. But since it can take several weeks for any new drug to work, this can be a frustrating process for patients and doctors alike.

Some means of predicting the antidepressant response would thus be very useful. Many have been proposed, but none have entered widespread clinical use. Now, a pair of papers(1,2) from UCLA's Andrew Leuchter et al make the case for prediction using quantitative EEG (QEEG).

EEG, electroencephalography, is a crude but effective way of recording electrical activity in the brain via electrodes attached to the head. "Quantitative" EEG just means using EEG to precisely measure the level of certain kinds of activity in the brain.

Leuchter et al's system is straightforward: it uses six electrodes on the front of the head. The patient simply relaxes with their eyes closed for a few minutes while neural activity is recorded.

This procedure is performed twice, once just before antidepressant treatment begins and then again a week later. The claim is that by examining the changes in the EEG signal after one week of drug treatment, the eventual benefit of the drug can be predicted. It's not an implausible idea, and if it did work, it would be rather helpful. But does it?

Leuchter et al say: yes! The first paper reports that in 73 depressed patients who were given the antidepressant escitalopram 10mg/day, QEEG changes after one week predicted clinical improvement six weeks later. Specifically, people who got substantially better at seven weeks had a higher "Antidepressant Treatment Response Index" (ATR) at one week than people who didn't: 59.0 ± 10.2 vs 49.8 ± 7.8, which is highly significant (p less than 0.001).

In the companion paper, the authors examined patients who started on escitalopram and then either kept taking it or switched to a different antidepressant, bupropion. They found that patients who had a high ATR after a week of escitalopram tended to do well if they stayed on it, while patients who had a low ATR to escitalopram did better when they switched to the other drug.

These are interesting results, and they follow from ten years of previous work (mostly, but not exclusively, from the same group) on the topic. Because the current study didn't include a placebo group, we can't say that the QEEG predicts antidepressant response as such, only that it predicts improvement in depression symptoms. But even this is pretty exciting, if it really works.

In order to verify that it does, other researchers need to replicate this experiment. But they may find this a little difficult. What is the Antidepressant Treatment Response Index use in this study? It's derived from an analysis of the EEG signal, and we're told that you get it from this formula:

Some of the terms here are common parameters that any EEG expert will understand. But "A", "B", and "C" are not. They're constants, which are not given in the paper. They're secret numbers. Without knowing what those numbers are, no-one can calculate the "ATR" even if they have an EEG machine.

Why keep them secret? Well...

"Financial support of this project was provided by Aspect Medical Systems. Aspect participated in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation and review of the manuscript."

Aspect is a large medical electronics company who developed the system used here. Presumably, they want to patent it (or already have). We're told that

"To facilitate independent replication of the work reported here, Aspect intends to make available a limited number of investigational systems for academic researchers. Please contact Scott Greenwald, Ph.D... for further information."

All very nice of them, but if they'd told us the three magic numbers, academics could start trying to independently replicate these results tomorrow. As it is, anyone who wants to do so will have to get Aspect's blessing, which, with the best will in the world, means they will not be entirely "independent".

[BPSDB]

Leuchter AF, Cook IA, Gilmer WS, Marangell LB, Burgoyne KS, Howland RH, Trivedi MH, Zisook S, Jain R, Fava M, Iosifescu D, & Greenwald S (2009). Effectiveness of a quantitative electroencephalographic biomarker for predicting differential response or remission with escitalopram and bupropion in major depressive disorder. Psychiatry research PMID: 19709754

Leuchter AF, Cook IA, Marangell LB, Gilmer WS, Burgoyne KS, Howland RH, Trivedi MH, Zisook S, Jain R, McCracken JT, Fava M, Iosifescu D, & Greenwald S (2009). Comparative effectiveness of biomarkers and clinical indicators for predicting outcomes of SSRI treatment in Major Depressive Disorder: Results of the BRITE-MD study. Psychiatry research PMID: 19712979