Pfropfschizophrenia in the age of deinstitutionalization: whose problem?

Intellectual disability co-occurring with schizophrenia and other psychiatric illness: population-based study

BACKGROUND

The epidemiology of intellectual disability co-occurring with schizophrenia and other psychiatric illness is poorly understood. The separation of mental health from intellectual disability services has led to a serious underestimation of the prevalence of dual diagnosis, with clinicians ill-equipped to treat affected individuals.

AIMS

To estimate the prevalence of dual diagnosis and describe its clinical profile.

METHOD

The Western Australian population-based psychiatric and intellectual disability registers were cross-linked (total n=245,749).

RESULTS

Overall, 31.7% of people with an intellectual disability had a psychiatric disorder; 1.8% of people with a psychiatric illness had an intellectual disability. Schizophrenia, but not bipolar disorder and unipolar depression, was greatly over-represented among individuals with a dual diagnosis: depending on birth cohort, 3.7-5.2% of those with intellectual disability had co-occurring schizophrenia. Pervasive developmental disorder was identified through the Intellectual Disability Register and is therefore limited to individuals with intellectual impairment. None the less, pervasive developmental disorder was more common among people with a dual diagnosis than among individuals with intellectual disability alone. Down syndrome was much less prevalent among individuals with a dual diagnosis despite being the most predominant cause of intellectual disability. Individuals with a dual diagnosis had higher mortality rates and were more disabled than those with psychiatric illness alone.

CONCLUSIONS

The facility to combine records across administrative jurisdictions has enhanced our understanding of the epidemiology of dual diagnosis, its clinical manifestations and aetiological implications. In particular, our results are suggestive of a common pathogenesis in intellectual disability co-occurring with schizophrenia.

Schizophrenia spectrum disorders in people with intellectual disabilities

PURPOSE OF REVIEW

To examine most recently published studies of schizophrenia spectrum disorders in people with intellectual disabilities.

RECENT FINDINGS

Studies that have been published in the review period have advanced understanding of the epidemiology, presentation, assessment, suspected neuropathology, genetics and treatment of, and service issues relating to, schizophrenia spectrum disorders in people with intellectual disabilities.

SUMMARY

The number of published studies investigating schizophrenia spectrum disorders in people with intellectual disabilities continues to increase slowly. The evidence base, however, needs to be strengthened, particularly by randomized controlled trials in pharmacotherapy, psychosocial interventions and service delivery.