The effectiveness of psychotherapeutic interventions for negative psychotic symptoms: A systematic review and meta-analysis

Negative symptoms, such as emotional flatness, social withdrawal, and lack of motivation, will be considered in this study as often overlooked in psychosis treatment, despite their significant impact on long-term recovery and rehabilitation. While positive symptoms (e.g., hallucinations and delusions) are typically prioritized in clinical diagnosis and treatment, negative symptoms will frequently persist, creating substantial barriers to social reintegration and functional recovery. Aim: The goal of this meta-analysis is to evaluate the effects of psychological interventions on negative symptoms of psychosis, drawing on evidence from randomized controlled trials comparing psychotherapy treatments to control groups. Methods: Searches are conducted in PubMed, EMBASE, and PsycINFO (up to March 1, 2025). Data extraction and Risk of Bias assessments will be performed by two independent raters, using the Cochrane Risk of Bias 2 tool. The main outcome assessed will be the reduction of negative psychotic symptoms at post-test, measured using Hedges’ g, based on the effect size and a random effects model. Subgroup analysis will be conducted based on therapy format and therapy type. Additionally, the analysis will explore the moderating effects of study characteristics (sample size, treatment duration), participant characteristics (age, gender, illness duration) and risk of bias. Sensitivity analyses will be performed to test the robustness of findings by identifying and excluding outliers.