Cross-language generalization of language treatment in multilingual people with post-stroke aphasia: A meta-analysis.

Studies on the efficacy of language treatment for multilingual people with post-stroke aphasia and its generalization to untreated languages have produced mixed results. We conducted a systematic review and a meta-analysis to examine within- and cross-language treatment effects and the variables that affect them. We searched PubMed, PsycINFO, CINAHL, and Google Scholar (February 2020; January 2023), identifying 40 studies reporting on 1573 effect sizes from 85 individuals. We synthesized effect sizes for treatment outcomes using a multi-level model to correct for multiple observations from the same individuals. The results showed significant treatment effects, with robust within-language treatment effects and weaker cross-language treatment effects. Age of language acquisition of the treatment language predicted within-language and cross-language effects. Our results suggest that treating multilingual people with aphasia in one language may generalize to their other languages, especially following treatment in an early-acquired language and a later-learned language that became the language of immersion.