The Indigestible

It’s all over the wire today that there are quantitative differences to be found in brain development between kids who have been diagnosed as ADHD and those who have not.

A longitudinal study by NIMH and McGill University seems to show that nearly 225 kids aged 6 to 16 have less dense neuronal structure if they’ve also been diagnosed as having ADHD, while the same number of kids who lack the diagnosis appear to have undergone normal brain development.

While on the surface this appears to be a positive correlation between ADHD and unusual brain development, there’s a serious flaw in the study which I found admitted to in only one piece mentioning it:

About 80 percent of those with attention problems were taking or had taken stimulant drugs, and the researchers did not know the effect of the medications on brain development.

In other words we still don’t know if putting ADHD-diagnosed kids on drugs is a good idea, or if it might even worsen the problem. There was no unmedicated control group, and because of the diagnoses, there wasn’t even a possibility of a double-blind comparison. There was no indication of normalization of other factors (such as diet, amount of physical activity, time spent reading versus watching TV or playing video games, etc.) and the researchers themselves have said that it took years for the development differences to even be noticed:

Doctors cannot diagnose attention deficit or any other psychiatric disorder with imaging technology, in part because brains vary so much that a single series of images can seldom reveal who has a disorder. The new findings suggest that searching for a clear abnormality or flaw is the wrong approach, at least for attention problems.

So what we appear to have here is a correlation, of sorts, but absolutely no indication of causative factors, and no significant confidence in drawing a conclusion about the efficacy — or desirability — of medicines in treating ADHD diagnosis.