The role of job strain in understanding midlife common mental disorder: a national birth cohort study.

BACKGROUND: Long-standing concerns exist about reverse causation and residual confounding in the prospective association between job strain and risk of future common mental disorders. We aimed to address these concerns through analysis of data collected in the UK National Child Development Study, a large British cohort study.

METHODS: Data from the National Child Development Study (n=6870) were analysed by use of multivariate logistic regression to investigate the prospective association between job strain variables at age 45 years and risk of future common mental disorders at age 50 years, controlling for lifetime psychiatric history and a range of other possible confounding variables across the lifecourse. Population attributable fractions were calculated to estimate the public health effect of job strain on midlife mental health.

FINDINGS: In the final model, adjusted for all measured confounders, high job demands (odds ratio 1·70, 95% CI 1·25-2·32; p=0·0008), low job control (1·89, 1·29-2·77; p=0·0010), and high job strain (2·22, 1·59-3·09; p<0·0001) remained significant independent predictors of future onset of common mental disorder. If causality is assumed, our findings suggest that 14% of new cases of common mental disorder could have been prevented through elimination of high job strain (population attributable fraction 0·14, 0·06-0·20).

INTERPRETATION: High job strain appears to independently affect the risk of future common mental disorders in midlife. These findings suggest that modifiable work-related risk factors might be an important target in efforts to reduce the prevalence of common mental disorders.

FUNDING: iCare Foundation and Mental Health Branch, NSW Health.