PSYCHIATRIC AND MENTAL DISORDERS IN AGING ADULTS WITH MENTAL RETARDATION
Mental retardation continues to be a widely used term to describe the condition of subaverage intellectual function in the presence of deficits in adaptive behavior. Critics have attacked this definition for a variety of reasons. These include reliance on intelligence tests to demonstrate intellectual difficulties, which has been criticized because of difficulties in determining cut-off values for normality, the questionable cultural fairness of the tests, and the questionable relevance of the tests for performance in real-life situations. Similar controversies regarding the imprecision of definition and measurement of adaptive behavior remain unresolved. However, the key concept of a central, biologically based deficit in intellectual function appears to be valid; persons with mental retardation have a condition in which nearly every cognitive process that has been studied is deficient. For mild mental retardation, the same genetic and environmental influences appear to operate that determine individual differences throughout the normal range of variation in general cognitive ability. Importantly, the heritability of general cognitive ability is substantial, probably around 50%; the effects of shared environmental influences in families become negligible after adolescence, and genetic influence increases from infancy to adulthood. Persons with severe degrees of mental retardation are more likely to have structural defects of the brain or metabolic or chromosomal derangements. The challenge for the future is to determine how these biologic abnormalities interact with the aging process.
The number of aging persons with mental retardation is increasing, probably because of increased longevity. Life expectancy in mental retardation has increased from 20 years in the 1930s to 60 years in 1980. For those with Down syndrome, life expectancy has increased by about 30 years. The prevalence of mental retardation and developmental disability (cerebral palsy, autism, epilepsy) is generally assumed to be around 1%. Thus, estimates are that in the United States there are 525,000 persons aged 60 and over with these conditions, and the numbers are expected to double by 2030.
The prevalence of psychiatric disorders among adults with mental retardation is about five times that of age-matched control groups. Depending on the exact population studied and the type of diagnoses included, rates range from 10% to 40%.
Adults with Down syndrome have an increased risk for the early onset of Alzheimer’s disease, with nearly 100% developing the neuropathology by age 40. Although not all develop symptoms in their 40s, approximately 40% aged 50 and over have symptoms of dementia, with 50% developing seizures as a result of the degenerative changes. Approximately 75% of persons with Down syndrome in their 60s have symptoms of dementia (compared with a prevalence in the general population of 5% at age 65). Symptoms also include loss of adaptive skills and increased maladaptive behavior; the dementia is often associated with depression, indifference, and social inappropriateness. The average age at death for persons with Down syndrome and Alzheimer’s disease is approximately 50. One study has demonstrated that in women with Down syndrome, an early age of menopause is associated with earlier dementia symptoms. Menopause may be an important factor among women with mental retardation who experience a behavioral or cognitive change in late life.
The incidence of dementia in persons with mental retardation who do not have Down syndrome is the same as in the general population; however, these persons also have a higher prevalence of the neuropathology of Alzheimer’s disease: 54% for ages 50 to 65, 76% for ages 66 to 75, 87% for ages > 75.
For persons with mental retardation, the lifetime prevalence of other major mental illnesses appears to be similar to or slightly higher than that of the general population. In those aged 65 and over, approximately 70% may reach criteria for a psychiatric diagnosis, often with higher rates than for a younger age group. Autistic traits are common, occurring in up to approximately half of adults with learning disability or mental retardation. These traits are more common in those with severe or profound degrees of mental retardation and in younger individuals; they are typically associated with behavioral difficulties.
Difficulties that adults with mental retardation have with adaptive behavior may be severe, and difficulties may occur with increasing frequency in later life as a consequence of cognitive decline and increasingly impaired mobility. For example, surveys concerning adults with mental retardation have revealed that 25% have no useful speech and 10% have no receptive comprehension. Half do not have basic self-care skills, half have a physical disability, and half have a mobility impairment; 10% are totally dependent. Support services for these people are usually deficient.
As many as 50% to 60% of adults with mental retardation have a maladaptive behavior (such as withdrawal, self-injury, stereotypy) that is severe or that occurs frequently, and follow-up studies show that these behaviors may persist for years. The proportion decreases with age, except in Down syndrome, in which the proportion is higher and the incidence of behavioral problems increases with the degree of mental retardation. Aggression occurs with similar frequency in all age groups. About half of the persons with behavioral disorders have
The diagnosis of a mental disorder in the older adult with mental retardation is based on the same principles of history and examination that apply in the general population. However, presentations of mental illness may be different in these patients. Typically, verbal skills are poor, and reports of mood or mental experiences are difficult to obtain. Often, mental disorders present as behavioral changes, for example, social withdrawal, apathy, and vegetative changes occurring in depressed persons, or agitation, sleeplessness, or aggression in those experiencing delusions or hallucinations. It is more difficult for persons with limited coping skills to adjust to changes in living or work situations, and inquiries should be made about whether such changes have occurred.
