Exploring the Relationship Between Mental Health and Violent Behaviour

Mental Health - New Connections Psychology


When it comes to violent behaviour, there are multiple factors at play that interact with one another. This is an important point to consider, as public opinion often assumes a direct link between mental illness and violence. In a national survey conducted in 2006, it was revealed that 60% of Americans believed individuals with schizophrenia were prone to violent acts, while 32% held the same view about people with major depression.

However, research indicates that this perception does not align with reality. Most individuals with psychiatric disorders do not exhibit violent tendencies. Although there is a subset of individuals with such disorders who commit acts of violence, it is difficult to determine the extent to which mental illness contributes to this behaviour compared to other factors like substance abuse.

One of the challenges in studying this topic is that different research studies have employed various methods to assess rates of violence among both individuals with mental illness and control groups. Some studies rely on self-reporting, where participants recall their own violent actions. However, these studies may underestimate violence rates due to factors such as participants forgetting past actions or feeling embarrassed to admit their violent behaviour. Other studies compare data from the criminal justice system, such as arrest rates, but these inherently involve only a subset of individuals and may not accurately represent violence rates in the broader community. Moreover, some studies fail to account for multiple variables beyond substance abuse that contribute to violent behaviour, such as poverty, family history, personal adversity, and stress.

The MacArthur Violence Risk Assessment Study aimed to address the shortcomings of previous research by employing three sources of information to assess violence rates. Participants were interviewed multiple times to obtain ongoing self-reported data on violent behaviour, and their recollections were cross-verified with input from family members, case managers, and other individuals familiar with the participants. In addition, the researchers examined arrest and hospitalization records.

The study revealed that 31% of individuals with both a substance abuse disorder and a psychiatric disorder (known as a “dual diagnosis”) had committed at least one act of violence within a year. In comparison, 18% of individuals with a psychiatric disorder alone exhibited violent behaviour. These findings confirmed previous research indicating that substance abuse plays a significant role in violent behaviour. However, upon further investigation by comparing rates of violence in a specific neighbourhood in Pittsburgh, while controlling for environmental factors and substance use, no significant difference was found in the rates of violence between individuals with mental illness and other residents of the neighbourhood. In other words, after accounting for substance use, the study’s reported violence rates likely reflected factors common to that neighbourhood rather than symptoms of a psychiatric disorder.

Several studies comparing large cohorts of individuals with psychiatric disorders and their peers in the general population have contributed to the understanding of mental illness and violence by meticulously controlling for multiple contributing factors.

In two well-designed studies, researchers from the University of Oxford analysed data from a Swedish registry that recorded hospital admissions and criminal convictions. By utilizing this registry, which provides a unique personal identification number for everyone, the researchers were able to determine the number of individuals with mental illness who had been convicted of crimes and compare them with a matched control group. The findings indicated that individuals with bipolar disorder or schizophrenia had a slightly higher likelihood of engaging in assaults or other violent crimes compared to the general population. However, when comparing patients with bipolar disorder or schizophrenia to their unaffected siblings, the differences in violence rates diminished. This suggests that shared genetic vulnerability or common aspects of the social environment, such as poverty and early exposure to violence, partially contribute to violent behaviour. Nevertheless, the rates of violence increased significantly in those with a dual diagnosis (see “Rates of violence compared”).

When combined with the MacArthur study, these papers present a more intricate understanding of the relationship between mental illness and violence. They suggest that, similar to aggression in the general population, violence by individuals with mental illness is the result of multiple overlapping factors that interact in complex ways. These factors include family history, personal stressors (such as divorce or bereavement), and socioeconomic elements (such as poverty and homelessness). Substance abuse often becomes intertwined with these factors, making it challenging to isolate the influence of less apparent contributors.


Evaluating the Risk of Violence

High-profile acts of violence committed by individuals with mental illness not only influence public perception but also place clinicians under pressure to assess their patients’ potential for violent behaviour. While it is possible to make a general assessment of relative risk, predicting a specific act of violence is impossible since such acts often occur in highly emotional states. During a clinical session, the same individual may present as guarded, less emotional, and even thoughtful, masking any signs of violent intent. Even when a patient explicitly expresses an intention to harm someone else, the relative risk of acting upon that plan is significantly influenced by various life circumstances and clinical factors.

History of violence is a significant predictor of future violent behaviour, with individuals who have a prior arrest or history of violence being more likely to engage in violent acts again. However, it is challenging to ascertain whether past violence was due to mental illness or other factors explored below.

Substance use also plays a role, as patients with a dual diagnosis are more prone to violence compared to those with a psychiatric disorder alone. Therefore, a comprehensive assessment should include inquiries about substance use in addition to symptoms related to mental illness. One theory suggests that alcohol and drug abuse can trigger violent behaviour in individuals with or without psychiatric disorders due to impairments in judgment, emotional equilibrium, and cognitive inhibitions. In individuals with psychiatric disorders, substance abuse can exacerbate symptoms such as paranoia, grandiosity, or hostility. Moreover, patients who abuse substances are less likely to adhere to treatment for mental illness, potentially worsening their psychiatric symptoms.

