What do systematic reviews say?

Ability to control anger: Provocation Inventory (PI) ‐ self report: Post‐treatment (scale range 0 to 75; higher scores indicate higher levels of aggression) · outwardly aggressive behaviour in people with intellectual disability

Aggressive behaviour: severity of incidents: Aberrant Behaviour Checklist (ABC – irritability subscale – key worker report – post‐treatment (Analysis 1.2.1) · outwardly aggressive behaviour in people with intellectual disability

Adaptive behaviour · outwardly aggressive behaviour in people with intellectual disability

Mental state: psychiatric symptoms measured using the Brief Symptom Inventory (BSI) (Analysis 1.27) · outwardly aggressive behaviour in people with intellectual disability

Quality of life ‐ self reported: Comprehensive Quality of Life Scale: Intellectual Disability (COMQoL‐ID: Post‐treatment · outwardly aggressive behaviour in people with intellectual disability

Cost of service utilisation · outwardly aggressive behaviour in people with intellectual disability