McPhail 1989.

Methods	Randomised controlled trial Setting: study conducted in Scotland; adult training centre No study dates are given
Participants	12 participants (mean age 34 (35 in intervention group and 33 in control group) with mild‐to‐severe intellectual disabilities on BPVS (mean mental age in both groups was 7)) Participants who were eligible were judged to be disruptive by instructors and staff at a day centre as reported on a 10‐point severity scale of 17 disruptive behaviours. It would appear that the scale was developed for the study
Interventions	Treatment 1: abbreviated progressive relaxation (n = 6) Intervention was carried out by researchers who were familiar with the intervention No fidelity checks of the intervention were carried out Treatment 2: no treatment or "story reading" (n = 6)
Outcomes	Behavioural rating scale, 10‐item checklist
Notes	Data in published paper omitted SD and we did not receive a response from contacting the authors No information on source of funding No declaration of conflicts of interest statement
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No information provided. It is not clear how participants were randomised to treatment groups
Allocation concealment (selection bias)	Unclear risk	No information provided
Blinding of participants and personnel (performance bias) All outcomes	High risk	Participants and personnel were not blinded to group allocation
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Outcome assessors were blinded to group allocation
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants completed the intervention but data from 2 participants were removed from analysis; 1 participant from each group was removed from the analysis (1 was unwell for a week and the other showed no aggression at baseline). Quote: "One subject from each group was discarded from the analysis, one because she was ill for a week during treatment and the other because she showed almost no disruptive behaviour at baseline and throughout the study". The reasons provided for the removal of participants appear to be unrelated to the outcome
Selective reporting (reporting bias)	High risk	No data on the follow‐up study are presented in the paper, although the authors provide a reason for this. Quote: "The follow‐up study consisted of four observation sessions on two different days in two consecutive weeks, three months after the completion of the original study. Because of extensive changes within the centre, only three relaxation and three control group participants could be observed under similar conditions to that at the time of the original study"
Other bias	Low risk	No other sources of bias such as an imbalance of participant characteristics at baseline