Schema therapy versus any control group for adult mental health disorders: a protocol for a systematic review with meta-analysis and trial sequential analysis

Background Mental health disorders are among the heaviest global health burdens. While many psychotherapies are effective for mental health disorders, some patients may require more specialized psychotherapies. Schema therapy, a transdiagnostic psychotherapy, addresses childhood adversity and personality characteristics which have been shown to predict and maintain more ingrained mental health disorders. The effects of schema therapy have previously been assessed in systematic reviews, but these suffered from methodological shortcomings and did not include the most recent trials. This systematic review with meta-analysis aims to synthesize the evidence of beneficial and harmful effects of schema therapy for a broad array of mental health disorders, taking into account the risk of both systematic errors, random errors, and certainty of evidence. Methods This systematic review with meta-analysis will contain a comprehensive search for relevant published and unpublished trials in major clinical databases and clinical trial registries. We will include randomized clinical trials comparing schema therapy to a control group for adult mental health disorders including attention deficit hyperactivity disorder, autism spectrum disorders, psychotic disorders, dissociative identity disorder, depressive disorders, bipolar disorders, anxiety disorders, obsessive-compulsive disorder, substance abuse, trauma- and stressor-related disorders, eating disorders, and personality disorders. Primary outcomes will be symptom severity and quality of life. Secondary outcomes will be serious adverse events, level of functioning, and treatment dropout. Risk of bias will be assessed with the Cochrane Risk of Bias tool version 2, an eight-step procedure will be used to assess if the thresholds for clinical significance are crossed, the risk of random errors will be assessed with Trial Sequential Analysis, and the certainty of the evidence will be assessed by Grading of Recommendations, Assessment, Development and Evaluations (GRADE). Discussion Schema therapy is a promising intervention for more severe cases of mental health disorders, but the certainty of evidence for benefits and harms of schema therapy is still unclear. This review will inform clinical guidelines, thus expanding the possible choices of treatments in clinical practice. Further, the review will provide a comprehensive overview of the literature and highlight research gaps to inform future research. Systematic review registration PROSPERO, CRD420251015725