However, another theory posits that substance abuse may be masking or intertwined with other risk factors for violence. For instance, a survey of 1,410 schizophrenia patients participating in the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) study found that substance abuse and dependence increased the risk of self-reported violent behaviour fourfold. Nevertheless, when adjusting for other factors like psychotic symptoms and conduct disorder during childhood, the impact of substance use lost significance.

Personality disorders, such as borderline personality disorder, antisocial personality disorder, and conduct disorder, often manifest as aggression or violence. When a personality disorder coexists with another psychiatric disorder, the combination may further elevate the risk of violent behaviour, as suggested by the aforementioned CATIE study.


The nature of symptoms also plays a role, with patients experiencing paranoid delusions, command hallucinations, and intense psychotic thoughts being more prone to violence compared to other patients. Understanding a patient’s own perception of these psychotic thoughts is important for clinicians, as it may indicate when a patient feels compelled to fight back.

Age and gender are additional factors to consider. Young people are more likely than older adults to engage in violent behaviour, and men are more prone to violence than women.

Social stress, including poverty, homelessness, and low socioeconomic status, increases the likelihood of violence.

Personal stress, crises, or recent losses, such as unemployment, divorce, separation, or being a victim of violent crime, also elevate the risk of violent behaviour.

Early exposure to aggressive family conflicts during childhood, physical abuse by a parent, or having a parent with a criminal record raises the risk of violence.


Preventing Violence

Research suggests that providing adequate treatment for mental illness and substance abuse can help reduce rates of violence. For example, in one study, the CATIE investigators analysed violence rates among patients who had been randomly assigned to antipsychotic treatment (with corroborating input from family members). The study revealed that patients with schizophrenia who adhered to antipsychotic treatment were less likely to engage in violent behaviour compared to those who did not comply. However, patients diagnosed with conduct disorder during childhood presented an exception to this trend. The study did not identify a specific medication as superior to others in reducing violence rates, but it excluded clozapine from its analysis.

Clozapine, an antipsychotic, has been shown to be more effective than other medications in reducing aggressive behaviour in patients with schizophrenia and other psychotic disorders, according to multiple studies. For instance, one study found that individuals diagnosed with schizophrenia or another psychotic disorder and treated with clozapine had significantly lower arrest rates than those taking alternative medications. However, the study did not determine whether this outcome was due to the drug itself or the fact that clozapine treatment requires frequent follow-ups, which may encourage patients to adhere to the prescribed regimen.

Nevertheless, it is important to note that medication treatment alone is unlikely to sufficiently reduce the risk of violence in individuals with mental illness. Interventions should ideally encompass long-term strategies and incorporate various psychosocial approaches, such as cognitive behavioural therapy, conflict management, and substance abuse treatment.

Unfortunately, achieving this ideal treatment is increasingly challenging in the real world due to reductions in reimbursements for mental health services, shorter hospital stays, inadequate discharge planning, fragmented community care, and limited options for individuals with a dual diagnosis. The Schizophrenia Patient Outcomes Research Team (PORT) guidelines outline the multimodal treatment required to improve the chances of full recovery, but most individuals with schizophrenia do not receive the recommended level of care. Addressing these challenges will require solutions from policymakers rather than clinicians.


Online Therapy

Online therapy, also known as teletherapy or e-therapy, has emerged as a convenient and accessible alternative to traditional in-person therapy. Through secure video conferencing platforms, individuals can receive professional counselling and mental health support from the comfort of their own homes. Online therapy offers numerous advantages, including greater flexibility in scheduling appointments, eliminating geographical barriers, and increased privacy for those who may feel more comfortable discussing sensitive topics from a familiar environment. It has become particularly valuable during times of social distancing and limited physical interaction. With advancements in technology and the growing acceptance of online platforms, online therapy has proven to be an effective and convenient option for individuals seeking mental health support.



In conclusion, understanding the relationship between mental illness and violence requires a nuanced perspective that considers the complex interplay of various factors. While public perception often assumes a direct link, research shows that most individuals with psychiatric disorders are not violent. Substance abuse, personal and social stressors, history of violence, and certain symptoms or disorders can contribute to an increased risk of violent behaviour, but it is crucial to recognize that these factors interact in intricate ways. Adequate treatment for mental illness and substance abuse, along with comprehensive interventions addressing psychosocial factors, can help reduce rates of violence. Furthermore, the emergence of online therapy provides a convenient and accessible option for individuals seeking mental health support. By embracing a holistic approach and utilizing the available resources, we can work towards creating safer communities and promoting the well-being of individuals affected by mental health challenges.

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