Friday, December 26, 2008

Seven Things You Didn't Know About Milgram

There's been a lot written about psychology professor Jerry Burger's recent replication of the famous "obedience" experiments first carried out by Stanley Milgram in the early 1960s. Here's Burger's paper in which he reports that obedience rates are almost the same today as they were nearly 50 years ago.

Wikipedia's page on this experiment has an excellent summary of the methodology and results of the original study if you're not familiar with it.

It's a testament to the importance of the original obedience experiment that many who know nothing else about psychology have at least heard of it, and it's common knowledge that Milgram found that a startlingly high proportion of ordinary volunteers were willing to administer very strong "shocks" to an innocent victim, on the orders of the experimenter. But there's much more to the "Milgram Experiment" than many people realize. So - read on. That's an order.
  1. There wasn't just one experiment In 1974, Milgram discussed the results and implications of his research in a book, Obedience to Authority: An Experimental View. (The cover is rather amusing). In it he describes no fewer than 19 different experiments, not including pilot studies. Most of the studies included 40 participants, although some of the later ones used 20. The basic nature of the experimental situation was the same in each case, but important factors were varied between expriments, offering some insight into the conditions which drive obedience (see below). All of this work was performed at or near Yale between 1960 and 1963. Milgram also refers to later replication studies carried out in"Princeton, Munich, Rome, South Africa and Australia" where "the level of obedience was invariably somewhat higher than that found [in the Yale studies]". So, whatever was going on in the Milgram experiments, it wasn't unique to the USA, and the fact that Jerry Burger has just obtained very similar results shows that it wasn't unique to the 1960s either (although, to look at it the other way, the USA today is not especially conformist.)
  2. Subjects were paid $4 each Milgram's book is full of details such as this, including plenty of photos and drawings illustrating what happened. The picture here shows the designated "victim" in most of the experiments - James McDonough, "a 47-year old accountant, trained for the role; he was of Irish-American descent and most observers found him mild-mannered and affable". This is the face that launched a thousand shocks - seeing it, for me, brought home the results of the obedience studies very starkly. How could anyone shock that guy? Another important detail is that rather than recruiting undergraduate students, as most psychology experiments do, Milgram placed adverts in local newspapers and, when that only got a few hundred volunteers, resorted to cold-calling names in the New Haven telephone directory. This meant that the participants were (as far as possible) representative of the normal population - a crucial point.
  3. Milgram was an Evolutionary Psychologist Well, sort of. He was into Evolutionary Psychology before it became a buzzphrase - indeed, before the term had been coined. In his book, Milgram notes that "the formation of hierarchically organised groupings lends enormous advantage to those so organized in coping with dangers of the physical environment, threats posed by competing species, and potential disruption from within." In other words, an animal which has the ability to submit to authority when necessary might be more likely to survive than one which was stubbornly individualistic. He goes on to theorize that humans have evolved a psychological mechanism for obedience, which he calls the "Agentic State", a special state of mind in which our normal moral inhibitions are bypassed and we become an agent of an authority. I'm not sure many people would buy this as a good explanation, and it isn't clear if Milgram's evolutionary logic relies on Group Selection theory, but it's certainly interesting.
  4. It was stressful Most of the subjects were acutely distressed during the procedure - hardly surprising given the screams and protests of their "victim". Some subjects shook with tension; one started laughing whenever they had to give a shock. Yet most of them continued to give the shocks despite being tangibly upset about it. They didn't want to hurt the "victim" - but they did. This inner conflict suffered by the subjects comes across vividly in Milgram's writing, and it led to some fascinating behaviour. In Experiment 7, in which the "experimenter" giving orders left the room and spoke to the subjects by telephone, many subjects continued to give shocks but gave much milder shocks than they were supposed to. In other words, they