Chapter 23: Homicide and Mental Disorder

Homicide

• unlawful death purposefully inflicted on an individual by another individual

Importance of Studying Homicide

• loss of life

• public threat

• severe trauma to community and family/friends

  • post-traumatic stress disorder/depression

• need to learn more about and need to debunk misconceptions and stereotypes

Mental Disorder

• no one consistent definition for mental disorder

  • different studies use different definitions, measures, and clinical judgements

• classifications and definitions differ between sources

  • ICD

  • DSM

  • Psychiatric and Psychological Definitions

Worldwide Homicide Rate (2017)

• 6.1 per 100,000

General Homicide Rates

• general decline in homicide rates around the world

• increase in homicide rates in Central and Sourth America because of

  • drug markets

  • firearm availability

  • social inequalities

Mental Disorders Among Homicide Offenders

• few studies on the prevalence and incidence of mental disorders in homicide offenders

  • most are Western studies

Mental Disorders Most Commonly Found in Homicide Offenders

• schizophrenia

  • AND other types of psychotic disorders

• personality disorders

How Common are Mental Disorders Among Homicide Offenders

• 5-21% of homicide offenders have 1 or more mental disorders

• evidence suggests

  • homicide rates committed by an individual with a mental disorder are related to the total homicide raets of each country

    • factors other than mental health may contribute

Swinson et al., 2011 — Study

• overall homicide rate: 1.28 per 100,000

• examined rates of mental disorders among convicted homicide offenders in England

• psychosis = 0.07

• schizophrenia = 0.08

• found that 4% of homicide offenders were schizophrenic and 6% were diagnosed with psychosis

  • both diagnoses were at the time of the event

Golenkov et al., 2011 — Study

• overall homicide rate: 12.4 per 100,000

• examined rates of mental disorders among homicide suspects in Russia

• rate of schizophrenia in sample = 0.35 per 100,000

  • much higher than rates found in other countries

  • mental disorder and homicide could have common underlying factors

    • (cause a change in rates of schizophrenia when rates of homicide change)

Risk of Committing Homicide

• people diagnosed with mental disorder have a 10-20x greater risk of committing homicide — compared to the general public

• less than 1% of population has schizophrenia BUT 5-20% of homicide offenders are diagnosed with schizophrenia

  • schizophrenia is overrepresented among offenders compared to general population

Homicide Rates Before and After Treatment

• systematic review based on 10 Western studies was done examining homicide rates before treatment of psychosis vs. after treatment

  • before treatment

    • higher risk of homicide than general population especially if no treatment for those with psychosis

    • about 4 in 10 homicides were committed by individuals with psychosis

  • after treatment

    • about 15x lower

    • 1 in 10,000 people diagnosed with psychosis committed homicide

• importance of accessible treatment for those suffering with mental illness — psychosis does not cause homicide

Abnormal Homicides

• some researchers have referred to this as homicides committed by people who

  • were diagnosed with mental disorder shortly after the offense

  • were considered legally insane

  • recieved a diminished responsibility verdict

flaws:

• no clear inclusion/exclusion criteria

• no statisitcal evidence

• different definitions of mental disorder across studies

• not that simple

• results confounded by heterogeneous definitions of mental disorder

Mental Disorders Among Homicide Victims

• increased risk of victimization

• literature suggests

  • 6-22% of homicide victims have a mental disorder

  • mental disorder = 2-6x higher risk of victimization

Nationwide Cohort Study in Sweden — Homicide Rates Among People With Mental Disorder

• 1.8 per 100,000

Nationwide Cohort Study in Sweden — Homicide Rates Among People Without Mental Disorder

• 0.9 per 100,000

Nationwide Cohort Study in Sweden — Homicide Rates Among General Population

• 1.1 per 100,000

Nationwide Cohort Study in Sweden — Comparing Homicide Rates Among the General Population and Those With and Without Mental Illness

• individuals diagnosed with a mental disorder had an increased risk of becoming a victim of homicide (compared to the general population)

  • increased risk could be related to many comorbidities, including substance abuse

Comorbidity

• having 2 or more mental disorders at the same time

  • research suggests that having 2 or more mental disorders can increase the risk of

    • committing homicide

    • being a victim of homicide

Substance Abuse and Mental Disorder

• strong finding: substance abuse COMBINED with another mental disorder increases the likelihood of homicide

  • alcohol or drug abuse ↔ schizophrenia, psychosis, depression, personality disorders

Neilssen et al., 2007

• 73% of homicide offenders diagnosed with a mental disorder were also diagnosed with a substance abuse disorder BUT

  • substance abuse does not completely explain the relationship between mental disorder and homicide

*shouldn’t look at mental disorder in isolation — other factors like substance abuse could contribute

Methodological Limitations of the Research

• different definitions of mental disorder

  • different diagnoses, different definitions

    • studies of suspects vs. offenders causes differences in results

• studies are mostly descriptive and retrospective

  • always explaining what happened rather than why it happened

  • looking backwards

• limited geographical focus

  • countries with low homicidal rates

    • may not reflect what happens in countries with higher rates

  • many Western countries

Complex Relationship between Homicide and Mental Disorder

• there is an association between mental disorder and homicide

  • mental disorder = higher risk of becoming a homicide offender or victim

• NO causation

  • there is no research supporting the statement that mental disorder causes homicidal violence

• mental disorder DOES NOT = dangerous

  • important to challenge stigma and discrimination