Importance: Mental health problems in early life are associated with labor market marginalization, especially in youths with persistent internalizing and externalizing problems. However, previous research has not adjusted for familial (genetic and shared environmental) factors.
Objective: To examine associations of early-life internalizing and externalizing problems with adulthood unemployment and work disability, adjusting for familial factors.
Design, setting, and participants: This population-based prospective cohort study included Swedish twins who were born in 1985-1986 and surveyed at 4 consecutive waves across childhood and adolescence until 2005. Through linkage to nationwide registries, participants were followed up from 2006 to 2018. Data analyses were conducted between September 2022 and April 2023.
Exposures: Internalizing and externalizing problems, assessed with the Child Behavior Checklist. Participants were differentiated regarding duration of internalizing and externalizing problems (persistent, episodic, and noncases).
Main outcomes and measures: Unemployment (180 days or more of being unemployed) and work disability (60 days or more of being sickness absent or disability pensioned) during follow-up. Cox proportional hazards regression models were calculated to obtain cause-specific hazard ratios (HRs) with 95% CIs in the whole cohort and exposure-discordant twin pairs.
Results: Of 2845 participants, 1464 (51.5%) were female. Incident unemployment was experienced by 944 (33.2%) and incident work disability by 522 (18.3%) participants. Compared with noncases, persistent internalizing problems were associated with unemployment (HR, 1.56; 95% CI, 1.27-1.92) and work disability (HR, 2.32; 95% CI, 1.80-2.99). Similarly, compared with noncases, persistent externalizing problems were associated with unemployment (HR, 1.87; 95% CI, 1.55-2.26) and work disability (HR, 2.38; 95% CI, 1.87-3.03). Persistent cases had overall higher risks of adverse outcomes than episodic cases. After adjustment for familial factors, associations with unemployment were no longer statistically significant, whereas associations with work disability remained or were only slightly reduced.
Conclusions and relevance: In this cohort study of young Swedish twins, familial factors explained the associations between early-life persistent internalizing and externalizing problems and unemployment; such factors were comparatively less important for the association with work disability. This suggests nonshared environmental factors may be important for the risk of future work disability among young individuals with persistent internalizing and externalizing problems.