Behavioural and Cognitive Psychotherapy: page 1 of 6 doi:10.1017/S135246581800067X Does Behavioural Activation Lack Credibility Among Those Who Need It Most? A Comparison of Responses to Rationales for Behavioural Activation and Schema Therapy S. Curley School of Psychology, University of Adelaide, North Tce, Adelaide, SA 5005, Australia M.F. Smout School of Psychology, Social Work and Social Policy, University of South Australia, GPO Box 2471, Adelaide, SA 5001, Australia L.A. Denson School of Psychology, University of Adelaide, North Tce, Adelaide, SA 5005, Australia Background: Behavioural activation (BA) is an effective front-line treatment for depression but some consumers find it unattractive or aversive, and its rationale unconvincing. Aims: To investigate whether individual differences in symptoms of depression, borderline personality pathology or adverse childhood events would: (1) influence ratings of BA treatment credibility; (2) predict credibility rating differences in comparison to schema therapy (ST) exemplifying a contrasting theoretical rationale with a significant developmental history focus; (3) a third aim was to test whether BA credibility was increased by providing research evidence of its efficacy. Method: In an online within-subjects experiment, 219 Australian community adults completed the Credibility/Expectancy Questionnaire following written descriptions of BA and ST (presentation order randomized across participants), and again for BA after receiving information about research supporting BA’s efficacy. Results: Higher childhood adversity (but not severity of depression or borderline personality disorder symptoms) predicted lower BA credibility. Overall, ST was rated more credible than BA, but presenting BA evidence increased BA credibility ratings to match ST. This response was moderated by individual differences: participants with higher childhood adversity or previous therapy experience found ST more credible than BA even after receiving BA evidence. Conclusions: Individuals are not equally receptive to BA. Presenting research evidence is an effective strategy for increasing credibility, but additional intervention or tailoring the rationale is recommended for clients with significant childhood adversity. Keywords: behavioural activation, rationale, schema therapy, treatment credibility Correspondence to Matthew Smout; e-mail: matthew.smout@unisa.edu.au © British Association for Behavioural and Cognitive Psychotherapies 2019