were unwilling to hurt the victim but also unwilling to openly disobey (although in this case, 80% of subjects eventually did). Most people also seemed to try to keep the shocks as short as possible, and tried to minimize the number of punishments by helping the victim to give the right answers. Milgram argued that this ruled out the view that his experiment showed people to be "aggressive" or "sadistic" - rather, people were naturally averse to causing harm, but the situation they found themselves in led them to do so anyway. As he put it "The social psychology of this century reveals a major lesson: often it is not so much the kind of person a man as the kind of situation in which he finds himself that determines how he will act."
  5. There was follow-up Milgram's sometimes accused of being a cavalier or even callous researcher who exposed his volunteers to emotional harm. In fact although, as the cliche goes, Milgram's studies would never pass an ethics committee today, he seems (at least on his own account) to have gone to great effort to ensure that his participants were not traumatized and to record how they felt about the experiment. Immediately after the experiment was finished the subjects were "debriefed" and told what had really happened; if they had been obedient, they were reassured that this was normal behaviour (true, of course). Then, a few weeks later, they were sent a write-up of the results of the research and an explanation of the rationale. A questionairre asked how they felt about the study overall; 43% said they were very glad to have done it, 40% said they were glad, and just 1.3% were sorry or very sorry to have done it; there was little difference between those who obeyed and those who didn't. Commenting on the fact that people seemed remarkably relaxed about what they had done, in retrospect, Milgram wryly noted "The same mechanisms that allow the subject to perform the act...continue to justify his behaviour for him".
  6. Not everyone obeyed You probably already know this, but you think of it as less exciting than the fact that most people did. In the best known version of the experiment (Experiment 5), 35% of people refused to administer the highest shock level, and some of those came close to it. In other experimental set-ups, obedience rates were different - when the study was carried out in a run-down city apartment, rather than in the presitgous surroundings of Yale, obedience rates dropped (but were still 47.5%). When the subjects did not have to administer the shocks themselves but simply sit by and take notes while someone else did, almost everyone complied (92.5%). Yet there were no clear explanations for why some individuals obeyed and some did not. Some people were chillingly obedient, others were boldly defiant, but it's not clear why. Age, religion (Catholic vs. Protestant), and political affiliation did not seem to matter. Most of the studies used male volunteers only, for some reason, but Experiment 8 used women; compared to Experiment 5 the results were pretty much identical. In the early experiments there were some indications that better educated and higher-status men were more defiant, but this did not seem to hold for all of the studies.
  7. This actually happened Again, you already knew this, but it's worth taking a moment to remember it. This really happened and it's been replicated ad nauseum; so far as I can see, no-one has succesfully criticized the basic assumptions of the paradigm (although if anyone has please let me know.) Milgram's faith in humanity seems to have been shaken by his research - his book contains case studies of individual participants which are are cynical to the point of misanthropy, even down to the level of the physical appearance and personality of the participants ("Mr Batta is a 37-year old welder...he has a rough-hewn face that conveys a conspicuous lack of alertness. His overall appearance is somewhat brutish...[during the experiment] what is remarkable is his total indifference to the learner; he hardly takes cognizance of him as a human being...the scene is brutal and depressing...at the end of the session he tells the experimenter how honored he has been to help him.") The subjects who disobeyed authority get a slightly better treatment, but not much better. Yet who can blame Milgram for this? It's worth bearing in mind also that Milgram was Jewish. His text is full of references to Nazi Germany, Hannah Arendt, the Vietnam War and the Mai Lai massacre. The hero of the book, if there is one, seems to be the young man who took part in the experiment and, as a result, decided to apply for Conscientous Objector status to avoid being sent to Vietnam. He got it.
Links: Dr Thomas Blass's StanleyMilgram.com - excellent.
Dr Blass's review paper on the Milgram paradigm.

