Intellectual disability (ID) is the term used to define a developmental disorder characterized by both intellectual and adaptive functioning deficits. This term has replaced “mental retardation” in DSM-5, which was spearheaded by the renaming of organizations such as the President’s Committee for People With Intellectual Disabilities in 2003 and the American Association on Intellectual and Developmental Disabilities in 2006. This terminology shift presents a welcome change from the negative perception of mental retardation in the general population and the medical community. In fact, the American Medical Association has instituted a policy to support the classification of individuals with ID as a medically underserved population. Also, the Commission to End Health Care Disparities expanded the scope of the commission to include persons with ID.
The prevalence of psychiatric disorders is higher in patients with ID. And psychiatric disorders in this population are typically more severe and more difficult to diagnose than in the general population; the degree of disability varies greatly. In the past 25 years, care has shifted from state hospitals to the community setting, thus increasing the need for medical and psychiatric care in the community. However, adequate services are typically lacking and the specific training of medical and psychiatric professionals is often insufficient. This has created additional barriers to proper intervention and treatment. In a survey by Werner and colleagues,1 90.2% of psychiatrists felt they lacked specific training in treating and diagnosing problems in the ID population.
What new information does this article provide?
The purpose of this article is to increase awareness of the varied and atypical presentations of patients with intellectual disabilities and comorbid psychiatric illnesses. Novel approaches to behavioral therapy and environmental modifications, and a review of pharmacotherapeutic options are discussed.
What are the implications for psychiatric practice?
The aim of this article is to assist practitioners by providing tips for diagnosing and treating patients with intellectual disabilities and comorbid mental illness. Relevant cases are provided to highlight the inherent complexities of this underserved community and to give insight to clinicians regarding multimodal treatment options.
Prevalence of psychiatric problems
The prevalence of psychiatric disorders in individuals with ID is estimated to be between 32% and 40% (Table 1).2 Psychiatric disorders are more easily diagnosed in patients with mild to moderate ID than in those with severe ID.
The prevalence of autism spectrum disorders in individuals with mild ID is 5% to 10%, and in those with moderate to severe ID, up to 30%.3 The prevalence of ADHD in children with ID is estimated to be between 8.7% and 16%, compared with 5% in the general population.4 The prevalence of MDD has been reported to be 1.5- to 2-fold higher than that in the general population, while rates of both schizophrenia and bipolar disorder have been estimated at twice that in the general population.3 High rates of anxiety disorders have also been reported in this population, particularly in those with comorbid autism with symptoms of phobias, stereotypies, and compulsions.5
Challenging behaviors (ie, aggression toward others; self-injurious behavior; inappropriate social and sexual behavior; and selfstimulating behavior, such as rocking, withdrawal, or noncompliance) are 3 to 5 times more common in the ID population.6 About 12% to 46% of individuals who have ID receive psychotropics for such behavioral problems. Rates are higher among adults and those living in institutions.4
Findings suggest that certain behavioral problems are associated with specific psychiatric diagnoses.7 Anxiety has been correlated with tantrums, mania with tantrums, aggression, and screaming; depression has been correlated with aggression, tantrums, and screaming in severe/profound ID and with tantrums and self-injury in mild to moderate ID.
Dr Aggarwal is an Assistant Professor in the department of psychiatry at Rutgers New Jersey Medical School, Newark. Dr Guanci is PGY-4 Resident in the department of psychiatry at Rutgers New Jersey Medical School. Dr Appareddy is Immediate Past Chair of the AMA IMG Governing Council and Vice Chair of the President’s Committee for People With Intellectual Disabilities (2002-2006). They report no conflicts of interest concerning the subject matter of this article.
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