ADHD is ‘risk factor for mental health problems’

The hyperactivity disorder usually referred to as ADHD is an independent risk factor for several common mental health issues, a new study has revealed. 

Attention-deficit/hyperactivity disorder (ADHD) is linked with major depression, post traumatic stress disorder, anorexia nervosa and suicide attempts, the findings show, prompting the researchers to recommend vigilance by health professionals in a bid to ward off these disorders later on.

“This study opens new insights into the paths between psychiatric disorders. Thus, in clinical practice, patients with ADHD should be monitored for the psychiatric disorders included in this study and preventive measures should be initiated if necessary,” they write.

ADHD is a neurodevelopmental condition in children and teens that extends into adulthood in up to around two thirds of cases. Worldwide, its prevalence is estimated to be around five per cent in children and teens, and 2.5 per cent in adults.

ADHD has been linked to mood and anxiety disorders in observational studies, but it is not known if it is causally associated with other mental ill health.

To try and find out, the researchers used Mendelian randomisation, a technique that uses genetic variants as proxies for a particular risk factor—in this case ADHD—to obtain genetic evidence in support of a particular outcome—in this study, seven common mental health issues.

These were: major clinical depression; bipolar disorder; anxiety disorder; schizophrenia; post traumatic stress disorder (PTSD); anorexia nervosa; and at least one suicide attempt.

The researchers initially used the technique to establish potential links between ADHD and the seven disorders. They then used it to see if disorders associated with ADHD could potentially be responsible for the effects detected in the first analysis. Finally, they pooled the data from both analyses to calculate the direct and indirect effects of ADHD.

There was no evidence for a causal link between ADHD and bipolar disorder, anxiety or schizophrenia, the results of the analysis showed.

But there was evidence for a causal link with a heightened risk of anorexia nervosa (28 per cent), and evidence that ADHD both caused (nine per cent heightened risk), and was caused by (76 per cent heightened risk), major clinical depression.

And after adjusting for the influence of major depression, a direct causal association with both suicide attempt (30 per cent heightened risk) and PTSD (18 per cent heightened risk) emerged.

The researchers caution that while Mendelian randomisation is less prone than observational studies to the influence of unmeasured factors and reverse causality—whereby ADHD could be a consequence of the various disorders studied rather than the other way round—it is not without its limitations.

For example, the same gene may be associated with different traits, making it difficult to pinpoint the relevant causal effect, they point out. Only people of European ancestry were included so the findings might not apply to other ethnicities.

Nevertheless, the researchers conclude that their findings should encourage clinicians to be more proactive when treating people with ADHD.