Ben Goldacre, The Guardian, Saturday 9 October 2010

What does it mean to say that a psychological or behavioural condition has a biological cause? Over the past week more battles have been raging over ADHD, after a paper published by a group of Cardiff researchers found evidence that there is a genetic association with the condition. Their study looked for chromosomal deletions and duplications known as “copy number variants” (CNV) and found that these were present in 16% of the children with ADHD.

What many reports did not tell you – including the Guardian – is that this same pattern of CNV was also found in 8% of the children without ADHD. So that’s not a massive difference.

But more interesting were the moral and cultural interpretations heaped onto this finding, not least by the authors themselves. “Now we can say with confidence that ADHD is a genetic disease and that the brains of children with this condition develop differently to those of other children,” said Professor Anita Thapar. “We hope that these findings will help overcome the stigma associated with ADHD.”

Does the belief that such problems have a biological cause really help to reduce stigma?

In 2001, Read and Harre explored attitudes among first year undergradute psychology students, with questionnaires designed to probe belief about the causes of mental health problems, and responses on 6-point scales to statements like “I would be less likely to become romantically involved with someone if I knew they had spent time in a psychiatric hospital”. People who believed more in a biological or genetic cause were more likely to believe that people with mental health problems are unpredictable and dangerous, more likely to fear them, and more likely to avoid interacting with them. An earlier study in 1999 by Read and Law had similar results.

In 2002 Walker and Read showed young adults a video portraying a man with psychotic symptoms, such as hallucinations and delusions, then gave them either biogenetic or psychosocial explanations. Yet again, the “medical model” approach significantly increased perceptions of dangerousness and unpredictability.

In 2004 Dietrich and colleagues conducted a huge series of structured interviews with three representative population samples in Germany, Russia and Mongolia. Endorsing biological factors as the root cause for schizophrenia was associated with a greater desire for social distance.

And lastly, more compelling than any individual study, a review of the literature to date in 2006 found that overall, biogenetic causal theories, and labelling something as an “illness”, are both positively related to perceptions of dangerousness and unpredictability, and to fear and desire for social distance. They identified 19 studies addressing the question. 18 found that belief in a genetic or biological cause was associated with more negative attitudes to people with mental health problems. Just one found the opposite, that belief in a genetic or biological cause was associated with more positive attitudes.

These findings are at odds with everything that many people who campaign against stigma have assumed for many years, but they’re not entirely nonsensical. As Jo Phelan explains in her paper “Genetic bases of mental illness – a cure for stigma?”, a story about genetic causes may lead to people being conceived of as “defective” or “physically distinct”. It can create an “associative stigma” for the whole family, who in turn receive new labels such as “at risk” or “carrier”. What’s more, this stigma may persist long after the ADHD symptoms have receded in adulthood: perhaps a partner will wonder: “do I really want to risk having a child with this person, given their genetic predisposition?”

Perhaps it will go further than that: your children, before they even begin to show any signs of inattentiveness or hyperactivity, will experience a kind of anticipatory stigma. Do they have this condition, just like their father? “It’s genetic you know.” Perhaps the threshold for attaining a diagnosis of ADHD will be lower for your children: it’s a condition, like many others, after all, with a notably flexible diagnostic boundary.

Blaming parents is clearly vile. But before reading this research I think I also assumed, unthinkingly, like many people, that a “biological cause” story about mental health problems was inherently valuable for combatting stigma. Now I’m not so sure. People who want to combat prejudice may need to challenge their own prejudices too.