A digitally embedded intervention to enhance psychological decentering and reduce depression severity in at-risk adolescents: a randomised controlled trial of the ‘One Step Back’ programme

Background: Adolescence is a critical period for early mental health interventions. Scalable, evidence-based interventions for at-risk adolescents without severe symptoms are limited. We developed a low-intensity, digital programme to train psychological decentering (the ability to disengage from unwanted thoughts, feelings, and memories) as a core psychotherapeutic process for improving mental health. Methods: A two-arm randomised controlled trial compared a 5-week psychological decentering training (‘One Step Back’: OSB) programme with an active control (CTL) comprising physical and cognitive exercises (May 2021 to November 2022; ISRCTN14329613). Adolescents at-risk of depression were recruited through UK secondary schools, then randomised into trial arms (n = 114, 84% female; M age = 16.8 years, SD = 0.79). The primary outcome was self-reported decentering post-intervention measured using the Experiences Questionnaire. Secondary outcomes included symptoms of depression, anxiety, anger, and socio-emotional functioning, measured using standardised inventories. Analysis of covariance models were calculated, adjusting for baseline scores with an intention-to-treat approach. Findings: OSB was associated with improvements in self-reported decentering scores at post-intervention compared with CTL (M difference = 4.16 [95% CI 1.85–6.51]; p = 0.002; Cohen's d = 0.61). OSB participants reported decreased depression (M difference = -5.54 [95% CI -9.14 to -1.93]; p = 0.003, d = -0.60) and increased well-being (M difference = 4.53 [95% CI 1.21–7.86]; p < 0.001, d = 0.76). Interpretation: Psychological decentering was selectively trained in at-risk adolescents through a brief digital intervention. Training resulted in significant reductions in depression severity. Findings support this low-intensity approach to support adolescents before symptoms worsen. Funding: This project was funded by a Wellcome Strategic Award (Wellcome Ref 104908/Z/14/z; awarded to TD, S-JB, WK, and J. Mark G. Williams) and the UK Medical Council (Grant Reference: MC_UU_00030/5; awarded to TD). The contribution of MPB was partially supported by a Wellcome Trust Active Ingredients in Mental Health Commission. RCK was funded by an Economic and Social Research Council Doctoral Fellowship (ref SUAI/067). SJB is funded by Wellcome (grant number WT107496/Z/15/Z), the MRC, the Jacobs Foundation, the Wellspring Foundation, and the University of Cambridge.