Assessing cannabis dependence in community surveys: methodological issues

Drug-related social role impairments and social maladaptation are referenced explicitly in the case definitions for drug dependence within DSM-IV-TR. Nonetheless, cases of drug dependence without this type of secondary consequence have been observed in recent epidemiological studies. When an 'impairment/maladaptation gating' approach has been taken during recent large-scale psychiatric surveys (for example, to reduce participant fatigue or burden), the net effect may include (a) a reduced number of identified drug dependence cases and (b) biases in the estimates of association linked to the occurrence of drug dependence. In this report, we probe these issues with respect to cannabis dependence, making use of data from the cross-sectional United States National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), a household survey of 43,093 adults aged 18 years and over. In this process, we shed light on actual impact of the gating approach mentioned above. Specifically, when we simulated a social impairment/maladaptation 'gated' assessment of cannabis dependence, the end result was a very modest reduction in the estimated prevalence of cannabis dependence. It suggested that for every 10 000 general population survey respondents there would be no more than 12 cases of cannabis dependence without the above-referenced impairments/maladaptations. Patterns of association linking suspected background characteristics to the prevalence of cannabis dependence were not appreciably different when the 'gated' and 'ungated' approaches were applied. In summary, there are reasons to take the ungated approach in detailed research on cannabis use and dependence. Nevertheless, in panoramic mental health surveys, the inefficiency of an 'ungated' approach must be balanced against the anticipated yield of cannabis dependence cases who lack social role impairments or socially maladaptive behaviours.