Background: Mental ill-health is common among prisons inmates. More than half of inmates in Swedish prisons suffer from different psychiatric problems that untreated can contribute to aggressive behaviors, including self-directed aggressive behaviors such as self-harm, suicide attempt or completed suicide. Evidence shows that participation in yoga exercise may improve mental health in the general but even in prison inmates population. The effect of yoga on self-directed aggressive behavior in prison inmates population has not yet been specifically studied, according to our knowledge.

Aim: To examine the self-reported prevalence of psychiatric diagnoses by gender among prison inmates, and to study the effect of 10 weeks yoga on the prevalence and severity of self-directed aggression in this population.

Method/Study population: From nine prisons in Sweden, 211 inmates participated voluntarily in the 10 weeks of study. They were randomized into two groups, one yoga group in which inmates participated in 90 minutes of hatha yoga once every week and a control group including those who were placed into a waiting list for yoga and asked to participate in 90 minutes of physical activity of free choice, once a week during the study.

Results: Major depression, substance use disorder, anxiety disorder, and attention deficit hyperactivity disorder were the most common psychiatric diagnoses among inmates. The prevalence of many psychiatric diagnoses was significantly higher in female inmates than in male inmates. Both yoga and freely chosen physical activity reduced self-directed aggression during incarceration, but the improvement was better in the group that preformed yoga.

Conclusion: The study provides evidence that yoga made on a regular basis have a positive effect on reducing self-directed aggression. Since no side effects of yoga exercise have previously or in this study detected, it can be concluded that yoga can be effective measure to increase inmates well-being.