The relationship between paranoia and aggression in psychosis: A systematic review

Aggression in the context of schizophrenia has significant detrimental personal, clinical and societal implications. Whilst understanding the precise pathways to aggression in people with a diagnosis of schizophrenia is critical for risk management and treatment, these pathways remain unclear. A paranoid belief that others intend harm is one psychotic symptom that might contribute to aggressive behaviours. This is the first review to investigate the relationship between paranoia and aggression in psychosis. A systematic review of published literature pertinent to the relationship between paranoia and aggression was conducted. A search of online databases from inception to November 2014 was performed with keywords related to 'schizophrenia', 'paranoia' and 'aggression'. Fifteen studies, primarily cross-sectional in design (n = 9), met eligibility criteria. Studies reviewed showed mixed support for an association between paranoia and aggression in both inpatients and community settings. However, when study quality was taken into account, more methodologically rigorous studies tended to show a positive association between factors. Mixed findings are most likely due to important methodological shortcomings, including heterogeneous samples and studies using a diverse range of aggression/violence measures. In light of methodological limitations of individual studies reviewed, further investigation of the relationship between paranoia and aggression in psychosis using robust methodology is needed before definitive clinical recommendations regarding the hypothesised relationship between paranoia and aggression can be made. This paper sets out key recommendations for future studies, including operationalizing the specific components of aggression and paranoia under investigation and methods to delineate important mediators in the paranoia and aggression relationship.