Annelies A. de Bildt

Background Effects of staff provided positive behaviour support (PBS) for individuals with intellectual disabilities are unclear. Method Using a multicentre non‐randomised cluster controlled design, 26 teams of residential group homes, including 245 staff members of 167 individuals with intellectual disabilities, were allocated to a PBS or control group. Conducting multilevel analyses ( n = 123) we examined individuals' changes in irritability, other challenging behaviours and quality of life. Results Compared to controls, irritability did not significantly decrease more in the intervention group, but lethargic behaviours did. Personal development and self‐determination significantly increased. Irritability of individuals in the PBS group with higher levels of irritability or lower levels of intellectual disability significantly reduced more compared to controls. Conclusions PBS was effective in reducing irritability of individuals with severe levels of irritability or intellectual disabilities. Moreover, PBS decreased lethargic behaviours and improved several domains of quality of life.