Is serving in the armed forces associated with tobacco or cannabis initiation? A study of onset sequences before and after joining the French armed forces

• Substance initiation among military occurs mostly before entering the services.
• Military seem to be likelier than civilians to initiate cannabis before tobacco.
• This observation could traduce more sensation-seeking behaviours.
• We did not found evidence to confirm a military social inducement effect.

The aim of this study was to evaluate whether joining the military could constitute a predictor of subsequent tobacco or cannabis use. Data from four cross-sectional surveys conducted between 2005 and 2009 in the French armed forces were used to constitute a retrospective cohort (n = 4208). A Markov multi-state model was fitted, estimating the probabilities at 1 year for all possible pathways between entry into the military profession, tobacco initiation and cannabis initiation. The model was adjusted for current substance use status. Substance initiation appeared to mainly occur before entering the services than during the service period (3.0 times greater likelihood for tobacco and 2.5 times greater likelihood for cannabis). Probabilities of primo-initiation (i.e. starting with that substance) before joining the services were similar for tobacco (3.6% at one year) and cannabis (3.5%). When the study was restrained to current users, although differences were not statistically significant, probabilities of substance primo-initiation during the service period seemed to be greater than before. While the substance use itinerary in the French general population most often begins by tobacco, military seem to have a higher propensity to cannabis primo-initiation, which could traduce more sensation-seeking behaviors. If certain results in our study could also evoke a propensity to substance initiation during the service period, we did not find evidence to verify the hypothesis of a military social inducing effect. Further research is needed to identify behavioral characteristics which could explain increased use during the service period.