Higher Incidence of Mania in Adults With Intellectual Disabilities vs General Population

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Depression has a similar incidence in adults with intellectual disabilities compared with the general population.
Depression has a similar incidence in adults with intellectual disabilities compared with the general population.

Depression in adults with intellectual disabilities is more enduring than in the general population, despite high use of mood stabilizers, and this also is a high-risk group for mania, according to the results of a prospective cohort study published in the British Journal of Psychiatry.

Sally-Ann Cooper, MB, MD, FRCPsych, from the Institute of Health and Wellbeing, University of Glasgow, Mental Health and Wellbeing Group, Gartnavel Royal Hospital, Glasgow, Scotland, and colleagues investigated affective disorder incidence and determinants of unipolar depression in adults with mild to profound intellectual disabilities.

The investigators followed 651 adults during a 2-year period. Although 22.4% of patients were using mood stabilizers, the 2-year incidence of mania was 1.1%, which is higher than in the general population, and 0.3% for first episode (standardized incident ratio [SIR], 41.5; when excluding Down syndrome, SIR, 52.7). For any bipolar episode, the SIR was 2.0 (or 2.5 excluding Down syndrome).

The incidence of depression was 7.2%, which is similar to the general population (SIR, 1.2), but depression is more prevalent in this population, suggesting it is more enduring and undertreated. Problem behaviors (odds ratio [OR], 2.3) and life events (OR, 1.3) predict incident unipolar depression.

The finding of a high incidence of mania is surprising, given that many of these patients were prescribed mood stabilizers, in most cases for epilepsy. The authors argue that clinicians should have a heightened awareness of this and treat depression thoroughly in these patients. Furthermore, they should consider mania in their differential diagnosis, as there is the potential for misdiagnosis with attention-deficit/hyperactivity disorder and problem behaviors that are common in adults with intellectual disabilities.

The authors suggest that future study design should include more person-years and that there should be further investigation into causation and interventions for depression in individuals with intellectual disabilities.

Reference

Cooper SA, Smiley E, Allan L, Morrison J. Incidence of unipolar and bipolar depression, and mania in adults with intellectual disabilities: prospective cohort study [published online March 15, 2018]. Br J Psychiatry. doi: 10.1192/bjp.2018.12

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