Schizophrenia is associated with a larger range of autoimmune diseases than heretofore suspected. Future research on comorbidity has the potential to advance understanding of pathogenesis of both psychiatric and autoimmune disorders.

There is substantial evidence that alcohol, tobacco, and cannabis dependence problems surface more quickly when use of these drugs starts before adulthood, but the evidence based on other internationally regulated drugs (e.g., cocaine) is meager. With focus on an interval of up to 24 months following first drug use, we examine drug-specific and age-specific variation in profiles of earlyemerging clinical features associated with drug dependence. Based upon the United States National Surveys on Drug Use and Health (NSDUH) conducted in 2000-2002, the risk of experiencing drug dependence problems was robustly greater for adolescent recent-onset users of cocaine, psychostimulant drugs other than cocaine, analgesics, anxiolytic medicines, inhalants drugs, and cannabis, as compared to adult recent-onset users (odds ratio=1.5~4.3, p<0.05). This was not the case for the NSDUH hallucinogens group (e.g., LSD). The adolescent onset associated excess risk was not constant across all clinical features. Our evidence suggests promoting earlier detection and interventions, as well as greater parent and peer awareness of drug dependence clinical features that may develop early among young people who have just started using drugs.

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By describing patterns of disease distribution within populations, identifying risk factors, and finding associations, epidemiological studies have contributed to our current understanding of schizophrenia. Advanced paternal age and the association with auto-immune diseases are some of the newly described epidemiological finding in schizophrenia epidemiology, shaping our current definition of schizophrenia. Though early intervention strategies have gained momentum, primary prevention of schizophrenia still seems a very distant aspiration. In this article we review the major epidemiological features of schizophrenia, with particular attention to the recent advances using population-based data. We also discuss some pervasive myths in schizophrenia epidemiology, such as the universal distribution and the gender equality myths. Review of the available evidence shows that schizophrenia does not distribute itself equally across cultures and countries, and the disease is more prevalent among males.

Schizophrenia was associated with a greater variety of autoimmune diseases than was anticipated. Further investigation is needed to gain a better understanding of the aetiology of schizophrenia and autoimmune diseases.

Prospective evidence on illegal drug use in particular subpopulations may be needed to better understand health problems among users at different life stages and the possible long-term effects.

Nosologic, methodological and substantive reasons for observed age-related excess in occurrence of marijuana dependence problems among early onset users deserve more attention in future research.

This new epidemiological evidence suggests that crack-smoking may increase risk of cocaine dependence once cocaine use starts, but we cannot rule out the possibility that crack users start out with a greater susceptibility to become cocaine dependent.