Genetic Predisposition and Smoking Linked to Mental Health Disorders

A recent study published in the Acta Psychiatrica Scandinavica shed new light on the complex relationship between cigarette smoking, genetic predisposition, and mental health disorders. This research, based on an event history framework, offers fresh insights into the evolution of mental disorders in individuals' lives. The study, involving 337,140 participants of white British ancestry, aimed to estimate the contributions of genetic predisposition and smoking habits to hospitalizations for major depression, bipolar disorder, and schizophrenia.

Researchers calculated polygenic risk scores (PRS) for three key variables: ever smoking, pack-years of smoking as a proportion of adult life, and neuroticism. These PRS values, alongside self-reported smoking status (never, former, and present smoker), were entered into survival models to assess their impact on the risk of hospitalization for mental disorders.

The study unveiled that genetic predispositions significantly affect the risk of hospitalization for mental disorders. Specifically, the heritabilities (h2) for pack-years, ever smoking, and neuroticism were estimated at 23%, 5.7%, and 5.7%, respectively.

Remarkably, PRS for both pack-years and neuroticism were associated with a higher risk of mental health hospitalization across all smoking status groups. Even more striking were the findings related to smoking status itself. The hazard for mental health hospitalization was significantly higher in both former (HR: 1.50, CI: 1.35–1.67) and current smokers (HR: 2.58, CI: 2.97–4.31) compared to those who had never smoked, even after adjusting for potential confounders.

This study has important implications for mental health prevention strategies. Given that genetic predispositions to smoking and neuroticism are established at conception and that smoking habits typically start in adolescence, the research suggests a critical window of opportunity for intervention.

These findings underscore the importance of preventing smoking initiation in adolescents as a potential means to mitigate the development of mental disorders later in life. Such preventive measures, when targeted at this vulnerable age group, may have a substantial impact on reducing the burden of mental health hospitalizations. While this study provides valuable insights, further research is needed to explore the mechanisms through which genetic predispositions and smoking interact to influence mental health outcomes. 

Reference:

Balbuena, L., Peters, E., & Speed, D. (2023). Using polygenic risk scores to investigate the evolution of smoking and mental health outcomes in UK biobank participants. In Acta Psychiatrica Scandinavica. Wiley. https://doi.org/10.1111/acps.13601