A systematic review for improving research into psychiatric disorders in adults with epilepsy and comorbid intellectual disabilities

BACKGROUND AND OBJECTIVES: Intellectual disability (ID) and psychiatric disorders are common comorbidities of epilepsy, yet there is a paucity of rigorous research evaluating the frequency and features of this experience. This systematic review seeks to evaluate the methodological strengths and limitations of extant literature, with the aim of providing a practical framework for future research to better understand this complex comorbidity. METHODS: Searches of EMBASE, MEDLINE, Web of Science, CINAHL and PsycINFO scanned January 2000 to June 2024. Eligibility criteria included peer-reviewed studies in English, participants over 16 years old with ID and epilepsy, and reporting psychiatric symptoms or disorders. Methodological quality was rated with a traffic light system. RESULTS: Nineteen studies were included. Methodological evaluation revealed most studies recruited from representative settings such as epilepsy services or national ID databases. Most studies included variability in ID severity. While a majority of studies used ID-appropriate psychiatric measures, only 12 % directly included the person with ID in this assessment and they were seldom involved in the research consent process. While more than half of studies reported antiseizure medication use, there was limited evaluation of ASM dose relationships with psychiatric presentations. DISCUSSION: A framework for future research is proposed that focuses on ensuring representative samples, interdisciplinary research to improve diagnosis of psychiatric conditions in this population, and greater inclusion of people with epilepsy and ID in the research process so that researchers can better understand their needs and vulnerabilities so as to improve clinical translation.