McCarberg 1999.

Methods	RCT; 2 arms; assessed pre‐treatment, 6 months follow‐up
Participants	End of treatment n = 245 Start of treatment n = 353 Sex: 264 F, 89 M Mean age = 52.1 (SD 9.6) Source = pain or rehabilitation clinic Diagnosis = mixed chronic pain, many chronic low back pain Mean years of pain = 9.6
Interventions	"Cognitive behaviour therapy" "minimal home study"
Outcomes	Primary pain outcome: MPI pain severity Primary disability outcome: MPI pain interference Primary mood outcome: MPI affective distress Catastrophising outcome: none 11‐point box scale: pain severity                 Pain discomfort scale: pain distress                  Multidimensional Pain Inventory: pain severity                       Multidimensional Pain Inventory: affective distress                            Multidimensional Pain Inventory: self control                        Multidimensional Pain Inventory: interference                        Multidimensional Pain Inventory: social support and spouse behaviour subscales
Notes	CBT versus active, follow‐up: analyses 2.1, 2.2, 2.3 Yates quality scale: total quality = 11/35, design quality = 9/26, treatment quality = 2/9
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"Patients were randomized using a computer‐generated random number list"
Allocation concealment (selection bias)	High risk	Not reported
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	No attrition during treatment, only at follow‐up; no test for differences
Selective reporting (reporting bias)	Low risk	Fully reported
Blinding of outcome assessment (detection bias) All outcomes	High risk	Not reported