These identity codes were matched against those generated by the prevalence study.

Even 12 months later, after the second prevalence study, more than half of the snowball group were still 'unknown' to the various agencies surveyed (see Table 5.8).

Table 5.8 demonstrates that a greater proportion of users known to both prevalence studies came from the two townships with higher levels of social deprivation.

Many regions of the world are not researched sufficiently, and for some major regions there are no prevalence studies at all (for example, in China).

One community-based prevalence study using the Rotterdam criteria found that about 18% of women had PCOS, and that 70% of them were previously undiagnosed.

Most national-level prevalence studies do not report psilocybin use; however, NSDUH does report lifetime use among adults and adolescents.

Epidemiologists say the wide variance in estimates from the prevalence studies that do exist support the idea that the disorder has not increased hugely.

National-level prevalence studies suggest that among adult users, marijuana use is highest among younger adults.

So far only three prevalence studies in Dutch and English adults have been based on double-blind, placebo-controlled food challenges.

A prevalence study and description of alli use by patients with eating disorders.