Schizophrenia and Crime

Many countries have a law that defends individuals from being responsible for the crimes they committed while under the influence of mental illnesses. This is known as the insanity defense, which the media often blame for an increase in violent crime rates. One infamous incident that comes to mind is the “2016 Taipei Neihu Murder,” where a man who previously sought treatment from a psychiatric hospital committed a brutal random murder of a four-year-old girl in front of her mother in broad daylight. The man eventually received a life sentence instead of the death penalty, leaving Taipei City fearful and resentful of the fact that many murderers would face abolished responsibility. The purpose of this article is not to discuss the moral or legal implications of the insanity defense. Rather, it is to explore the stigma that surfaces from these cases: violent crimes are often committed by people with mental illnesses. Even though there is an association between crimes and schizophrenia, it can be explained by a mediator: substance abuse.

An earlier study conducted by Lindqvist et al. investigated the connection between crimes and schizophrenia patients, as well as the types of crime committed by those patients compared to the general population. It found that female schizophrenia patients alone are twice as likely as the general population to commit crimes; but for male schizophrenia patients, there was no difference in crime rate compared to the general male population. Additionally, the rate of violent crimes is four times higher among schizophrenia patients. The results specifically showed that 13% of the violent offenders in the study were women, which is higher than the five to ten percent female contribution in national figures of corresponding crimes. In terms of criminal activity after conviction, only “one of the women in the cohort committed two or more violent offences during the follow-up period, whereas seventeen received two verdicts of violence, and three men were guilty of three violent offences each” (Lindqvist et al., 1990).  The study not only pointed to higher crime rates in the population with schizophrenia, but also a gender disparity in crimes committed by schizophrenia patients. 

While earlier studies aimed to find the association between crime and schizophrenia, recent studies focus on mediating the relationship between the two variables. Substance abuse is thought to be one of the strongest mediators. A study conducted by Fazel et al. investigated the severity of the crimes committed by persons with schizophrenia. They found it to be 4 to 6 times the level of those committed by persons without schizophrenia, and this can be explained by a comorbidity of substance abuse. According to the paper, “The rate of violent crime in individuals diagnosed as having schizophrenia and substance abuse comorbidity (27.6%) was significantly higher than in those without comorbidity (8.5%)” (Fazel et al., 2009). This shows that comorbid substance abuse is associated with higher violent crime rates in individuals with schizophrenia. 

One explanation for comorbid substance abuse as a mediator of the relationship between crime and schizophrenia is that, similar to schizophrenia, substance intake can also have a toll on a person’s cognitive ability. Common symptoms experienced by schizophrenia patients, such as hallucinations and delusions, may be present after alcohol and drug consumption, making substance abuse a risk factor for violent or criminal behavior. An article written by Tsimploulis et al. contests with the previous studies that substance use disorder can increase the risk of offending in persons with schizophrenia, especially among women. Moreover, the study found, “The percentages of substance abuse among NGRI [not guilty by reason of insanity] subjects with schizophrenia ranged from 35.7% to 74%” (Tsimploulis et al., 2018), demonstrating that there is an inverse relationship between criminal responsibility and schizophrenia patients with substance abuse problems. 

Altogether, many studies have established a link between schizophrenia and rates of criminal offences higher than the general public. More recent studies point to substance abuse as a mediating factor that contributes to this increased rate. The effect of schizophrenia itself on criminal offences is more obvious in women, and so is the effect of substance abuse on offending patients diagnosed with schizophrenia. Nevertheless, this association does not justify the stigma that all individuals with schizophrenia are dangerous. Similar to the effects of drugs and alcohol abuse, hallucinations and delusions can cause a person to behave abnormally. We should have compassion for the individuals struggling with these pathologies to achieve destigmatization. 



Fazel, S., Långström, N., Hjern, A., Grann, M., & Lichtenstein, P. (2009). Schizophrenia, substance abuse, and violent crime. JAMA, 301(19), 2016–2023.

Lindqvist, P., & Allebeck, P. (1990). Schizophrenia and Crime: A Longitudinal Follow-up of 644 Schizophrenics in Stockholm. British Journal of Psychiatry, 157(3), 345-350. doi:10.1192/bjp.157.3.345

Tsimploulis, Georgios MD*; Niveau, Gérard MD, PhD†; Eytan, Ariel MD, PhD*; Giannakopoulos, Panteleimon MD, PhD*; Sentissi, Othman MD, PhD* Schizophrenia and Criminal Responsibility, The Journal of Nervous and Mental Disease: May 2018 – Volume 206 – Issue 5 – p 370-377 doi: 10.1097/NMD.0000000000000805

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