Trajectories of sickness absence and disability pension in young working-age adults in Sweden.

Sickness absence and disability pension (SADP) constitute a major public health concern, yet the heterogeneity in the developmental trajectories of SADP remains poorly understood. We aimed to identify trajectories of SADP in an observational cohort study of 12,721 Swedish twin individuals, born 1975-1986, who were initially invited to health screening surveys in 2005. Through linkage to nationwide registries, individuals were prospectively followed regarding annual days of SADP from 2006 to 2020. Using group-based trajectory modeling, we identified three distinct SADP trajectories in the total sample: 'high-increasing' (4%), 'low-increasing' (13%), and 'low-constant' (83%). Next, using multinomial logistic regression, we found that mental health-related factors such as neurodevelopmental conditions and common mental disorders were strongly associated with the high-increasing and low-increasing SADP trajectories. Furthermore, increasing age, female sex, low/medium educational level, and blue-collar work were found to be associated with higher odds of belonging to the high-increasing and low-increasing SADP trajectories. We did not find any effect of genetic similarity. Overall, close to every fifth individual showed rising SADP trajectories over time. Research is warranted to address the specific support needs of vulnerable young people struggling with mental health conditions, and to identify any actionable barriers to facilitate labor market integration.