The results will be analysed on an intention to treat principle with all randomised participants, using all follow-up measures. Consequently, participants who filled out the questionnaire will be included in the analyses, regardless of whether or not they have completed the intervention. The baseline characteristics of the parents in both
research groups will be compared using Chi-squared tests for nominal and ordinal variables, and t-tests for continuous variables. The differences between the intervention and control condition over time will be assessed by mixed model techniques to consider factors that may influence the outcomes. If necessary, data on subjects lost to follow-up will be handled by extrapolation of the last observation or by sophisticated imputation techniques. Changes in the child’s psychosocial problems and parenting characteristics will be expressed as standardised effect sizes with 95% confidence intervals. The CONSORT guidelines will be followed [14]. All the analyses will be carried out using SPSS 17.0.