Background Changes in positive and negative symptom profiles during acute psychotic episodes may be key drivers in the pathway to violence. Acute episodes are often preceded by fluctuations in affect before psychotic symptoms appear and affective symptoms may play a more important role in the pathway than previously recognised.Methods We carried out a prospective cohort study of 409 male and female patients discharged from medium secure services in England and Wales to the community. Measures were taken at baseline (pre-discharge), 6 and 12 months post-discharge using the Positive and Negative Syndrome Scale. Information on violence was obtained using the McArthur Community Violence Instrument and Police National Computer.Results The larger the shift in positive symptoms the more likely violence occurred in each 6-month period. However, shifts in angry affect were the main driving factor for positive symptom shifts associated with violence. Shifts in negative symptoms co-occurred with positive and conveyed protective effects, but these were overcome by co-occurring shifts in anger. Severe but stable delusions were independently associated with violence.Conclusions Intensification of angry affect during acute episodes of psychosis indicates the need for interventions to prevent violence and is a key driver of associated positive symptoms in the pathway to violence. Protective effects against violence exerted by negative symptoms are not clinically observable during symptom shifts because they are overcome by co-occurring anger.