Comorbid mental disorders and substance use disorders: epidemiology, prevention and treatment

The importance of general population research on comorbidity

Page last updated: 2003

It is critically important to study patterns of comorbidity between different mental disorders in general population samples. It is not possible to know that patterns observed in clinical samples will reflect those in the general community, because significant biases may be present (Berkson, 1946; Galbaud Du Fort, Newman, & Bland, 1993). There are a variety of reasons why comorbidity might be more common in clinical samples. It is also likely that skewed patterns of comorbidity will exist because of factors such as areas of particular interest, or expertise of clinicians in a given treatment centre, or alternatively, exclusionary policies of a treatment centre, or factors that may differentially influence a person's decision to seek help.

These factors are impediments to making accurate decisions about treatment needs of the general population from clinical samples. It is also difficult to make advances in theories about comorbidity since we do not know whether comorbidity observed in clinical samples is due to sampling, or referral biases. Only by studying representative samples of the general population can we ensure that our findings reflect general patterns of co-occurrence of different mental health problems in the community.