The impact of initial depression and anxiety levels on symptom severity change during psychological treatment for common mental disorders: a systematic review

BACKGROUND: Depression and anxiety are highly comorbid conditions, which may impact treatment response. AIMS: We intended to examine how depression and anxiety symptoms change during psychological interventions for adults and how the initial severity is associated with distinct trajectory classes. METHODS: We identified papers examining longitudinal changes in depression and anxiety. Trajectory classes were grouped into responders, improvers and non-improvers. Narrative synthesis, alongside meta-analysis, was applied to explore the number and nature of classes, their associations with study characteristics and predictors of trajectory class membership. This study was pre-registered on International Prospective Register of Systematic Reviews (PROSPERO) (CRD42023393155), and the authors followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidance. RESULTS: We identified 18 papers, including 22 models with two to six classes. Responding and non-improving classes prevailed. Meta-regression revealed no characteristics associated with the proportion of these classes. Initial depression and anxiety levels predicted trajectory class membership for each other, but not always non-response. Unemployment, suicidality, social functioning impairment, treatment type and medication use predicted following non-responding trajectory. CONCLUSION: Our findings highlight the complex relationship between initial anxiety and depression severity and their changes during psychological interventions. They provide practitioners with insights into factors associated with non-response patterns of symptom change.