Seven Things You Didn't Know About Milgram

There's been a lot written about psychology professor Jerry Burger's recent replication of the famous "obedience" experiments first carried out by Stanley Milgram in the early 1960s. Here's Burger's paper in which he reports that obedience rates are almost the same today as they were nearly 50 years ago.

Wikipedia's page on this experiment has an excellent summary of the methodology and results of the original study if you're not familiar with it.

It's a testament to the importance of the original obedience experiment that many who know nothing else about psychology have at least heard of it, and it's common knowledge that Milgram found that a startlingly high proportion of ordinary volunteers were willing to administer very strong "shocks" to an innocent victim, on the orders of the experimenter. But there's much more to the "Milgram Experiment" than many people realize. So - read on. That's an order.
  1. There wasn't just one experiment In 1974, Milgram discussed the results and implications of his research in a book, Obedience to Authority: An Experimental View. (The cover is rather amusing). In it he describes no fewer than 19 different experiments, not including pilot studies. Most of the studies included 40 participants, although some of the later ones used 20. The basic nature of the experimental situation was the same in each case, but important factors were varied between expriments, offering some insight into the conditions which drive obedience (see below). All of this work was performed at or near Yale between 1960 and 1963. Milgram also refers to later replication studies carried out in"Princeton, Munich, Rome, South Africa and Australia" where "the level of obedience was invariably somewhat higher than that found [in the Yale studies]". So, whatever was going on in the Milgram experiments, it wasn't unique to the USA, and the fact that Jerry Burger has just obtained very similar results shows that it wasn't unique to the 1960s either (although, to look at it the other way, the USA today is not especially conformist.)
  2. Subjects were paid $4 each Milgram's book is full of details such as this, including plenty of photos and drawings illustrating what happened. The picture here shows the designated "victim" in most of the experiments - James McDonough, "a 47-year old accountant, trained for the role; he was of Irish-American descent and most observers found him mild-mannered and affable". This is the face that launched a thousand shocks - seeing it, for me, brought home the results of the obedience studies very starkly. How could anyone shock that guy? Another important detail is that rather than recruiting undergraduate students, as most psychology experiments do, Milgram placed adverts in local newspapers and, when that only got a few hundred volunteers, resorted to cold-calling names in the New Haven telephone directory. This meant that the participants were (as far as possible) representative of the normal population - a crucial point.
  3. Milgram was an Evolutionary Psychologist Well, sort of. He was into Evolutionary Psychology before it became a buzzphrase - indeed, before the term had been coined. In his book, Milgram notes that "the formation of hierarchically organised groupings lends enormous advantage to those so organized in coping with dangers of the physical environment, threats posed by competing species, and potential disruption from within." In other words, an animal which has the ability to submit to authority when necessary might be more likely to survive than one which was stubbornly individualistic. He goes on to theorize that humans have evolved a psychological mechanism for obedience, which he calls the "Agentic State", a special state of mind in which our normal moral inhibitions are bypassed and we become an agent of an authority. I'm not sure many people would buy this as a good explanation, and it isn't clear if Milgram's evolutionary logic relies on Group Selection theory, but it's certainly interesting.
  4. It was stressful Most of the subjects were acutely distressed during the procedure - hardly surprising given the screams and protests of their "victim". Some subjects shook with tension; one started laughing whenever they had to give a shock. Yet most of them continued to give the shocks despite being tangibly upset about it. They didn't want to hurt the "victim" - but they did. This inner conflict suffered by the subjects comes across vividly in Milgram's writing, and it led to some fascinating behaviour. In Experiment 7, in which the "experimenter" giving orders left the room and spoke to the subjects by telephone, many subjects continued to give shocks but gave much milder shocks than they were supposed to. In other words, they were unwilling