Abstract
Since 1992 six surveys have been carried out in Finland on the use of drugs by the general adult population. The samples of these studies have been drawn from the central population register, excluding people in institutions or without a permanent address. They seem to be fairly representative, but the methods of data collection have varied. Four of the studies used questionnaires, but telephone and face-to-face interviews have also been used. The response rates vary, partly because of the method of data collection. Therefore the results of these studies are not directly comparable.
The article summarizes the results of these studies concerning lifetime prevalence of cannabis use among men, women, and young adults (18–29 years). Using a simple mathematical model, it answers the following questions: 1) has the use of cannabis become more common? 2) To what extent have the differences in data collection methods and response rates affected the results?
The results of the analysis indicate that 1) in 1992–1996 the annual relative increase in the prevalence of cannabis use has been 9 per cent for men, 4 per cent for women, and 11 per cent for young adults; 2) in comparison with the results of mail surveys, telephone and face-to-face interviews yield considerably lower figures, especially among women; and 3) an increase of one percentage point in the response rate raises the prevalence figure by 3 per cent. Although these results are based on fairly large samples and are consistent with previous studies, it should be noted that the estimates are essentially based on the results of one particular study. Therefore some doubts remain about their generalizability.
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