Similar results have been found by epidemiological and primary-care studies in different countries (e.g. Kessler et al., Treatment rates increase with age. Data from the national surveys of Australia, the United States and Switzerland show that treatment is most prevalent in the age groups 45 and over, and particularly low among those under age 35. Eurobarometer data confirm this pattern, showing a continuous increase of treatment rates across age groups (Figure 3.4). The average of the 21 OECD countries is 9% for younger people (15-24 years), 14% for adults (25-54 years), and 17% for seniors (55-64 years). Source: OECD calculations based on national health surveys for disorder prevalence, and Eurobarometer 2005 for treatment rates.