Christa Meisinger, M.D., M.P.H., and Dennis Freuer, from the University of Augsburg in Germany, examined the direct and indirect causal links between ADHD and seven common mental disorders. To identify psychiatric disorders causally related to ADHD, a two-sample network Mendelian randomization analysis was performed. Total and direct effects were estimated, and the robustness of results was ensured with a range of pleiotropy-robust methods, an iterative approach identifying and excluding outliers, and use of up to two genome-wide association studies per outcome to replicate results and calculate pooled estimates. A range of datasets were used to obtain the best possible evidence.
The researchers found an independent association for genetic liability to ADHD with the risk for anorexia nervosa (odds ratio, 1.28). A bidirectional association was identified with major depressive disorder, with odds ratios of 1.09 and 1.76 in the forward and reverse directions, respectively. A direct association with both suicide attempt and posttraumatic stress disorder was seen after adjustment for major depressive disorder (odds ratios, 1.30 and 1.18, respectively). No evidence of a relationship with anxiety, bipolar disorder, or schizophrenia was seen.
"The present findings are important for clinicians treating patients with ADHD because they provide a guide as to the mental comorbidities on which to focus preventively and therapeutically during the course of the disease," the authors write.
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