Prevalence of addictions differs significantly across countries, largely because conscription systems vary in how they screen and exempt recruits. In many armies, the use of “hard” drugs can exempt someone from forced service, allowing addicts to free-ride on collective security while abstainers bear the burden. This is of course an arrangement that can create perverse incentives for draft avoidance (“Drugs bar you from service? Then pass the heroin needle.”). Many countries, for instance in parts of South America where drug use is widespread, are therefore pressured to limit such exemptions and conscript more broadly. By contrast, many European systems try to purge at least the more serious drug users from the ranks, though scandals still occur: in Finland for instance, a joint police-Defence Forces raid in 2014 at the Pori Brigade identified a cluster of 13 conscripts, who were drug addicts.

Conscription can impact addictions in two disparate ways. For the worst and most avid addicts military training is so time-consuming and demanding that it limits opportunities to engage in harmful behaviour. Alternatively, one can posit a pattern in which mandatory military service predisposes to the experience of isolation, boredom and loneliness. The lone conscript is far away from home and his social network, forced to endure a monotonous and meaningless service. Harmful practices become the only escape from his condition.

Unfortunately, the latter case tends to dominate. Most dangerous behaviours and addictions are not time-intensive enough to be prevented by conscription: it takes only a couple of hours per day to develop a pattern of heavy alcohol consumption. If the state conscripts a heroin user who spends his days taking heroin, conscription may reduce his drug use simply by taking away the time and opportunity for that habit. However, if the state puts an occasional smoker into army barracks with a couple of hours per day of leisure time, who is highly constricted by his physical circumstances, he is likely to relish in his toxic habit. 

Conscription in that sense is a force bringing everyone together to the lowest common denominator. It may help rare cases reduce their intake of addictives. It will however deliver overwhelming harm to the vast majority. Draftees will pick up habits they would never seek in civilian life. And then you just need to wait for army ranks to foster the adaptation of similar harmful habits through peer pressure. A draftee will leave the confines of military barracks, but the habits entrenched in his psyche will remain with him and damage his civilian life.