The weight of weights: Causal impact of overweight on major depressive disorder and its disparate association with suicide attempts in over 450,000 individuals of European ancestry (AM-SRNMA 003).

AIM: Some studies and societal discussions have suggested a potential link between overweight and a higher risk of mental disorders and suicidal ideation. However, the causal relationships between these factors remain unclear. This study aims to assess the bidirectional causal associations between overweight and mental disorders, including suicidal attempts.

METHOD: We conducted a Two-Sample Mendelian Randomization study utilizing data from over 450,000 individuals of European ancestry sourced from a comprehensive Genome-Wide Association Study database. We chose single-nucleotide polymorphisms as instrumental variables.

RESULTS: Our analyses consistently supported a unidirectional causal association of overweight with the increased risk of major depressive disorder (MDD, β = 0.152, se = 0.069, P = 0.027), bipolar affective disorders (BD, β = 0.197, se = 0.092, P = 0.033), and attention-deficit / hyperactivity disorder (ADHD, β = 0.308, se = 0.080, P = 1.366 × 10-4). We observed no significant causal relationships for the exposure of overweight to anxiety disorder (AD), manic episode (MA), panic disorder (PD), schizophrenia (SZ), substance use disorder (SUD), autism spectrum disorder (ASD), ever attempted suicide, recent thoughts of suicide or self-harm, and suicide or other intentional self-harm events.

CONCLUSION: This study has provided evidence for the causal relationship between overweight and MDD, BD, ADHD, with no observed relationship between overweight and AD, MA, PD, SZ, SUD, ASD, ever attempted suicide, recent thoughts of suicide or self-harm, and suicide or other intentional self-harm events.