to hurt the victim but also unwilling to openly disobey (although in this case, 80% of subjects eventually did). Most people also seemed to try to keep the shocks as short as possible, and tried to minimize the number of punishments by helping the victim to give the right answers. Milgram argued that this ruled out the view that his experiment showed people to be "aggressive" or "sadistic" - rather, people were naturally averse to causing harm, but the situation they found themselves in led them to do so anyway. As he put it "The social psychology of this century reveals a major lesson: often it is not so much the kind of person a man as the kind of situation in which he finds himself that determines how he will act."
  5. There was follow-up Milgram's sometimes accused of being a cavalier or even callous researcher who exposed his volunteers to emotional harm. In fact although, as the cliche goes, Milgram's studies would never pass an ethics committee today, he seems (at least on his own account) to have gone to great effort to ensure that his participants were not traumatized and to record how they felt about the experiment. Immediately after the experiment was finished the subjects were "debriefed" and told what had really happened; if they had been obedient, they were reassured that this was normal behaviour (true, of course). Then, a few weeks later, they were sent a write-up of the results of the research and an explanation of the rationale. A questionairre asked how they felt about the study overall; 43% said they were very glad to have done it, 40% said they were glad, and just 1.3% were sorry or very sorry to have done it; there was little difference between those who obeyed and those who didn't. Commenting on the fact that people seemed remarkably relaxed about what they had done, in retrospect, Milgram wryly noted "The same mechanisms that allow the subject to perform the act...continue to justify his behaviour for him".
  6. Not everyone obeyed You probably already know this, but you think of it as less exciting than the fact that most people did. In the best known version of the experiment (Experiment 5), 35% of people refused to administer the highest shock level, and some of those came close to it. In other experimental set-ups, obedience rates were different - when the study was carried out in a run-down city apartment, rather than in the presitgous surroundings of Yale, obedience rates dropped (but were still 47.5%). When the subjects did not have to administer the shocks themselves but simply sit by and take notes while someone else did, almost everyone complied (92.5%). Yet there were no clear explanations for why some individuals obeyed and some did not. Some people were chillingly obedient, others were boldly defiant, but it's not clear why. Age, religion (Catholic vs. Protestant), and political affiliation did not seem to matter. Most of the studies used male volunteers only, for some reason, but Experiment 8 used women; compared to Experiment 5 the results were pretty much identical. In the early experiments there were some indications that better educated and higher-status men were more defiant, but this did not seem to hold for all of the studies.
  7. This actually happened Again, you already knew this, but it's worth taking a moment to remember it. This really happened and it's been replicated ad nauseum; so far as I can see, no-one has succesfully criticized the basic assumptions of the paradigm (although if anyone has please let me know.) Milgram's faith in humanity seems to have been shaken by his research - his book contains case studies of individual participants which are are cynical to the point of misanthropy, even down to the level of the physical appearance and personality of the participants ("Mr Batta is a 37-year old welder...he has a rough-hewn face that conveys a conspicuous lack of alertness. His overall appearance is somewhat brutish...[during the experiment] what is remarkable is his total indifference to the learner; he hardly takes cognizance of him as a human being...the scene is brutal and depressing...at the end of the session he tells the experimenter how honored he has been to help him.") The subjects who disobeyed authority get a slightly better treatment, but not much better. Yet who can blame Milgram for this? It's worth bearing in mind also that Milgram was Jewish. His text is full of references to Nazi Germany, Hannah Arendt, the Vietnam War and the Mai Lai massacre. The hero of the book, if there is one, seems to be the young man who took part in the experiment and, as a result, decided to apply for Conscientous Objector status to avoid being sent to Vietnam. He got it.
Links: Dr Thomas Blass's StanleyMilgram.com - excellent.
Dr Blass's review paper on the Milgram paradigm.

