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21-01-2023 | Original Paper

Military service and risk of subsequent drug use disorders among Swedish men

Authors: Alexis C. Edwards, Henrik Ohlsson, Peter B. Barr, Jan Sundquist, Kenneth S. Kendler, Kristina Sundquist

Published in: Social Psychiatry and Psychiatric Epidemiology | Issue 7/2023

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Abstract

Purpose

Environmental factors contribute substantially to risk for drug use disorders (DUD). The current study applies multiple methods to empirically test whether military service is associated with subsequent DUD, as previous findings are inconsistent.

Methods

Longitudinal Swedish national registry data on a cohort of male conscripts born 1972–1987 (maximum N = 485,900) were used to test the association between military service and subsequent registration for DUD. Cox proportional hazard models were used in preliminary analyses, followed by three methods that enable causal inference: propensity score models, co-relative models, and instrumental variable analysis.

Results

Across all methods, military service was causally associated with lower risk of DUD. Hazard ratios ranged from HR = 0.43 (95% confidence intervals [CI] 0.37; 0.50) in the instrumental variable analysis to 0.77 (0.75; 0.79) in the multivariate propensity score matching analysis. This effect diminished across time. In the model including a propensity score, HRs remained below 1 across the observation period, while confidence intervals included 1 after ~ 11 years in the co-relative analysis and after ~ 21 years in the instrumental variable analysis.

Conclusions

In this cohort of Swedish men, complementary methods indicate that military service conferred substantial but time-limited protection against subsequent DUD. The observed effect could be due to reduced opportunity for substance use during service, social cohesion experienced during and after service, and/or socioeconomic advantages among veterans. Additional research is necessary to clarify these protective mechanisms and determine how other environmental contexts can provide similar benefits.
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Metadata
Title
Military service and risk of subsequent drug use disorders among Swedish men
Authors
Alexis C. Edwards
Henrik Ohlsson
Peter B. Barr
Jan Sundquist
Kenneth S. Kendler
Kristina Sundquist
Publication date
21-01-2023
Publisher
Springer Berlin Heidelberg
Published in
Social Psychiatry and Psychiatric Epidemiology / Issue 7/2023
Print ISSN: 0933-7954
Electronic ISSN: 1433-9285
DOI
https://doi.org/10.1007/s00127-023-02426-y