Method of homicide and severe mental illness: A systematic review

There is limited research that has examined offense characteristics in homicides committed by individuals with mental illness and with differing psychiatric diagnoses. The aim of this systematic review is to synthesize previous findings of studies analyzing homicide behavior by mentally ill individuals, and reporting any associations between mental illness and method of homicide. We searched four databases (MedLine, PsychINFO, Web of Science and Embase), and identified 52 relevant articles for analysis. Of these 52 articles, nine reported specific information on mental illness and method of homicide. Five out of nine articles revealed an association between schizophrenia/delusional disorder and the use of sharp instruments as a method of homicide. Four out of nine studies revealed an association between mood disorders (bipolar disorder/major depression) and strangulation/asphyxiation/suffocation/drowning. Our review confirms consistency across studies reporting a significant association between close contact methods and schizophrenia/mood disorders. Also identified as possible influential factors concerning weapon choice are illness duration, victim characteristics and planning/lack of planning of the homicide. Additionally, studies revealed up to 96% of severely mentally ill offenders experienced psychiatric symptoms at the time of the homicide. Future research may examine the presence of specific psychiatric symptoms when a mentally ill offender commits a homicide and whether these may be more influential in the method of homicide used than the psychiatric diagnosis of the offender.