Wednesday, December 24, 2008

Encephalon #61 is up

The 61st edition of neuroscience/psychology-based blog carnival, Encephalon, is up at Sharpbrains. I'm in it, twice, but don't let that stop you - the rest of it is pretty good...

Encephalon #61 is up

The 61st edition of neuroscience/psychology-based blog carnival, Encephalon, is up at Sharpbrains. I'm in it, twice, but don't let that stop you - the rest of it is pretty good...

Monday, December 22, 2008

John F. Kennedy, speed freak?

In his book In Sickness and In Power, the former British politician and doctor David Owen (sorry - Lord Owen) discusses the physical and mental health of various 20th century leaders.(*) The chapter on John F. Kennedy is extremely interesting. The most popular President of the century was both seriously ill and a big drug user.

Although he denied it at the time, to the point of lying, it's now known that Kennedy suffered from Addison's disease, a serious chronic condition leading to a lack of the steroid hormone cortisol, and in his case, also of thyroid hormone. As a result he required daily hormone treatments of cortisone , tri-iodothyronine and testosterone to stay alive. Kennedy also suffered from several other health problems such as chronic back pain following a World War 2 injury (his boat was rammed by a Japanese submarine and sank), and came close to death at least twice.

This is quite interesting in itself, but especially so since both cortisone and testosterone can alter mood and behaviour. In high doses, cortisone can produce mood swings, agitation and mania, and with prolonged use, depression; while testosterone... well, it's testosterone. In theory, Kennedy only needed to take enough of these hormones to achieve normal levels, but in fact, Owen says, for long periods of his Presidency he was taking much more than that, partly because doctors in the 1960s tended to use higher doses than would now be considered wise, and partly because he was being simultanously treated by a number of doctors who didn't always know what the others were doing (seriously.) Allegedly, some photos of Kennedy show symptoms of excessive cortisol levels ("Cushingoid features") such as a puffy face, although I haven't checked this. (This picture shows signs of Addison's disease - low weight and dark skin - before he was treated).

Most interestingly for drug fans, Owen says that Kennedy was a regular user of amphetamine ("speed"), which he was given by Dr Max "Dr Feelgood" Jacobson, who was essentially a high-class quack, although a very popular one. Jacobson was a methamphetamine user himself and he was eventually banned from practicing medicine in 1975. Jacobson gave Kennedy injections of amphetamine and steroids, and probabky also gave him vials of drugs to inject himself with; on at least one occasion he probably gave him methamphetamine. All of this was perfectly legal, but it was medically unnecessary, and maybe downright dangerous. Kennedy also had injections of Demerol (pethidine) for chronic back pain, a powerful painkiller which pharmacologically is rather like a cross between morphine and cocaine. Fun stuff. Jacobson, however, disappoved of this.

Owen speculates that Kennedy's medication, as well as his general health, contributed to his erratic performance during the first half of his presidency - hence the Bay of Pigs fiasco, and an embarrasingly poor form during a summit with the Soviet leader Khrushchev. Later on, when Kennedy's health situation had improved and he had cut back on the speed and steroids, he was able to handle the Cuban Missile Crisis very effectively and, probably, saved the world. A skeptic would say that Kennedy might have just learned from his mistakes of course, but Owen's theory is certainly possible, and it's worth bearing in mind when thinking about the possibility of the widespread use of "cognitive enhancers" - most of these drugs are stimulants with effects on mood and judgement. So remember - unless you want to preside over an abortive, ill-planned invasion of a small third-world country, keep away from speed.

(*)Mini-book-review: In Sickness and in Power is interesting but badly flawed; it mixes sound history with fluffy speculation seemingly at random. Would French President Mitterand have acted differently on the War in Yugoslavia if he hadn't had cancer? Would the Shah of Iran have been forced to step down earlier if he had admitted to having leukemia? Possibly - but we really don't know. Owen spends a lot of time wondering about such hypothetical questions. He has also invented a new psychiatric diagnosis, "hubris syndrome", complete with a DSM-IV style symptom checklist, with which he proceeds to diagnose people like Tony Blair and George Bush on the basis that they made bad decisions about Iraq. Fair enough, but I've have preferred to hear more about Nixon and Bush's alcoholism or about Winston Churchill's depression, which are discussed, but only briefly.

John F. Kennedy, speed freak?

In his book In Sickness and In Power, the former British politician and doctor David Owen (sorry - Lord Owen) discusses the physical and mental health of various 20th century leaders.(*) The chapter on John F. Kennedy is extremely interesting. The most popular President of the century was both seriously ill and a big drug user.

Although he denied it at the time, to the point of lying, it's now known that Kennedy suffered from Addison's disease, a serious chronic condition leading to a lack of the steroid hormone cortisol, and in his case, also of thyroid hormone. As a result he required daily hormone treatments of cortisone , tri-iodothyronine and testosterone to stay alive. Kennedy also suffered from several other health problems such as chronic back pain following a World War 2 injury (his boat was rammed by a Japanese submarine and sank), and came close to death at least twice.

