Abstract
<p>Cognitive behavioural therapy (CBT) is a verbally mediated first-line treatment for anxiety and depression in young people. Developmental language disorders are common in this population, yet the impact of verbal ability on CBT response or drop-out remains unclear. This systematic review considered randomised controlled trials (RCTs) of CBT or CBT-based interventions in youth with anxiety or depressive disorders. Eligible studies reported anxiety, depression, or treatment adherence/drop-out as an outcome and include a measure of verbal ability or language-based selection criteria. We searched EMBASE, MEDLINE, PsycINFO, and CINAHL on 9th January 2025 and 4th January 2026. Sixty-eight studies were eligible. No studies recruited participants with developmental language disorders, and sixty-five studies excluded participants with poor verbal ability. Ten studies reported taking measures of verbal ability, while only one primary RCT and six secondary analyses examined the relationship between verbal ability and outcomes. Findings were mixed, and overall evidence quality was variable. Trials of standard CBT for anxiety and depression in youth systematically exclude individuals with poor verbal ability using subjective criteria, while rarely reporting participants' verbal ability. Consequently, evidence on whether verbal ability influences CBT outcomes is lacking. Further research is needed to determine the effectiveness of CBT for language disorders.</p>