3. Suggested design for future trial.

Methods	Participants	Interventions	Outcomes
Allocation: randomised, clearly described	Diagnosis: people with schizophrenia or related disorders and history of aggressive behaviours	1. CBT plus standard care1	Aggression: Episodes of aggression (physical or verbal) Average endpoint or change score on aggression scale Agitation: Frequency of agitation Average endpoint or change score on agitation scale
Blinding: outcome assessors (due to nature of intervention)	N ~ 3002	2. Standard care3	Self‐harm: Suicide Frequency of self‐harm Adverse effects/events: Clinically important events
Duration: 3 to 6 months (endpoint), 6 to 12 months (follow‐up)			Global state: Use of additional medication (not intervention medication) Use of restraints or seclusion Leaving the study early: For any reason For a specific reason Others: Number of new admissions to health and correctional services Number of new contacts with mental services, justice system or police Compliance with treatment Psychiatric symptoms Level of functioning Number of relapses

CBT: cognitive behavioural therapy.

¹Psychological therapy for cognitive restructure of thoughts, emotions and behaviours that usually includes cognitive therapy and elements of behavioural therapy delivered individually or concurrently

³² Powered to be able to identify a difference of ~20% between groups for primary outcome with adequate degree of certainty.

³Normal level of care participants would receive for their condition