Schilling 2018.

Study characteristics
Methods	4‐week trial with 2 arms Metacognitive training for borderline patients (B‐MACT) Active control intervention (PMR) Duration of trial: 4 weeks Duration of participation: 4 weeks Country: Germany Setting: not stated
Participants	Method of recruitment of participants: recruited from the Deparment of Psychiatry of the Asklepios clinic, Germany Sample size: 48 Diagnosis of borderline personality disorder: Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM‐IV) Means of assessment: Structured Clinical Interview for DSM‐IV Axis II Disorders (SCID‐II) Mean age: B‐MACT = 29.36 years (standard deviation = 10.46), PMR = 31.15 years (standard deviation = 9.59) Sex: 91.7% female Comorbidity: 31% = major depressive disorder, 23% = any anxiety disorder (including 12 patients with PTSD), 7% = alcohol or substance abuse, 9% = dependence Inclusion criteria Diagnosis of borderline personality disorder Aged 18‐65 years old Exclusion criteria History of severe neurological disorder Intelligent quotient less than 70 Diagnosis of bipolar disorder Schizophrenia or dementia Alcohol or substance dependence with consumption in last 4 weeks
Interventions	Experimental group Treatment name: B‐MACT Number randomised to group: 22 Duration: 4 weeks Control/comparison group Comparison name: PMR Number randomised to group: 26 Duration: 4 weeks Both groups Concomitant psychotherapy: not stated Concomitant pharmacotherapy: yes; 56 of the 74 treated with psychotropic medication, not specified by group Proportions of participants taking standing psychotropic medication during trial observation period: unclear
Outcomes	Primary Borderline personality disorder severity, assessed by a translation of the clinician‐administered Zanarini Rating Scale for BPD (ZAN‐BPD) Secondary Depression, assessed by the Beck Depression Inventory Attrition, in terms of patients lost after randomisation in each group
Notes	Sample size calculation: no sample calculation Ethics approval: yes Comments from review authors: We received an additional article sent by email from Dr Schilling on 22 January 2019.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Comment: no information about randomisation method provided
Allocation concealment (selection bias)	Unclear risk	Comment: no information about allocation concealment provided
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Comment: no information about the blinding of assessors provided
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Comment: no data on attrition, no mention of ITT or imputation method
Selective reporting (reporting bias)	Unclear risk	Comment: no protocol found preventing us from making a clear assessment of reporting bias
Other bias	High risk	Treatment adherence Comment: no data on treatment adherence Allegiance bias Comment: first author was principal investigator and delivered both interventions. She also developed the manual for B‐ MACT. Attention bias Comment: interventions were similar in length.