What is already known on this topic

People with intellectual disability experience high rates of mental disorders and challenging behaviour, but representative data are hard to obtain for this population. Concerns have previously been raised about the difficulty this group experience in accessing quality mental health services1 and the morbidity associated with high rates of psychotropic drug prescription.2 General practitioners (GPs) are pivotal in provision of mental healthcare and representative data from this setting has the capacity to inform the epidemiology of mental disorders and the psychotropic drug burden for people with intellectual disability.

Methods of the study

Sheehan and colleagues conducted a longitudinal (1999–2003) cohort study of the prevalence of mental disorders and psychotropic drug prescription in adults with intellectual disability using data from a large, well-maintained UK primary care database, The Health Improvement Network (http://www.epic-uk.org/our-data/our-data.shtml). People with intellectual disability (n=33 016) were identified using a comprehensive set of diagnostic codes. Neuropsychiatric outcomes of interest were examined by individually examining and coding de-identified records. In addition, challenging behaviour was identified using standardised clinical codes within the database and prescription of psychotropic drugs was classified according to standardised categories. Multivariate mixed Poisson regression was used to examine trends and factors associated with challenging behaviour and psychotropic prescription.

What this paper add

• This is the most comprehensive study of the prevalence of mental disorders and psychotropic prescribing patterns in a representative primary care sample of adults with intellectual disability.

• This study confirms high rates of severe mental illness in people with intellectual disability (32/10 000 person years). Other mental disorders such as depression and anxiety were not over-represented in people with intellectual disability, raising the possibility that these conditions are under-recognised in this group.

• The study finds that challenging behaviour is more common than previously noted, occurring in about one-third of people with intellectual disability. It was more common in those with profound compared with mild intellectual disability (incidence rate ratio (IRR) 2.97, 95% CI 2.09 to 4.21), in those with autism (IRR 1.83, 1.64 to 2.03), in those with severe mental illness (IRR 1.69, 1.53 to 1.88), and in those with dementia (IRR 1.71, 1.45 to 2.01). Even after controlling for dementia, older age was independently associated with challenging behaviour, raising questions about a possible under-recognition of dementia in people with intellectual disability.

• Almost two-thirds of the cohort had a history of psychotropic prescription by the end of the study period. Antipsychotic prescription rates in people with intellectual disability (132/10 000 person years) were double that of the general population. Further, in 71% of cases antipsychotics were prescribed to people with no record of severe mental illness, and in 26% of cases in which antipsychotics were prescribed there was no record of severe mental illness or challenging behaviour.

Limitations

• Results may be influenced by the under-representation of people with less-severe disability.

• The accuracy of diagnostic coding within the database cannot be established with reference to standardised clinical diagnoses.

• The underlying indication for prescription is unavailable, so unnecessary prescribing is by inference only.

What next in research

Improving the mental health and well-being of people with intellectual disability requires an effective, equipped and skilled primary care workforce. Results from this study suggest that GPs require continuing professional support, skills development and education in this area. They also highlight the importance of timely access to specialist and behavioural support and the need for review of prescribing, particularly where antipsychotic medication is being considered for a non-primary indication. Future generations of doctors in training should undertake mandatory training that addresses the rights and healthcare needs of people with intellectual and developmental disabilities.

Do these results change your practices and why?

Yes, this study has practical implications for most jurisdictions internationally. Given the health and behavioural complexities in people with intellectual disability, GPs should be supported to practice in a multidisciplinary framework that values appropriate behavioural and psychological interventions. This requires practical and administrative adjustments which incentivise long consultations with individuals, and encourage effective communication with the person and others involved in supporting their access to mental health, behavioural and social supports.3 In many jurisdictions access to specialist psychiatrists with specific expertise in intellectual and developmental disabilities is limited. The development of enhanced specialist capacity and clinical pathways, particularly between primary and specialist care is required. Without such specialist backup, effective mental healthcare in general practice is very difficult.