Schizophrenia and alcohol abuse is a significant problem. After nicotine and smoking cigarettes, alcohol is the next commonest substance used by people diagnosed with schizophrenia. The Epidemiologic Catchment Area (ECA) study found that a third of people with schizophrenia had a comorbid alcohol use disorder. This is three times the rate in the general population. A number of negative consequences have been found to be associated with this: poor compliance with medication, increased physical morbidity, increased contact with criminal justice system and violence, increased admissions to hospital, greater psychosocial dysfunction, homelessness, poor insight, and suicidal behaviour. But which people with schizophrenia go on to develop an alcohol use disorder (abuse or dependence)? This is a clinically important question – so that appropriate treatment can be applied. It however remains difficult to answer.
Previous research have identified male gender, young age and a family history of an alcohol use disorder as risk factors for comorbid schizophrenia and alcohol abuse and dependence. However no differentiation was made between alcohol misuse and the misuse of other substances, and the temporal relationship between the two has not been defined.
A recent Swedish study released in June 2011 examined this question by doing a retrospective case control study involving more than 12,000 people. It attempted to determine the role of parental and sociodemographic risk factors.
12,653 people were followed up for 17 years, and 962 (7.6%) were diagnosed with comorbid alcohol use disorder. This was 11 times higher than found in a 9 year Swedish general population. However if one does have both disorders, then the likelihood of being diagnosed with either increases. Thus failure to diagnose pre-existing alcohol use disorder, could therefore increase the strength of the association.
This study found the following factors for comorbid alcohol use disorder in schizophrenia:
These factors were all found to be independent risk factors for alcoholism and schizophrenia.
Violent offending was found the strongest predictor of alcohol use disorder after being diagnosed with schizophrenia.
This study suggests that these factors should be specifically looked for and treated in people with schizophrenia. Brief interventions to reduce alcohol consumption in general populations appears to be effective, and may also be effective in a population with schizophrenia.
Other factors, though not examined in this study, might also be risk factors for development of alcohol use disorders in schizophrenia.