Schizophrenia and Crimes

freedom-of-compulsions-habits-and-addictions-paulo-zerbatoSchizophrenia is a brain disease that entails a complex symptomology: substance abuse, psychotic symptoms, and flat affect. Patients with this disease either have damaged or absent neuro-anatomical structures, such as the thalamus, prefrontal cortex, and basal ganglia; these neural structures are associated with veridical-perception, affect, and higher-order cognitive states (Kandel, 2003; Torrey, 2013). Because of such neural deficiencies, Schizophrenics subjectively experience the world in a radically different manner; for instance, what typical people perceive as dangerous behavior, such as standing on a window ledge, schizophrenics may perceive as a necessary measure to hide from hallucinated demons or monsters (Torrey, 2013). Clearly, the patient may think such behavior is perfectly rational, but schizophrenics are often unaware that they are experiencing hallucinations or delusions: Anosognosia (Frith, 2015). So, even though the patient experiences their behavior as not dangerous, the symptoms of Schizophrenia, evidently, increase the likely hood of the patient engaging in dangerous behavior.

Schizophrenics not only engage in dangerous behavior but also criminal behavior. Schizophrenics’ commit violent crimes at a rate higher than the average person (Wallace et al., 2004). Unfortunately, having a diagnosis of schizophrenia is correlated with a 4.0 to 6.0 increase in the probability of committing a violent crime; violent crime definitions, cultural behavior, and public support vary amongst cultures and societies (Wallace et al., 2004; Hodgins et al., 2005), which can explain the 2.0 variance in the data. Moreover, although having a diagnosis of schizophrenia increases the probability of committing a violent crime, only 20% of those diagnosed with schizophrenia ever commit a violent crime (Torrey, 2013). So, if violent crime amongst schizophrenic populations is to be understood, then research on relevant variables ought to be looked at; more specifically, do schizophrenics who abuse substances commit more violent crimes than schizophrenics who do not: lifestyle or symptoms. However, it is important to consider more than lifestyle and symptoms, for there are many more causal mechanisms that induce violent criminal behavior in schizophrenics: schizophrenia is a multi-factorial illness (Torrey, 2013). And, even furthermore, one variable, such as substance abuse, will ultimately be insufficient for explaining the complexity of any human behavior, given that human behavior is multi-dimensional (Reisberg, 2014). So, this essay will explore other important variables as well, such as conduct disorder, lack of treatment, and comorbidity.



14GRAYMATTER-articleInline-v3In non-schizophrenic populations, the criminology research community understands that there is a statistical relationship between criminal behavior and substance use. To elaborate, individuals who are arrested must fill out a survey called the Computerized Lifestyle Assessment Instrument (CLAI), and the CLAI measures the lifestyles of criminals (Borchu et al., 2001). The CLAI survey had found that three-quarters of arrested individuals have consumed alcohol in the last six months and 60% had done so within the four weeks prior to arrest (Brochu et al., 2001). Additionally, one-third of those who completed the survey also reported illicit drug use one week prior to arrest. (Brochu et al., 2001). And, most interestingly, the survey had also found that 77% of those arrested believe that if they had not used drugs, then they would have not committed the crime (Brochu et al., 2001). Evidently, the criminology community has empirical grounds to theorize about the role of substance use in criminal behavior. So, do these same statistical correlations show for individuals with schizophrenia?

Yes, Schizophrenics that commit violent crimes often have a substance use disorder. However, that is not the entire picture. Of those who have schizophrenia and commit violent crimes, a 95% correlation with psychotic symptoms occurs (Wallace, 2004); furthermore, a 90% co-morbidity rate between psychotic symptoms and substance abuse exists (Soyka, 2000). And, on top of that, for schizophrenics who experience psychotic symptoms and do not commit violent crimes, a 90% comorbidity rate for substance abuse and psychotic symptoms is present (Hodgins et al., 2005). So, in other words, given that substance abuse is associated with psychotic symptoms, it is unknown whether the drugs or symptoms cause the patient to engage in violent crime.

