Scientists have discovered that neurodevelopmental disorder attention-deficit/hyperactivity disorder (ADHD), which is largely inherited, directly increases the risk of sufferers also developing major depression, post-traumatic stress, anorexia nervosa and attempting suicide. The findings, which came out of a massive meta-analysis study across many datasets breaks new ground in understanding ADHD and its comorbidities.
In an effort to reduce the prevalence of confounding issues and reverse causation, scientists from the University of Augsburg in Germany used a two-sample Mendelian randomization analysis, looking at genetic variants to determine direct comorbidity risks. The researchers used this method to establish potential links between ADHD and seven illnesses: major clinical depression, bipolar disorder, anxiety disorder, schizophrenia, post traumatic stress disorder (PTSD), anorexia nervosa and at least one suicide attempt.
“We used a range of datasets to obtain the best possible evidence,” noted the researchers. “We used genome-wide association studies (GWASs) from the iPSYCH project and the Psychiatric Genomics Consortium (PGC) in the main analyses.”
Two analyses were conducted to calculate direct and indirect effects of ADHD, and the results were surprising. The researchers found no causal link between ADHD and bipolar disorder, schizophrenia or anxiety, although around three in 10 children diagnosed with the neurodevelopment disorder have anxiety as a comorbidity.
However, they did find causal links and an increased risk factor for anorexia nervosa (28%), and evidence that ADHD both caused (9% heightened risk), and was caused by (76% heightened risk), depression. Adjusting the results to account for the influence of depression on other conditions, the researchers found a direct causal association with suicide attempt (30% heightened risk) and PTSD (18%).
The scientists point out that there are limitations of their study due to the complexity of these conditions. For instance, the same gene could be associated with different traits, making it difficult to pinpoint causal effect. However, there are common through lines, such as genetic impulsivity found in both ADHD and those who have attempted suicide, and emotional dysregulation, which is also a key factor in anorexia nervosa and PTSD.
Worldwide, around 5.3% of children and teens and 2.5% of adults have ADHD, with the numbers likely higher due to emerging adult diagnoses. Once mainly seen as a disorder marked by behavioral problems in predominantly male children, it’s now better understood to be a neurological dysfunction that impedes executive function, emotional regulation and motivation.
In 2020, it was estimated that more than 366 million adults worldwide had ADHD. There is no cure; just treatment to manage symptoms that can greatly interfere with work and personal lives.
While thought of to be largely genetic, accounting for around 70%-80% of ADHD cases, there’s not a single gene responsible for the condition, and scientists are still working to understand how societal and other factors contribute.
ADHD has recently been linked to a smorgasbord of non-mental diseases. This study not only serves as an early warning system for mental health comorbidities, but can guide clinicians in better understanding the relationships between disorders and how best to treat them.
”This study opens new insights into the paths between psychiatric disorders,” said the authors. “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.”
The research was published in BMJ Mental Health.
Source: University of Augsburg, via EurekAlert
