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Comorbidity with mental disorders[edit | edit source]

Schizophrenia and bipolar disorder[edit | edit source]

Schizophrenia and bipolar disorder are generally considered to be distinct diagnoses, but people who show multiple symptoms of both disorders are often given the hybrid diagnosis schizoaffective disorder [1] The clinical features of such patients suggests that schizophrenia and bipolar disorder are variant expressions of a diathesis, because of the similar incidence,similar sex ratio and age at onset.

Comorbidity with physical disorders[edit | edit source]

Schizophrenia and drug use[edit | edit source]

The relationship between schizophrenia and drug use is complex, meaning that a clear causal connection between drug use and schizophrenia has been difficult to tease apart. There is strong evidence that using certain drugs can trigger either the onset or relapse of schizophrenia in some people. It may also be the case, however, that people with schizophrenia use drugs to overcome negative feelings associated with the commonly prescribed antipsychotic medication, and the disorder itself, where negative emotion, paranoia and anhedonia are all considered to be core features.

Hallucinogens[edit | edit source]

Schizophrenia can sometimes be triggered by heavy use of stimulant or hallucinogenic drugs, although some claim that a predisposition towards developing schizophrenia is needed for this to occur. There is also some evidence suggesting that people suffering schizophrenia but responding to treatment can have relapse because of subsequent drug use.

Drugs such as methamphetamine, ketamine, PCP and LSD have been used to mimic schizophrenia for research purposes, although this has now fallen out of favor with the scientific research community, as the differences between the drug induced states and the typical presentation of schizophrenia have become clear.

Hallucinogenic drugs were also briefly tested as possible treatments for schizophrenia by psychiatrists such as Humphry Osmond and Abram Hoffer in the 1950s. Ironically, it was mainly for this experimental treatment of schizophrenia that LSD administration was legal, briefly before its use as a recreational drug led to its criminalization.

Cannabis[edit | edit source]

There is increasing evidence that cannabis use can contribute to the onset of schizophrenia. Some studies suggest that cannabis is neither a sufficient nor necessary factor in developing schizophrenia, but that cannabis may significantly increase the risk of developing schizophrenia and may be, among other things, a significant causal factor. Nevertheless, some previous research in this area has been criticised as it has often not been clear whether cannabis use is a cause or effect of schizophrenia. To address this issue, a recent review of studies from which a causal contribution to schizophrenia can be assessed has suggested that cannabis doubles the risk of developing schizophrenia on the individual level, and may be responsible for up to 8% of cases in the population.48

Tobacco[edit | edit source]

It has been noted that the majority of people with schizophrenia (estimated between 75% and 90%) smoke tobacco. However, people diagnosed with schizophrenia have a much lower than average chance of getting and dying from lung cancer. While the reason for this is unknown, it may be because of a genetic resistance to the cancer, a side-effect of drugs being taken, or a statistical effect of increased likelihood of dying from causes other than lung cancer49.

It is argued that the increased level of smoking in schizophrenia may be due to a desire to self-medicate with nicotine. A recent study of over 50,000 Swedish conscripts found that there was a small but significant protective effect of smoking cigarettes on the risk of developing schizophrenia later in life.50 Whilst the authors of the study stressed that the risks of smoking far outweigh these minor benefits, this study provides further evidence for the 'self-medication' theory of smoking in schizophrenia and may give clues as to how schizophrenia might develop at the molecular level. Furthermore, many people with schizophrenia have smoked tobacco products long before they are diagnosed with the illness, and some groups advocate that the chemicals in tobacco have actually contributed to the onset of the illness and have no benefit of any kind.

Alcohol[edit | edit source]

Alcohol use by people with schizophrenia is a substantial complication.

Template:Schizophrenia - Comorbidity with alcohol

Schizophrenia and violence[edit | edit source]

Violence perpetrated by people with schizophrenia[edit | edit source]

Although schizophrenia is sometimes associated with violence in the media, only a small minority of people with schizophrenia become violent, and only a minority of people who commit criminal violence have been diagnosed with schizophrenia.

Research has suggested that schizophrenia is associated with a slight increase in risk of violence, although this risk is largely due to a small sub-group of individuals for whom violence is associated with concurrent substance abuse, active psychotic symptoms, and ceasing psychiatric drugs51. For the most serious acts of violence, long-term independent studies of convicted murderers in both New Zealand52 and Sweden53 found that 3.7%–8.9% had been given a previous diagnosis of schizophrenia.

There is some evidence to suggest that in some people, the drugs used to treat schizophrenia may produce an increased risk for violence, largely due to agitation induced by akathisia, a side effect sometimes associated with antipsychotic medication.54 Similarly, abuse experienced in childhood may contribute both to a slight increase in risk for violence in adulthood, as well as the development of schizophrenia.16

Violence against people with schizophrenia[edit | edit source]

Research has shown that a person diagnosed with schizophrenia is more likely to be a victim of violence (4.3% in a one month period) than the perpetrator55.

See also[edit | edit source]

References & Bibliography[edit | edit source]

  1. Blacker, D. & Tsuang, M. T. (1992).Contested boundaries of bipolar disorder and the limits of categorical diagnosis in psychiatry. Am. J. Psych. 149: 1473-1483]]
  • Achim AM, Maziade M, Raymond E, Olivier D, Merette C, Roy MA. How Prevalent Are Anxiety Disorders in Schizophrenia? A Meta-Analysis and Critical Review on a Significant Association. Schizophrenia Bulletin 2009.
  • Cunill R, Castells X, Simeon D. Relationships between obsessive-compulsive symptomatology and severity of psychosis in schizophrenia: a systematic review and meta-analysis. Journal of Clinical Psychiatry 2009; 70(1).
  • Fazel S, Gulati G, Linsell L, Geddes JR, Grann M. Schizophrenia and violence: systematic review and meta-analysis. PLoS Med 2009; 6(8).
  • Ferron JC et al. A review of research on smoking cessation interventions for adults with schizophrenia spectrum disorders. Mental Health and Substance Use: Dual Diagnosis 2009; 2(1):64-79.
  • Furtado VA, Srihan V, Kumar A. Atypical antipsychotics for people with both schizophrenia and depression. Cochrane Database of Systematic Reviews 2009; (4).
  • Hesdorffer DC, Rauch SL, Tamminga CA. Long-term psychiatric outcomes following traumatic brain injury: a review of the literature. Journal of Head Trauma Rehabilitation 2009; 24(6): 452-9.

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