In general, schizophrenics abuse substances; about 85% abuse alcohol or nicotine (Hodgins et al., 2005), which are known to exacerbate psychotic symptoms (Hodgins et al., 2005), and psychotic symptoms are also known to induce violent behavior (Torrey, 2013). In fact, if someone has a genetic predisposition to schizophrenia, then the use of psychoactive substances has the potential to not only induce psychotic symptoms but also induce an early onset of schizophrenia (Torrey, 2013). Moreover, the reason Schizophrenics often give for their substance abuse is that the use of substances helps them cope with their affect decay, delusions, and hallucinations; essentially, the high prevalence of substance abuse is a form of self-medication (Torrey, 2013). Thus, until a researcher develops a method to measure rates of violent crimes amongst schizophrenics who do not abuse substances, the question of substance abuse being causal in violent crimes amongst schizophrenia is an unanswerable one.

Even though substance abuse and psychotic symptoms cannot be separately studied, the lifestyle of substance abuse can be. That is, whether the lifestyle and areas of congregation for substance abusing schizophrenics leads to an increase in violent behavior or not.

One study found that 15% of the schizophrenics participating had committed theft for monetary gain to support a drug addiction at some point in time (Hodgins et al., 2005). Furthermore, two variables associated with violent behavior in schizophrenia are persecutory and paranoid delusions (Soyka, 2000), which can be brought on by substance use; many psychotic symptoms are a result of hyperactivity in the mesolimbic and cortical-limbic pathways (Frith, 2015), and illicit substances such as marijuana are known to stimulate activity in these areas (Frith, 2015), which then brings on psychotic symptoms. So, substance abuse in a social setting may lead to more violent crime because of how the substances influence on the brain. Even furthermore, many illicit substances have an environmental component to their psycho-active influence, so the experience received from the drug depends on the tone of the surroundings (Torrey, 2013); for example, a drug house will induce a negative experience given the potential dangers, whereas one’s personal house may induce a positive experience given the sense of security. Now, given that paranoia often leads to irrational and violent behavior, then an environmentally induced paranoia may lead to violent behavior; and, to be noted, many schizophrenics do spend much of their time in deviant areas (Torrey, 2013). Lastly, the sheer presence of others simply increases the odds of violent outbursts being directed towards a person. Clearly, the lifestyle associated with substance abuse can lead to an increase in violence.

Another contributing factor is that many schizophrenics are on antipsychotics while consuming other illicit substances. That is, certain illicit substances, such as hallucinogens, are known to provoke psychotic symptoms in schizophrenics when mixed with antipsychotics (Torrey, 2013). And since hallucinogens have the capacity to cause psychotic symptoms in healthy populations, it is quite dangerous to mix antipsychotics with hallucinogens. So, drug mixing plays a role in the explanation of violent schizophrenics. On top of the abuse of hallucinogens, some patients will stop their medication because of substance abuse. Patients who stop using their medication, or cannot access treatment anymore, experience an increase in violent behavior as well (Torrey, 2013). Another study found that substance abuse influences the patient’s willingness to seek treatment, which can lead to an increase in violent behavior (Hodgins et al., 2005).

The last variable that must be discussed is conduct disorder. Conduct disorder has an 80% comorbidity rate with schizophrenia (Hodgins et al., 2005). Conduct disorder is also associated with physical abuse, substance abuse, an earlier onset of schizophrenia, and a 2.6 increase in probability for committing violent crimes (Hodgins et al., 2005). Additionally, each symptom of conduct disorder seems to increase the likely hood of violent behavior, not just the diagnosis (Hodgins et al., 2005); that is, each anti-social behavior associated with conduct disorder seems to increase the likely hood of violent crime. Furthermore, a comorbid diagnosis of schizophrenia and conduct disorder entails a greater risk for violent criminal behavior than having a diagnosis of conduct disorder only (Hodgins et al., 2005). Conduct disorder complicates the entire situation because it is also a multi-factorial disorder (Hodgins et al., 2005).



