During adolescence and young adulthood people appear to be more prone to violent behaviour. A greater tendency to violent behaviour appears to be associated with hyperactivity, impulsivity and low tolerance for frustration and provocation in social settings.

This prospective cohort study aimed to evaluate rates of violent behaviour among young people with mental disorders, compared with older age groups.

A total of 340 individuals with severe mental disorders (125 living in residential facilities and 215 out-patients) were evaluated at baseline with the SCID-I and II, Brief Psychiatric Rating Scale, Specific Level of Functioning scale, Brown–Goodwin Lifetime History of Aggression scale, Buss–Durkee Hostility Inventory, Barratt Impulsiveness Scale and State–Trait Anger Expression Inventory-2. Aggressive behaviour was rated every 15 days with the Modified Overt Aggression Scale (MOAS).

The sample comprised 28 individuals aged 18–29 years, 202 aged 30–49 and 110 aged 50 and over. Younger age was associated with a personality disorder diagnosis, substance use disorder, being single and employed. These results were confirmed even controlling for the gender effect. The patterns of the cumulative MOAS mean scores showed that younger (18–29 years old) individuals were significantly more aggressive than older (≥50) ones (P < 0.001).

This study highlights how young age in people with severe mental disorders is correlated with higher levels of impulsivity, anger and hostility, confirming previous analyses. Our results may assist clinicians in implementing early interventions to improve anger and impulsivity control to reduce the risk of future aggressive behaviours.