In 2021, two very interesting systematic reviews appeared on the efficacy of Augmentative Alternative Communication in the linguistic enhancement of children with neurodevelopmental disorders. Crowe and colleagues  is even a mega-review (ie a systematic review of systematic reviews). The result is this extraordinary table that summarizes all the systematic reviews analyzed showing results and recommendations. The general conclusions reaffirm the effectiveness of PECS, AAC to modify behavior and develop social skills.
The second review, by Langarika-Rocafort and colleagues  focuses on primary school children with more than one diagnosis. The review shows a documented effectiveness of Augmentative Alternative Communication interventions in improving communication skills, in particular phonological awareness, vocabulary, the ability to make requests and the development of narrative skills. Above all, the achievement of better results is emphasized when children have the choice the preferred Augmentative Alternative Communication tool.