Applying a theory of change approach to evaluating evidence for circle of security interventions: a systematic review

Circle of Security (COS) interventions aim to improve parent-child relationships. Preliminary evidence of the effectiveness of COS interventions has been positive, but recent studies suggest mixed results that may be due to a lack of differentiation between different versions of COS interventions. This systematic review used a theory of change/program logic approach to summarize the evidence for COS interventions and to explore the conditions under which each protocol was most effective. A comprehensive systematic literature search was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for studies administering a verified COS intervention protocol with parents/caregivers of children aged 0-8 years. Studies were coded for study design, protocol type, sample characteristics, treatment fidelity, dose, risk of bias, and type of outcome. Nineteen eligible studies were included; seven were randomized controlled trials. Studies of the higher dose protocols (i.e., COS-Intensive, COS-Intensive-Revised Hybrid, COS-Perinatal Protocol) showed promising results across primary and secondary parent outcomes, longer term relationship and child outcomes, and clinical samples. Results showed mixed evidence for the efficacy of the more scalable COS-Parenting. Reviewing studies according to the theory of change/program logic suggested three sources of variability in COS-Parenting studies compared to the higher dose COS interventions that could impact outcome: treatment dose/strategies, sample type, and treatment fidelity. Differential effectiveness of COS interventions tested in seven randomized controlled trials, two nonrandomized controlled trials, and 10 single-arm trials suggests that different COS variants may be better suited to different target populations. (PsycInfo Database Record (c) 2025 APA, all rights reserved).