Fig. 1

Study flow diagram. The SNPs from GWAS applied as instrumental variables (IVs) were related to exposures (assumption 1). Dash lines with a cross means that IVs must not be associated with confounders (assumption 2) and IVs affect the risk of outcome directly by exposure and not through other alternative pathways (assumption 3). The dash lines indicate irrelevance, and the solid lines indicate relevance. PDE phosphodiesterase, AD Alzheimer disease, ADHD attention-deficit/hyperactivity disorder, AN anorexia nervosa, ASD autism spectrum disorder, BD bipolar disorder, MDD major depressive disorder, OCD obsessive–compulsive disorder, SCZ schizophrenia, TS Tourette syndrome, IVW inverse-variance weighted, WM weighted-median, MR Mendelian randomization, MR-PRESSO MR pleiotropy residual sum and outlier