This is quite interesting in itself, but especially so since both cortisone and testosterone can alter mood and behaviour. In high doses, cortisone can produce mood swings, agitation and mania, and with prolonged use, depression; while testosterone... well, it's testosterone. In theory, Kennedy only needed to take enough of these hormones to achieve normal levels, but in fact, Owen says, for long periods of his Presidency he was taking much more than that, partly because doctors in the 1960s tended to use higher doses than would now be considered wise, and partly because he was being simultanously treated by a number of doctors who didn't always know what the others were doing (seriously.) Allegedly, some photos of Kennedy show symptoms of excessive cortisol levels ("Cushingoid features") such as a puffy face, although I haven't checked this. (This picture shows signs of Addison's disease - low weight and dark skin - before he was treated).

Most interestingly for drug fans, Owen says that Kennedy was a regular user of amphetamine ("speed"), which he was given by Dr Max "Dr Feelgood" Jacobson, who was essentially a high-class quack, although a very popular one. Jacobson was a methamphetamine user himself and he was eventually banned from practicing medicine in 1975. Jacobson gave Kennedy injections of amphetamine and steroids, and probabky also gave him vials of drugs to inject himself with; on at least one occasion he probably gave him methamphetamine. All of this was perfectly legal, but it was medically unnecessary, and maybe downright dangerous. Kennedy also had injections of Demerol (pethidine) for chronic back pain, a powerful painkiller which pharmacologically is rather like a cross between morphine and cocaine. Fun stuff. Jacobson, however, disappoved of this.

Owen speculates that Kennedy's medication, as well as his general health, contributed to his erratic performance during the first half of his presidency - hence the Bay of Pigs fiasco, and an embarrasingly poor form during a summit with the Soviet leader Khrushchev. Later on, when Kennedy's health situation had improved and he had cut back on the speed and steroids, he was able to handle the Cuban Missile Crisis very effectively and, probably, saved the world. A skeptic would say that Kennedy might have just learned from his mistakes of course, but Owen's theory is certainly possible, and it's worth bearing in mind when thinking about the possibility of the widespread use of "cognitive enhancers" - most of these drugs are stimulants with effects on mood and judgement. So remember - unless you want to preside over an abortive, ill-planned invasion of a small third-world country, keep away from speed.

(*)Mini-book-review: In Sickness and in Power is interesting but badly flawed; it mixes sound history with fluffy speculation seemingly at random. Would French President Mitterand have acted differently on the War in Yugoslavia if he hadn't had cancer? Would the Shah of Iran have been forced to step down earlier if he had admitted to having leukemia? Possibly - but we really don't know. Owen spends a lot of time wondering about such hypothetical questions. He has also invented a new psychiatric diagnosis, "hubris syndrome", complete with a DSM-IV style symptom checklist, with which he proceeds to diagnose people like Tony Blair and George Bush on the basis that they made bad decisions about Iraq. Fair enough, but I've have preferred to hear more about Nixon and Bush's alcoholism or about Winston Churchill's depression, which are discussed, but only briefly.

Sunday, December 21, 2008

A Gene for Power-Line Leukemia?

Some people believe that living near high-voltage power lines raises the risk of childhood cancer. Most people are skeptical. A Chinese group have just published a paper in the journal Leukemia and Lymphoma, claiming that a genetic polymorphism in the XRCC1 gene, which has been previously linked to various cancers, raises the risk of electromagnetic field (EMF)-related leukemia. People who believe in EMF-related leukemia are happy. The Daily Mail report on this study quoting no less than three such people.

