Mental ill-health in adults with intellectual disabilities: prevalence and associated factors

Reported prevalence of mental ill-health among adults with intellectual disabilities ranges from 7 to 97%, owing to methodological limitations. Little is known about associations.To determine the prevalence of mental ill-health in adults with intellectual disabilities and to investigate factors independently associated with it.Population-based study (n=1023) with comprehensive individual assessments modelled using regression analyses.Point prevalence of mental ill-health was 40.9% (clinical diagnoses), 35.2% (DC-LD), 16.6% (ICD-10-DCR) and 15.7% (DSM-IV-TR). The most prevalent type was problem behaviours. Mental ill-health was associated with more life events, female gender, type of support, lower ability, more consultations, smoking, incontinence, not having severe physical disabilities and not having immobility; it was not associated with deprived areas, no occupation, communication impairment, epilepsy, hearing impairment or previous institutional residence.This investigation informs further longitudinal study, and development of appropriate interventions, public health strategy and policy. ICD-10-DCR and DSM-IV-TR undercount mental ill-health in this population compared with DC-LD.