Alcohol use disorders (AUD) comorbidity has a high prevalence in schizophrenia: 21% to 51% of patients with schizophrenia had a lifetime history of alcohol abuse or dependence.

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Patients with AUD are more likely to be male and to present cannabis dependence. Conduct disorder, antisocial personality disorder, greater impulsivity and sensation seeking are established risk factors for AUD among patients with schizophrenia. Patients with schizophrenia reported greater euphoria and stimulatory effects in response to alcohol that may contribute to the increased risk for AUD (D'souza et al., 2006).

AUD have a negative impact on the course and outcome of schizophrenia, in particular, alcohol use may worsen the positive and cognitive symptoms of schizophrenia (Bowie et al., 2005). AUD are associated with depression and suicide behaviors in patients with schizophrenia. Patients with dual disorders have higher rates of medication nonadherence or number of hospitalizations. Despite lower alcohol exposure than in pure alcohol dependence, the comorbidity of schizophrenia with AUD compounds or accounts for brain volume abnormalities of schizophrenia in cortical prefrontal (Mathalon et al. 2003), cerebellar (Sullivan et al. 2000), pontine and thalamic (Sullivan et al. 2003) sites.

A number of theories have been proposed to explain the frequecy of the comorbidity. Dopamine-mediated mesocorticolimbic brain reward circuitry dysfunction in schizophrenia may explain the increased sensitivity to alcohol (Chambers et al. 2001, Green 2005). Atypical antipsychotics, particularly clozapine treatment, could be associated with reduced substance abuse.