What's the real story? The authors took 123 childhood leukemia patients living near Shanghai. They took blood samples for DNA analysis and asked the parents to report on a wide range of possible environmental risk factors, not just EMF:
The mothers of the patients were interviewed at the hospital by specifically trained medical doctors using a questionnaire. Visits to the present (or previous) residential areas of 66 cases were arranged, and the actual values of magnetic field intensities were measured using an EMF detector (TriField Meter, AlphaLab, USA). Questionnaires covered information about the parents’ sociodemographic characteristics, the children’s pre and postnatal characteristics and the familial history of cancer and autoimmune diseases. The questions related to environmental exposure covered pregnancy and the period from birth to diagnosis and detailed information including: Was there a television set/refrigerator/ microwave oven in the children’s rooms? Did you regularly use insecticides at home? Did you use gardening chemicals such as, fertilisers, herbicides, insecticides, fungicides, others? Were there chemical factories/telecommunication transmitters/electric transformers/power lines around your house?
Relying on self-report like this raises the risk of recall bias, but to be honest, this doesn't seem like a major problem. Certainly there is a much bigger problem with this study (see below). The authors genotyped the children for six different SNPs (genetic variants) which have been previously implicated in cancer
The MassARRAY technology platform (Sequenom, San Diego, California, USA) was used to detect the SNPs in hMLH1 Ex8–23A4G (rs1799977), APEX1 Ex5þ5T4G (rs1130409), MGMTEx7þ 13A4G (rs2308321), XRCC1 Ex9þ16G4A (rs25489), XPD Ex10–16G4A (rs1799793) and XPD Ex23þ61 T4G (rs13181)
See the problem that's developing here? Six SNPs, who knows how many different environmental factors (the paper isn't clear, but it seems to be at least seven, see below) - that's a textbook example of multiple comparisons. Any statistical comparison has a chance of giving a positive result just by chance. If you do enough comparisons, you will find something, just by chance.

The authors do not report making an attempt to correct for this (although there are plenty of ways of doing so). They never even acknowledge the problem. They simply report on their only positive result - an association between the XRCC1 risk allele and "proximity to electrical transformers and power lines" - and relegate all the negative results to a brief summary
No significant interactions between the proximity of the electric transformers and power lines and other genotypes were observed. No significant interactions were observed between genotypes and the presence of television sets, refrigerators or microwave ovens in children’s rooms, pesticides use or the presence of chemical factories or telecommunication transmitter within 500 m of the houses.
The positive result was that out of the children with leukemia, those living within 100m of electrical transformers and power lines were more likely to carry the XRCC1 risk allele than those not living within this proximity. Those living within 50m were slightly more likely than that. Under the assumption that genotype is not correlated with environment in the general population (a reasonable assumption, and they did test this in a control sample), this indicates a G x E interaction for leukemia / lymphoma risk, with p below 0.01.

One such result from what seems like at least 42 such comparisons is not especially impressive. It's certainly not proof of an interaction between XRCC1 and EMF, it's not even "suggestive evidence", it's at best a prompt for further research. Even being generous, and assuming that they would not have reported on an association with any risk factor other than proximity to power lines, this is still 6 comparisons with different polymorphisms (more if you count the fact that children living at differing distances from power lines were tested seperately).

Postscript: I hope that I'm wrong about this. It would be great if XRCC1 raised the risk of childhood cancer, because it would mean that we could prevent some childhood cancers by keeping at-risk children away from power-lines. This post is just something I hacked together in an hour and a half on a Sunday morning, and I'm not a statistician - it would be awful if I've just spotted a serious problem with an important paper which went un-noticed by journal editors and peer reviewers. So if someone wants to disagree with me please, please do - I'll provide the PDF of the paper on request if you need it. Until then, I think that this is especially bad example of the problem of multiple comparisons and a tragic case of sloppy science which could end up having serious consequences for health, in terms of acting as a red herring distracting from more valuable research.

[BPSDB]

ResearchBlogging.orgYou Yang, Xingming Jin, Chonghuai Yan, Ying Tian, Jingyan Tang, Xiaoming Shen (2008). Case-only study of interactions between DNA repair genes (hMLH1, APEX1, MGMT, XRCC1 and XPD) and low-frequency electromagnetic fields in childhood acute leukemia Leukemia and Lymphoma, 49 (12), 2344-2350 DOI: 10.1080/10428190802441347