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Comorbid Substance Abuse and Schizophrenia

Schizophrenia and Substance Abuse

Patients that suffer from schizophrenia, a severe psychiatric disorder that effects approximately one percent of the population, also often suffer from a substance use disorder. In fact, 50 percent of patients with schizophrenia also suffer from a substance use disorder at some point during their life, and a combination of the two disorders create severe adverse effects for the patient.[1] Regarding treatment, if both disorders are not treated simultaneously, the patient’s prognosis is often poor.1

What is schizophrenia?

Schizophrenia is an interesting disorder, characterized by cognition disturbances and behavioral and emotional concerns.1 Some patients suffer from hallucinations, paranoia, and delusions.1 These symptoms can lead to cognitive deficits and social avoidance.1 Patients experience reduced brain volume in the prefrontal cortex and temporal lobes, which most likely cause these deficits.1 Schizophrenia is also  commonly associated with dopamine system dysfunction, and dopamine plays a large part in the reward- and pleasure-seeking symptoms.1 When an illicit drug is used, the function of the dopamine transporters are blocked, resulting in an increase in dopamine, or feelings of pleasure.1

Schizophrenia & Substance Use: Self-Medication or Vulnerability?

SchizophreniaThe link between schizophrenia and substance abuse has been explained best by two main, and different, hypotheses: the self-medication hypothesis (SMH) and the addiction vulnerability hypothesis (AVH).1 The SMH hypothesis states that drugs of abuse relieve some psychological suffering that a patient is undergoing, while the AVH hypothesis states that schizophrenia increases a person’s vulnerability to drug reward and reinforcement.1 SMH states that drug addiction is a reaction to schizophrenia, as it relieves depression, blunted affect, and neurocognitive deficits.1 However, as SMH focuses mainly on self-report measures, many researchers question the hypothesis’ validity.1 After conducting a study on the effects of smoking nicotine in schizophrenics, the hypothesis also states that smoking actually improves visuospatial working memory (VSWM).1 However, medicines can help increase VSWM without the use of nicotine and its harmful effects on the body.1 If the SMH hypothesis was supported, drug use would not be a problem for people with schizophrenia.1

On the other hand, AVH does not believe that there are any beneficial reasons for a person’s drug addiction.1 In fact, the hypothesis states that a person suffering from schizophrenia becomes addicted to drugs even thought there are negative consequences.1 The combination of environmental and genetic influences can also predispose an individual to a drug addiction, often before a psychiatric disorder appears.1

Identifying the reasons for comorbid drug addiction in persons with schizophrenia is difficult.1 There have been many theories proposed to explain such reasons, yet not one theory has encompassed all aspects yet.1 Therefore, more research is needed on the subject.1


[1] Bridgman, A., Ouellet-Plamondon, C., Morozova, M., & George, T. P. (2013, February 12). Understanding the Neurobiological Basis of Drug Abuse: Comorbidity in Schizophrenia | Page 3 – Psychiatric Times. Psychiatric Times. Retrieved February 19, 2013, from http://www.psychiatrictimes.com/schizophrenia/content/article/10168/2128032 Schizophrenia.

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