To combine the results of earlier comparison studies of in‐patient aggression to quantitatively assess the strength of the association between patient factors and i) aggressive behaviour,ii) repetitive aggressive behaviour.

A systematic review and meta‐analysis of empirical articles and reports of comparison studies of aggression and non‐aggression within adult psychiatric in‐patient settings.

Factors that were significantly associated with in‐patient aggression included being younger, male, involuntary admissions, not being married, a diagnosis of schizophrenia, a greater number of previous admissions, a history of violence, a history of self‐destructive behaviour and a history of substance abuse. The only factors associated with repeated in‐patient aggression were not being male, a history of violence and a history of substance abuse.

By comparing aggressive with non‐aggressive patients, important differences between the two populations may be highlighted. These differences may help staff improve predictions of which patients might become aggressive and enable steps to be taken to reduce an aggressive incident occurring using actuarial judgements. However, the associations found between these actuarial factors and aggression were small. It is therefore important for staff to consider dynamic factors such as a patient's current state and the context to reduce in‐patient aggression.