The study by Cooper et al. (2006) investigates the prevalence and associated factors of mental ill-health among adults with intellectual disabilities. The research is based on a population-based study involving 1023 participants, using comprehensive individual assessments and regression analyses. The point prevalence of mental ill-health was found to be 40.9% (clinical diagnoses), 35.2% (DC-LD diagnoses), 16.6% (ICD-10-DCR diagnoses), and 15.7% (DSM-IV-TR diagnoses). Problem behaviors were the most prevalent type of mental ill-health. Factors independently associated with mental ill-health included more life events, female gender, type of support, lower ability, more consultations, smoking, incontinence, not having severe physical disabilities, and not having immobility. The study highlights the need for further longitudinal research and the development of appropriate interventions, public health strategies, and policies to address mental health issues in this population. The findings also suggest that ICD-10-DCR and DSM-IV-TR diagnostic criteria undercount mental ill-health compared to DC-LD.The study by Cooper et al. (2006) investigates the prevalence and associated factors of mental ill-health among adults with intellectual disabilities. The research is based on a population-based study involving 1023 participants, using comprehensive individual assessments and regression analyses. The point prevalence of mental ill-health was found to be 40.9% (clinical diagnoses), 35.2% (DC-LD diagnoses), 16.6% (ICD-10-DCR diagnoses), and 15.7% (DSM-IV-TR diagnoses). Problem behaviors were the most prevalent type of mental ill-health. Factors independently associated with mental ill-health included more life events, female gender, type of support, lower ability, more consultations, smoking, incontinence, not having severe physical disabilities, and not having immobility. The study highlights the need for further longitudinal research and the development of appropriate interventions, public health strategies, and policies to address mental health issues in this population. The findings also suggest that ICD-10-DCR and DSM-IV-TR diagnostic criteria undercount mental ill-health compared to DC-LD.