Neuropsychiatric decompensation in adolescents and adults with Phelan-McDermid syndrome: a systematic review of the literature.

The review relies entirely on case reports, which are subject to ascertainment bias and may not represent the general PMS population. Descriptions of symptoms and skill loss were often retrospective and lacked standardized measures, making it difficult to confirm whether losses met the criteria for true regression or were temporary effects of acute psychiatric episodes. Diagnosis of psychiatric conditions like bipolar disorder and catatonia is challenging in individuals with severe intellectual disability and limited speech, and many reports lacked sufficient detail to reliably confirm these diagnoses. Treatment responses were not systematically assessed, and the small number of patients receiving specific medications limits the ability to draw firm conclusions about efficacy.

The study was funded by the National Institute of Neurological Disorders and Stroke, the New York Community Trust Jules and Ethel Klein Fund, the Beatrice and Samuel A. Seaver Foundation, and the NIH Rare Disease Clinical Research Network. No specific conflicts of interest were declared by the authors in the provided text.

Do not interpret the reported treatment successes as evidence of proven efficacy. The review highlights that antipsychotics were often ineffective or harmful, while lithium and divalproex showed promise, but these conclusions are based on uncontrolled case reports with significant variability in dosing and outcome measures. Clinical decisions should be made with caution and in consultation with specialists familiar with PMS.