tumblr_niuro4fbJN1svku1yo1_500Schizophrenia is clearly associated with an increased risk for violent behavior, substance abuse, and crime. The cause may vary from psychotic symptoms, lifestyle, or conduct disorder, but, nevertheless, schizophrenics are 4.0 to 6.0 more likely than the general public to commit a violent crime. If science is to ever thoroughly understand Schizophrenia and its relation to violent crime, more research is required. Schizophrenics often maintain a lifestyle that is neither conducive to treatment or psychotic symptoms, nor well suited for their needs; because of their lifestyle, comorbid disorders, and substance abuse rates, the degree of complexity a future research program must cover increases by 10fold. For instance, future research ought to consider more thoroughly context dependent decision making of schizophrenics, given that schizophrenics spend considerable amounts of time in deviant areas, which may explain some of the criminal behavior.

One of the primary limitations of current research is the lack of knowledge about the nuances of a schizophrenic’s lifestyle. There is a need for more knowledge about environmental invariants; more specifically, the social circles, family support, and income. Environment plays a substantial role in substance use; for instance, Marijuana and Alcohol are more addictive than other illicit substances because they are socially acceptable (Linden, 2012). So, whether schizophrenics associated with more substance abusers or not is relevant knowledge. Additionally, family support has been known to mitigate substance abuse and violent behavior (Torrey, 2013). So, whether the average patient has readily available family support or not is, as well, relevant for future research. Lastly, income may influence whether schizophrenics choose to steal to support their habits or not. So, whether patients can maintain a decent income is certainly important for future research.



Beebee, H., Hitchcock, C., & Menzies, P. C. (2012). The Oxford handbook of causation. Oxford: Oxford University Press.

Brochu, S., Cousineau, M.-M., Gillet, M., Cournoyer, L.-G., Pernanen, K. & Motiuk, L. (2001, January). Drugs, alcohol, and criminal behaviour : a profile of inmates in canadian federal institutions. Forum on Corrections Research, 13(3), 20-24.

Frith, C. D. (2015). The cognitive neuropsychology of schizophrenia. London: Psychology Press, Taylor & Francis Group.

Hodgins, S., Tiihonen, J., & Ross, D. (2005). The consequences of Conduct Disorder for males who develop schizophrenia: Associations with criminality, aggressive behavior, substance use, and psychiatric services. Schizophrenia Research,78(2-3), 323-335. doi:10.1016/j.schres.2005.05.021

Linden, D. J. (2012). The compass of pleasure: how our brains make fatty foods, orgasm, exercise, marijuana, generosity, vodka, learning, and gambling feel so good. New York: Penguin Books.

R, E. K. (2003). Principles of neural Science. Cambridge: McGrawHill.

Reisberg, D. (2014). The Oxford handbook of cognitive psychology. New York: Oxford University Press.

Soyka, M. (2000). Substance misuse, psychiatric disorder and violent and disturbed behaviour. The British Journal of Psychiatry,176(4), 345-350. doi:10.1192/bjp.176.4.345

Torrey, E. F. (2013). Surviving Schizophrenia: a Family Manual. HarperCollins.

Wallace, C., Mullen, P. E., & Burgess, P. (2004). Criminal Offending in Schizophrenia Over a 25-Year Period Marked by Deinstitutionalization and Increasing Prevalence of Comorbid Substance Use Disorders. American Journal of Psychiatry,161(4), 716-727. doi:10.1176/appi.ajp.161.4.716




Ideasinhat is a business development analyst and longtime reader of academic literature. He writes books and essays on science and philosophy, and posts them to this website. The essays, as with the books, cover topics from psychology, philosophy, and cognitive science to economics, politics, and law.

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