Trajectories of NEET (Not in Education, Employment, and Training) in emerging adulthood, and later drug use disorder - a national cohort study.

Background: Being not in education, employment, or training (NEET) has been associated with poor health outcomes. This study aimed to investigate the association between NEET during emerging adulthood and later drug use disorder (DUD) among males and females.

Method: A national cohort comprising 383,116 Swedish males and 362,002 females born between 1984 and 1990. NEET exposure was assessed annually between the ages 17 and 24 years, and follow-up for DUD between ages 25-33. Trajectories of NEET were estimated using group-based trajectory analysis. Cox regression analysis was used to estimate hazard ratios (HR) of DUD. Sibling-comparison model was performed to account for potential shared genetic and environmental factors.

Results: Four trajectories of NEET were identified: "constant low", "transient peak", "late increase", and "constant high". Compared with the "constant low", all other trajectories were associated with increased HRs of DUD. HR was highest among males and females in the "late increase trajectory"; HR = 4.10 (3.79-4.44, 95% CI) and HR = 3.73 (3.29-4.24, 95% CI), after adjusting for domicile, origin, birth year, psychiatric diagnoses, and parental psychiatric diagnoses. This association was reduced to about a twofold increased risk in the sibling comparison analysis.

Conclusion: Being NEET during emerging adulthood was associated with later DUD for both males and females. Neither origin, psychiatric diagnoses, parental psychiatric diagnoses, nor shared familial factors did fully explain the association. Males and females belonging to the late increase NEET trajectory had about a twofold increased risk of DUD.