Is there a causal relationship between executive function and liability to mental health and substance use? A Mendelian randomization approach

Poorer performance in tasks testing executive function (EF) is associated with a range of psychopathologies such as schizophrenia, major depressive disorder (MDD) and anxiety, as well as smoking and alcohol consumption. We used two-sample bidirectional Mendelian randomization to examine whether these may reflect causal relationships and the direction of causation. We used genome-wide association study summary data (N = 17 310 to 848 460) for a common EF factor score (cEF), schizophrenia, MDD, anxiety, smoking initiation, alcohol consumption, alcohol dependence and cannabis use disorder (CUD). We found evidence of increased cEF on reduced schizophrenia liability (OR = 0.10; CI: 0.05 to 0.19; p-value = 3.43 × 10−12), MDD liability (OR = 0.52; CI: 0.38 to 0.72; p-value = 5.23 × 10−05), drinks per week (β = –0.06; CI: –0.10 to −0.02; p-value = 0.003) and CUD liability (OR = 0.27; CI: 0.12 to 0.61; p-value = 1.58 × 10−03). We also found evidence of increased schizophrenia liability (β = −0.04; CI: −0.04 to −0.03; p-value = 3.25 × 10−27) and smoking initiation on decreased cEF (β = −0.06; CI: −0.09 to −0.03; p-value = 6.11 × 10−05). Our results indicate potential causal relationships between cEF and mental health and substance use. Further studies are required to improve our understanding of the underlying mechanisms of these effects, but our results suggest that EF may be a promising intervention target for mental health and substance use.