The research published in the open access journal BMJ Mental Health reveals that attention-deficit/hyperactivity disorder (ADHD) is a significant risk factor for various mental health issues. The study found that ADHD is linked to major depression, post traumatic stress disorder (PTSD), anorexia nervosa, and suicide attempts. As a result, the researchers recommend that health professionals remain vigilant to prevent these disorders from developing later on.
ADHD is a neurodevelopmental condition that typically begins in childhood and continues into adulthood in around two-thirds of cases. Its prevalence is estimated to be around 5% in children and teens and 2.5% in adults worldwide.
Although observational studies have already linked ADHD to mood and anxiety disorders, it is not known if there is a causal association with other mental health problems. To investigate this, the researchers used a technique called Mendelian randomisation. By using genetic variants as proxies for ADHD, they gathered genetic evidence to support associations with seven common mental health issues, including major clinical depression, bipolar disorder, anxiety disorder, schizophrenia, PTSD, anorexia nervosa, and suicide attempts.
The initial analysis allowed the researchers to establish potential links between ADHD and these disorders. They then examined if the disorders associated with ADHD could be responsible for the effects observed in the first analysis. Finally, they combined the data from both analyses to calculate the direct and indirect effects of ADHD.
The results of the analysis showed no evidence of a causal link between ADHD and bipolar disorder, anxiety, or schizophrenia. However, there was evidence of a causal link with a heightened risk of anorexia nervosa and major clinical depression. ADHD was found to both cause and be caused by major clinical depression. Moreover, a direct causal association also emerged between ADHD and suicide attempts, as well as PTSD, after accounting for the influence of major depression.
The researchers acknowledge that Mendelian randomisation has its limitations but note that it is less susceptible to unmeasured factors and reverse causality compared to observational studies. They mention that the same gene might be associated with different traits, making it challenging to identify the relevant causal effect. It should be noted that the study only included individuals of European ancestry, so the findings may not apply to other ethnicities.
Nonetheless, the researchers believe that their findings should encourage clinicians to take a proactive approach when treating individuals with ADHD. They recommend monitoring patients with ADHD for the mental disorders examined in the study and implementing preventive measures if necessary.