Background: 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.
Aims: To determine the prevalence of mental ill-health in adults with intellectual disabilities and to investigate factors independently associated with it.
Method: Population-based study (n=1023) with comprehensive individual assessments modelled using regression analyses.
Results: 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.
Conclusions: 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.