Factors Affecting Communication Outcomes for Deaf and Multilingual Learners: A Systematic Review.

The 17 included studies were too heterogeneous to combine. Sample sizes were small, languages varied, and 42 different outcome tools were used. Many studies did not describe the interventions participants received, so it is unclear whether outcomes were due to therapy, home language use, school setting, amplification or other supports. The review excluded studies of children using signed and spoken language together, so it does not speak to bimodal bilingual deaf children. It included only English-language publications and excluded research before 2001, so relevant non-English or older evidence may be missing. The authors could not assess risk of bias with a suitable tool and noted that all studies lacked detailed analysis plans, so selective outcome reporting cannot be ruled out. All review authors were hearing, White and from the linguistic majority, and no deaf, hard of hearing or multilingual individuals were consulted.

Do not read this review as proof that bilingual speech-language therapy causes better outcomes. The studies were heterogeneous, intervention details were often missing, and no pooled effect estimates were possible, so the findings describe factors associated with outcomes rather than tested treatment effects.