The statistical analyses were performed using SPSS 18. The data was analyzed on an intention-to-treat (ITT) basis. Missing values at baseline, post-intervention and follow-up were imputed with the use of SPSS Missing Value Analysis on the continuous measures with the expectation-maximization (EM) method. This method computes missing values based on maximum likelihood estimates using observed data in an iterative process [34]. The total percentage of missing data (T0-T1-T2) was 5%, due to unanswered items (0,6%) and incomplete assessments (4,4%). A comparison of results based on the imputed intention-to-treat sample versus the observed data revealed similar outcomes. Therefore, only the results from the intention-to-treat analyses are reported.