Educational attainment and mental health outcomes: A within-sibship Mendelian randomization study.

Background: Observational studies indicate that higher educational attainment (EA) is associated with a lower risk of many mental health conditions (MHC). We assessed to what extent this association is influenced by genetic nurture and demographic factors (i.e., assortative mating and population structure).

Methods: We conducted a within-sibship Mendelian randomization (MR) study. The sample consisted of 61 880 siblings (27 507 sibships) from the Trøndelag Health Study-HUNT (Norway) and UK Biobank (United Kingdom). MHC outcomes included symptom scores for anxiety, depression, and neuroticism, measured using the Hospital Anxiety and Depression Scale, the 7-item Generalized Anxiety Disorder Scale, the 9-item Patient Health Questionnaire, and the Eysenck Personality Questionnaire, along with self-reported psychotropic medication use.

Results: One standard deviation (SD) increase in liability to EA was associated with lower anxiety (-0.20 SD [95% CI: -0.26, -0.14]), depression (-0.11 SD [-0.43, -0.22]), and neuroticism scores (-0.30 SD [-0.53, -0.06]), as well as lower odds of psychotropic medication use (OR: 0.60 [0.52, 0.69]). Within-sibship MR estimates remained consistent with population-based estimates: anxiety (-0.17 SD [-0.33, -0.00]); depression (-0.18 SD [-1.26, 0.89]); neuroticism (-0.29 SD [-0.43, -0.15]); psychotropic medication use (OR, 0.52 [0.34, 0.82]).

Conclusions: Higher EA or genetic liability to education reduces symptoms of anxiety, neuroticism, and psychotropic medication use. These mental health benefits do not seem to be explained by EA-linked genetic nurture or demographic factors. Regarding depression, results were less conclusive due to imprecise estimates, though beneficial effects of genetic liability to higher EA are possible and warrant further investigation.