Both mental illnesses and intellectual disabilities can make it difficult for someone to function in society. But they're distinct groups of problems, and the treatments you'd use for one simply won't be effective for the other.

A new study suggests that doctors in the UK haven't kept those facts in mind when writing prescriptions. The study found that antipsychotics were frequently being prescribed to those with intellectual disabilities, even if the patients had never been diagnosed with symptoms of a mental illness. Evidence suggests that this may have been done simply to deal with behavioral problems.

Intellectual disabilities interfere with a person's ability to process information. While this would obviously interfere with academic achievement, it also limits a person's ability to develop social and practical skills. As a result, you might expect some behavioral issues when these individuals interact with society at large.

The authors of the new paper, based at the University College London, suspected that these issues might get treated inappropriately—with a focus on suppressing them, rather than handling the underlying cause. So they took advantage of the UK's national health system, searching its records for people who had been diagnosed as having intellectual disabilities. They came up with more than 33,000 adults.

Among those, more than 9,000 had been treated with antipsychotics, potent drugs that are intended for people who are suffering from delusions or hallucinations. But checking their medical records, the team found relatively few diagnoses of severe mental illness—over 70 percent of those who received the drugs had no indications in their records that they had any of the symptoms they're meant to treat.

The authors then went through the records looking for indications of what they termed "challenging behavior," defined as "aggression, self injury, stereotypic behaviour, agitation, disruptive or destructive acts, withdrawn behaviour, arson, and sexual misconduct." These behaviors were three times more common in those with severe intellectual disabilities compared to those diagnosed as having mild ones. Those with autism were twice as likely to display them than people with Down syndrome.

But they weren't entirely common; only 25 percent of the full population had an indication of challenging behavior. But those with challenging behavior ended up prescribed the antipsychotics twice as often as the rest of the group.

The authors' overall conclusions are pretty straightforward. "The proportion of people with intellectual disability who have been treated with psychotropic drugs far exceeds the proportion with recorded mental illness," they write. "Antipsychotics are often prescribed to people without recorded severe mental illness but who have a record of challenging behaviour."

Why might this be the case? The results suggest that, when confronted with this behavior, many clinicians are simply attempting to stop it, rather than treat it, and the medications are effective at doing so. (Or at least have the reputation for being effective.) But there are problems with this approach, as antipsychotics are powerful drugs with significant side effects. They can easily take someone who has difficulty coping with society and add to their difficulty.

It could be that these drugs are actually effective for handling this behavior; the problem is that we simply don't have evidence either way. And, until we have that information, it could be that we're taking a risk with a vulnerable population.

Open Access at BMJ, 2015. DOI: 10.1136/bmj.h4326 (About DOIs).

Listing image by Flickr user Laura Gilmore