The online mindset intervention 'The Growth Factory' for adolescents with intellectual disabilities: moderators and mediators.

The study was small for the question it asked. With 119 participants there was not enough power to detect the interaction effects being tested, so a real difference in who benefits may have been missed. Satisfaction was measured only in the 60 adolescents who received the programme, with no comparison group for that analysis. Five adolescents with mild intellectual disability dropped out before the first assessment because they could not manage the questionnaires, which may bias what the study can say about level of disability. The research assistants collecting the questionnaires knew which group each participant was in, which could have influenced the answers. Ratings of satisfaction may have partly reflected a wish to please the researchers. One of the mindset scales, emotion and behaviour, had weak internal consistency, so results based on it should be read cautiously. Only one possible explanation for the programme's effects, perseverance, was tested, and its measurement was indirect. The comparison group received usual care rather than an active comparison intervention, so the size of any effect might differ against a different comparator.

Two of the authors developed the online intervention being tested. The trial was funded by the F. Couvee-Stichting, Johanna Kinderfonds, Stichting Rotterdams Kinderrevalidatie Fonds Adriaanstichting, the University of Amsterdam and Pluryn, and the paper states that none of these contributors had any role in the design, data collection, management, analysis, interpretation or writing of the manuscript.

Do not read the satisfaction finding as proof that making the programme more enjoyable would make it work better. Satisfaction was measured only in the adolescents who received the programme, with no comparison group, and the authors say those ratings may partly reflect a wish to please the researchers, so what causes what is unclear. Do not treat the gender findings as settled either. They come from a large set of interaction tests in a small sample that the authors themselves describe as underpowered for this kind of analysis.