AUGSBURG, Germany — Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental condition in children and teens that effects roughly five percent of minors globally. In around two-thirds of cases, the condition continues into adulthood. Now, researchers from the University of Augsburg report that ADHD is an independent risk factor for several serious mental health issues including major depression, post-traumatic stress disorder, anorexia, and suicidal behavior.
Researchers stress individuals diagnosed with ADHD should be aware of their increased risk profile in order to help ward off such developments later on. Characterized by an inability to concentrate, high energy, and impulsivity, ADHD is especially prevalent in the United States, where over six million children have been diagnosed with the disorder.
“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,” study authors write in a media release.
While ADHD has been linked in the past to numerous mood and anxiety disorders in observational studies, it’s been unclear if it has a causal association with other mental health problems. To find out, researchers used Mendelian randomization, a technique that uses genetic variants as proxies for a particular risk factor (in this case, ADHD) to gather genetic evidence supporting a specific outcome on seven common mental health problems.
Those conditions included major clinical depression, bipolar disorder, anxiety disorder, schizophrenia, PTSD, anorexia nervosa, and people making at least one suicide attempt.
To start, researchers made use of this technique to establish potential links between ADHD and the seven aforementioned disorders. That was then used to see if disorders associated with ADHD could potentially be responsible for the effects detected during the first analysis. After that, all the data from both analyses was pooled together to calculate the direct and indirect effects of ADHD.
Ultimately, the team did not see evidence of a causal link between ADHD and bipolar disorder, anxiety, or schizophrenia. However, researchers did find evidence pointing to a causal link with a heightened risk of anorexia nervosa (28%), as well as evidence that ADHD both caused (9% heightened risk) and was caused by (76% heightened risk) major clinical depression.
After researchers adjusted for the influence of major depression, a direct causal association with both attempted suicide (30% heightened risk) and PTSD (18% heightened risk) became apparent.
Still, study authors caution that while Mendelian randomization is less prone than observational studies to the influence of unmeasured factors and reverse causality (as in, ADHD could be a consequence of the various disorders studied instead of the other way round), it isn’t foolproof.
For instance, the very same gene could be associated with different traits, making it difficult to pinpoint the relevant causal effect. Moreover, only individuals of European ancestry were included, meaning these findings may not apply to other ethnicities. Nevertheless, study authors conclude that their work should encourage clinicians to be more proactive when treating ADHD patients.
The study is published in BMJ Mental Health.
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