Abstract
BACKGROUND: Recent data suggest that individuals with intellectual disability and borderline intellectual functioning are at greater risk of experiencing loneliness compared to the general population. This review aimed to explore how loneliness is perceived among these groups and to identify possible factors associated with it. METHOD: A systematic review was performed following PRISMA guidelines, covering four databases. The methodological quality of the included studies was assessed using a standardized assessment tool. RESULTS: Forty studies met the inclusion criteria, yielding a sample-size-weighted mean of loneliness of 41.70% in individuals with intellectual disability; evidence for borderline intellectual functioning was limited to one study (24.20%). Loneliness was associated with factors at the individual, social, and structural levels. CONCLUSIONS: Loneliness is a prevalent issue among individuals with intellectual disabilities and borderline intellectual functioning. Further research is required to examine more thoroughly the associated factors and guide the development of effective interventions. TRIAL REGISTRATION: PROSPERO: CRD420251022668.