Violent crime among Swedish military veterans after deployment to Afghanistan: a population-based matched cohort study.

Objective: To investigate the incidence of violent crime conviction among Swedish military veterans after deployment to Afghanistan versus non-deployed comparators. The main outcome was first conviction of a violent crime, retrieved from the Swedish National Council for Crime Prevention Register until December 31, 2013.

Methods: This was a cohort study of military veterans identified through personnel registers regarding deployment to Afghanistan between 2002 and 2013 (n = 5894). To each military veteran, up to five non-deployed comparators identified via the Military Service Conscription Register were matched by age, sex, conscription year, cognitive ability, psychological assessment, self-reported mental health, body mass index, antidepressants/anxiolytics prescriptions and self-harm (fully matched comparators; n = 28 895). Multivariable adjustment was made for substance abuse and previous health care visits with psychiatric diagnoses. An additional comparator group matched only for age, sex and conscription year was also used (age-sex-matched comparators; n = 29 410).

Results: During 21 898 person-years of follow-up (median = 3.6 years) there were 26 events among deployed military veterans compared with 98 in non-deployed fully matched comparators [12 vs 9 per 10 000 person-years, adjusted hazard ratio (aHR) 1.36; 95% confidence interval (CI) 0.88-2.10]. Among non-deployed age-sex-matched comparators there were 170 violent crime convictions (16 per 10 000 person-years; aHR 0.85; 95% CI 0.56-1.29). Factors associated with greater risk of violent crime convictions were younger age, lower scores on cognitive ability tests and psychological assessment, and convictions preceding deployment.

Conclusion: The violent crime conviction rate after returning from military deployment to Afghanistan was not different compared with non-deployed comparators in individuals without history of violent crime convictions.