Genes

People with ADHD often have comorbid conditions like substance abuse, alcoholism and binge eating. According to some new research from a doctoral candidate at Linköping University in Sweden, a lot of the blame for this unholy alliance between ADHD and other conditions seems to lie in the genes.

A few days ago, Andrea Johansson Capusan defended her doctoral thesis, which looked at the role of genes and environment in ADHD and these other conditions. Capusan’s research included several striking findings.

First, it demonstrated a strong correlation between adult ADHD and illicit drug use, alcohol dependence, alcohol abuse and habitual nicotine use.

But it didn’t stop there. It went on to ask the question: why does ADHD seem to be associated with these other conditions?

Capusan addressed this question with a series of twin studies including thousands of participants from the Swedish Twin Registry. With these kinds of studies, researchers can compare identical and fraternal twins to learn more about the effects of genes and environment. In this case, Capusan was interested in how much of the overlap between ADHD and the comorbid conditions could be explained by each factor.

One study Capusan did looked specifically at the relationship between ADHD and alcoholism. It turned out that 64 percent of the overlap between the two came down to common genetic factors.

When it came to ADHD and binge eating, the results were even more dramatic. Ninety-one percent of the link between the two was hereditary!

Although additional research is needed to paint a more complete picture of how ADHD relates to alcoholism, substance abuse and binge eating, these findings give a strong clue that a lot of the link between ADHD and these comorbid conditions has to do with genes.

This is also research with real clinical implications. Capusan explained that “When treating adults who come with dependency disorder or substance-abuse behaviour, it’s important to remember that ADHD is very common in these patients. And conversely–it’s important to treat ADHD early in order to prevent alcohol dependence and binge eating later in life.”