Kole‐Snijders 1999.

Methods	RCT; 3 arms; assessed at pre‐treatment, post‐treatment, 6 months, 1 year
Participants	End of treatment n = 133 Start of treatment n = 148 Sex: 94 F, 54 M Mean age = 30.8 (SD 9.1) Source = pain or rehabilitation clinic Diagnosis = chronic low back pain Mean years of pain = 9.8
Interventions	"operant + cognitive coping skills" "operant + group discussion" "waiting list"
Outcomes	Primary pain outcome: no data available Primary disability outcome: no data available Primary mood outcome: no data available Catastrophising outcome: none (all reduced by factor analysis to 3 scores: motoric, coping control, negative affect)        Pain Behaviour Scale Checklist for Interpersonal Pain Behaviour Behavioural approach test (walking distance) Multi dimensional Locus of Control Pain Cognition Checklist Coping Strategies Questionnaire Nijmegen Hyperventilation Questionnaire Visual analogue scale: pain McGill Pain Questionnaire: pain
Notes	No data Yates quality scale: total quality = 28/35, design quality = 20/26, treatment quality = 8/9
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	“independent researcher blindly drew [numbers assigned randomly to patients] and assigned to one of three conditions”
Allocation concealment (selection bias)	Low risk	independent researcher
Incomplete outcome data (attrition bias) All outcomes	Low risk	Fully reported
Selective reporting (reporting bias)	Unclear risk	Reported as factor scores
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Assessor unaware of treatment condition