Mental disorder in adults with intellectual disability. 1: Prevalence of functional psychiatric illness among a community-based population aged between 16 and 64 years.
One in seven community adults with ID has a second psychiatric disorder—screen with Mini PAS-ADD and follow up when life events strike.
01Research in Context
What this study did
The team asked how many adults with intellectual disability have a second mental illness. They visited people aged 16 to 64 who lived in the community, not in hospitals.
Each adult completed the Mini PAS-ADD screen. If results were high, a psychiatrist gave the full PAS-ADD interview to check ICD-10 criteria.
What they found
About one in seven adults met criteria for a functional psychiatric illness. Schizophrenia and strong phobias showed up more often than in the general public.
How this fits with other research
Tsakanikos et al. (2006) later asked the same question but split the group by autism status. They found no extra risk when autism and ID occur together, updating the 2001 picture.
Porter et al. (2008) tracked adults over time and added matched controls. They showed that low ability and Down syndrome, not autism, explain most mental-health differences. Their work sharpens the 2001 snapshot.
Hattier et al. (2011) zoomed in on anxiety alone in a larger sample. They reported a lower point rate of 3.8% and linked it to job loss and life events, extending the broader 2001 count.
Why it matters
The one-in-seven rate is your cue to screen every adult with ID. Use the free Mini PAS-ADD first; if scores are high, bring in a clinician for the full PAS-ADD. Later studies show the real drivers may be low ability or major life changes, so update risk profiles and add support when clients lose a job or caregiver.
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02At a glance
03Original abstract
The reported prevalence of psychiatric illness among adults with intellectual disability (ID) varies widely between 10 and 39%; however, many methodological problems exist. The aims of the present study were to establish the prevalence of functional psychiatric illness among adults with ID who live in the community, in order to compare the overall rate and types of psychiatric illness between the population with ID and the general population without ID, and to establish the risk factors associated with psychiatric illness in adults with ID. The study was done in two stages. In the first part, a trained psychiatrist interviewed 101 randomly selected adults with ID and their carers using the Mini Psychiatric Assessment Schedule for adults with Developmental Disability (Mini PAS-ADD) to screen for psychiatric caseness. Out of these 101 adults, 90 had sufficient communicative abilities that made the administration of Mini PAS-ADD possible. A second trained psychiatrist interviewed 19 out of the 20 adults who were diagnosed as psychiatric cases according to the initial Mini PAS-ADD interview. This psychiatrist interviewed patients and their carers in line with the full PAS-ADD interview. The second psychiatrist was blind to the initial diagnoses made according to the Mini PAS-ADD questionnaire. A final psychiatric diagnosis was made according to International Classification of Diseases - 10th Revision (ICD-10) criteria. Some 14.4% (95% confidence interval = 7.4-21.4%) of the cohort had a psychiatric diagnosis according to ICD-10 criteria: 4.4% had schizophrenia, 2.2% depressive disorder, 2.2% generalized anxiety disorder, 4.4% phobic disorder and 1% delusional disorder. The overall rate of functional psychiatric illness (point prevalence) was similar to that found in the general population (16%). However, the rates of schizophrenic illness and phobic disorder were significantly higher in the study cohort compared with those in the general population (0.4% and 1.1%, respectively). Increasing age and the presence of physical disability were significantly associated with the occurrence of psychiatric illness. Out of the 11 remaining adults with severe ID, two (18%) had a diagnosis of a psychiatric illness (one mania and one anxiety disorder) according to the Diagnostic Assessment for the Severely Handicapped (DASH) questionnaire.
Journal of intellectual disability research : JIDR, 2001 · doi:10.1046/j.1365-2788.2001.00374.x