Cooper 1989.

Methods	Randomised controlled trial
Participants	16 male Vietnam War veterans in the USA. All DSM‐III PTSD
Interventions	6 ‐ 14 90‐minute flooding sessions plus standard treatment (n = 8) vs standard treatment (n = 8)
Outcomes	STAI, BDI
Notes	No information was provided with regards to the therapists delivering treatment or any measures of treatment adherence.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Quote: "Efforts were made to preclude bias in assessment by maintaining as nearly random a procedure as possible" Comment: There were no details of the method of sequence generation, but the authors indicate that it was not entirely random.
Allocation concealment (selection bias)	High risk	Quote: "In all cases group assignment was pre‐decided before the participant agreed to participate...there were three exceptions to the rule of pre‐determined random assignment" Comment: Allocation does not seem to have been concealed.
Incomplete outcome data (attrition bias) All outcomes	High risk	All 16 participants provided posttreatment data, but 2 were removed from the analysis of data from the experimental group due to not completing therapy (1 from each group). These individuals were said to have a more severe presentation.
Selective reporting (reporting bias)	Low risk	Comment: All specified outcomes were reported.
Other bias	High risk	Comment: Very small sample.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Comment: Participants were aware of their allocation.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Self‐report measures only, but it is not clear how these were administered.