Violence and Mental Illness

The relationship between violence and mental illness is a challenging issue that clinicians face. The association between the two is commonly linked together in popular media and society, resulting in an exaggerated and misunderstood perception of mental illness. Clinicians are often placed in a difficult position of being asked to assess the risk that a patient could pose to the public, while also being asked by society/law to keep an individual's personal liberties in mind (e.g. - involuntary admissions).

• Large scale meta-analyses have shown that even categorizing individuals at “high risk” of violence had very little effects of predicting violence on a population level. One study demonstrated that to prevent one homicide, 35,000 “high-risk” schizophrenia patients would need to be detained.^[1]

• Individuals with mental illness can be at higher risk for violence based on certain biological, psychological, and social factors:^[2]
  • Biological factors include gender (male), temperament/impulsivity, and a family history of violence
  • Psychological factors include antisocial attitudes and poor problem solving approaches
  • Social factors include poor parent-child relations, social learning or antisocial behaviour, and victimization in childhood.
• The top three factors that are implicated in those who have a higher risk of violence compared with the general population: (1) severe mental illness, (2) substance abuse and/or dependence, and (3) a past history of violence.
  • Individuals with all of these risk factors have a distinctly higher than average risk of violence (severe mental illness alone does not predict risk of violence).^[3]
• These individuals should have a more structured violence risk assessment done, such as with the HCR-20.
• In acute psychiatric settings, young age, male sex, history of psychiatric illness, comorbid substance abuse and positive symptoms of a psychotic disorder have also been shown to be predictors of violent behaviour.^[4]

• Unfortunately, research has consistently shown that psychiatrists cannot predict future violence with any significant degree of accuracy.^[5][6]
• Thus, the use of validated rating tools may be one way to at least systematically document risk.

• The failure of higher control systems in the prefrontal cortex to modulate aggressive acts triggered by anger-provoking stimuli play a role in violence and aggression.Siever, L. J. (2008). Neurobiology of aggression and violence. American Journal of Psychiatry, 165(4), 429-442. Imbalances between the prefrontal regulatory influences and hyper-responsivity of the amygdala and other limbic regions also play a role.

• Actuarial tables can be used to estimate risk factors for violence. These estimates are usually based on static risk factors (using a specific algorithm that uses a combination of risk factor selection and weighting).
• Examples of actuarial instruments for violence include the:
  • Violence Risk Appraisal Guide (VRAG)
  • Sex Offender Risk Appraisal Guide (SORAG).
• Examples of actuarial instruments for sexual recidivism include the
  • STATIC-99R
• Strengths of using these instruments is that they are transparent, strongly associated with violence, can be used by non-clinical decision makers, and generates a numerical probability and percentile rank of the risk.
• However, disadvantages of these instruments is that the generalizability of the risk to a specific patient is limited.

• Structured clinical judgement tools like the Historical Clinical Risk Management-20 (HCR-20) allow clinicians to define static and dynamic risk factors for violence. The clinician combines these factors and arrives at a risk assessment. These tools are meant to promote flexibility in risk assessment, and allows for interprofessional input.
• However, the use of these tools are also not perfect.^[7]

• The Historical Clinical Risk Management-20 (HCR-20), is a validated violence risk assessment tool for adults aged 18 and above who may pose a risk for future violence.. It is the most commonly used violence risk assessment instrument.^[8]
• The HCR-20 can be used in both general, civil, and forensic populations, and assesses the future risk for violence to others.^[9]

• The Dynamic Appraisal of Situational Aggression (DASA) is a brief, 7-item scoring instrument to aid health care professionals in identifying patients with an increased risk of violence, in order to enable focused preventative interventions to reduce risk of imminent violence.^[10]