Neuroticism's prospective association with mental disorders halves after adjustment for baseline symptoms and psychiatric history, but the adjusted association hardly decays with time: a meta-analysis on 59 longitudinal/prospective studies with 443 313 participants
Background. This meta-analysis seeks to quantify the prospective association between neuroticism and the common mental disorders (CMDs, including anxiety, depression, and substance abuse) as well as thought disorders (psychosis/schizophrenia) and non-specific mental distress. Data on the degree of confounding of the prospective association of neuroticism by baseline symptoms and psychiatric history, and the rate of decay of neuroticism's effect over time, can inform theories about the structure of psychopathology and role of neuroticism, in particular the vulnerability theory. Method. This meta-analysis included 59 longitudinal/prospective studies with 443 313 participants. Results. The results showed large unadjusted prospective associations between neuroticism and symptoms/diagnosis of anxiety, depression, and non-specific mental distress (d = 0.50–0.70). Adjustment for baseline symptoms and psychiatric history reduced the associations by half (d = 0.10–0.40). Unadjusted prospective associations for substance abuse and thought disorders/symptoms were considerably weaker (d = 0.03–0.20), but were not attenuated by adjustment for baseline problems. Unadjusted prospective associations were four times larger over short (<4 year) than long (54 years) follow-up intervals, suggesting a substantial decay of the association with increasing time intervals. Adjusted effects, however, were only slightly larger over short v. long time intervals. This indicates that confounding by baseline symptoms and psychiatric history masks the long-term stability of the neuroticism vulnerability effect. Conclusion. High neuroticism indexes a risk constellation that exists prior to the development and onset of any CMD. The adjusted prospective neuroticism effect remains robust and hardly decays with time. Our results underscore the need to focus on the mechanisms underlying this prospective association.