@article {van den Broek168690, author = {Nina van den Broek and Jorien L. Treur and Junilla K. Larsen and Maaike Verhagen and Karin J. H. Verweij and Jacqueline M. Vink}, title = {Causal Associations Between Body Mass Index and Mental Health: A Mendelian Randomization Study}, elocation-id = {168690}, year = {2017}, doi = {10.1101/168690}, publisher = {Cold Spring Harbor Laboratory}, abstract = {Background Body Mass Index (BMI) is negatively correlated with subjective well-being and positively correlated with depressive symptoms. Whether these associations reflect causal effects or confounding is unclear.Methods We examined causal effects between BMI and subjective well-being/depressive symptoms with bi-directional, two-sample Mendelian randomization using summary-level data from large genome-wide association studies. Genetic variants robustly related to the exposure variable acted as instrumental variable (two thresholds were used; p\<5e-08 and p\<1e-05). These {\textquoteleft}instruments{\textquoteright} were then associated with the outcome variable. Pleiotropy was corrected for by two sensitivity analyses.Results Substantial evidence was found for a causal effect of BMI on mental health, such that a higher BMI decreased subjective well-being and increased depressive symptoms. No consistent evidence was found for causality in the other direction.Conclusions This study provides support for a higher BMI causing poorer mental health. Further research should corroborate these findings and consider non-linear effects and sex differences.}, URL = {https://www.biorxiv.org/content/early/2017/07/26/168690}, eprint = {https://www.biorxiv.org/content/early/2017/07/26/168690.full.pdf}, journal = {bioRxiv} }