It is important to identify the cause of the person’s mental retardation. Careful physical, laboratory, and neurologic investigation (electroencephalography and neuroimaging) may establish a cause in 40%. Different conditions are associated with different problems (see Table 40.1). Medical disorders commonly present as psychiatric or behavioral disorders, and they occur in persons with mental retardation twice as commonly as in the average psychiatric population.
Maladaptive behaviors, such as aggression, are common in persons with mental retardation and may not indicate a mental disorder. An impulsive response to a stressor may reflect only suboptimal judgment in a particular situation. An appropriate treatment in such cases would be instructional or behavioral; the preferred behavior programs are ones that reward good behavior. A disorder of impulse control, however, may also produce aggressive responses; diagnosis of such a disorder requires a pattern of impulsivity that is disproportionate to the degree of intellectual impairment. With an impulse-control disorder, aggression may be preceded by a period of increasing tension and arousal, occur explosively and out of proportion to the stressor, and seem to have a driven, sustained nature. Appropriate treatment would consist of instructional and behavioral methods, but also with pharmacologic interventions to reduce impulsivity (eg, selective serotonin-reuptake inhibitorsOL) or arousal (eg, β-blockersOL). Pharmacologic treatment of aggression is similar to that in the general population and includes the use of mood stabilizersOL, selective serotonin-reuptake inhibitorsOL, β-blockersOL, and antipsychotic medicationsOL.
The diagnosis of dementia among persons with mental retardation is made according to the same criteria as in the general population. These criteria include the presence of cognitive and adaptive deterioration; demonstration of deficits on examination (preferably with longitudinal follow-up showing progression of deficits); and exclusion of other possible causes of deterioration, such as medical or environmental factors, or other mental disorders, such as depression or delirium. Standardized scales are available that help structure the interview and history and produce a score that indicates the likelihood that dementia is present and its severity. The Washington University Clinical Dementia Rating Scale that is widely used with the general population can also be used in many individuals with mental retardation. Neuroimaging studies may be helpful in establishing the diagnosis and in differentiating Alzheimer’s disease from vascular dementia; longitudinal and volumetric studies may help differentiate normal aging from dementia. There are insufficient studies to demonstrate the efficacy of standard treatments (such as donepezil) in persons with mental retardation.
Adults with mental retardation have more medical problems than do age-matched persons (approximately five medical conditions per person; those with more severe mental retardation have more problems). Approximately two thirds of those in a community setting have chronic conditions or major physical disability. It is estimated that 50% of these medical conditions go undetected. Prompt detection and treatment is associated with better survival. Visual or hearing impairments are more common in persons with mental retardation; they increase with age and affect approximately 25%.
Persons with Down syndrome and others with mental retardation have similar age-specific mortality until ages 30 to 34, after which there is an exponential increase in mortality with age for those with Down syndrome, probably because of the onset of dementia. Life expectancy decreases with increasing severity of mental retardation, and with other morbidity such as inability to ambulate, lack of feeding skills, and incontinence. Life expectancy for adults with mental retardation is lower than for the general population and is about 65 years. The commonest causes of death are cardiovascular and respiratory disorders, cancer, and dementia (particularly in Down syndrome).
At least 80% of adults with mental retardation live at home and are cared for by aging family members; 20% live in residential programs. It is estimated that about 40% of eligible persons may not be served by the formal service system. This situation often leads to a crisis when the parent is no longer able to provide adequate care or is unable to manage a behavioral problem. It is estimated that about half of developmentally disabled adults with a behavior problem need a different living arrangement. Typically, more than half of the families have not made plans for the future care of adult relatives with mental retardation; those in day programs or workshops do not typically have pensions or Social Security benefits to allow retirement. Not surprisingly, the degree of mental retardation, physical health, and functional skills of the aging person correlate with the degree of parental stress and burden, although maternal and family characteristics such as education and income are more correlated with overall life satisfaction and maternal well-being.
■ Eastgate G, Lennox NG. Primary health care for adults with intellectual disability. Aust Fam Physician. 2003;32(5):330–333.
This article addresses the clinical challenges in managing adults with intellectual disability. These persons commonly have undiagnosed health problems, and treatment may require a specialized approach to overcome deficits in communication. This article outlines the common physical and psychiatric conditions found in adults with intellectual disability and highlights the need for a structured approach to health care for patients with limited communication skills. An overview of strategies for better assessment and management for older adults with developmental disabilities is provided.
■ Gedye A. The Dementia Scale for Down Syndrome. Vancouver, BC, Canada: Gedye Research and Consulting; 1995. (To order, contact A. Gedye, Gedye Research and Consulting, PO Box 39081, Point Grey, Vancouver, BC, Canada V6R 4P1. Phone/Fax: 604-733-1950.)
This scale assesses the presence or absence of dementia in adults with Down syndrome; it has also been used for the same purpose in mentally retarded persons who do not have Down syndrome. Information is collected from caregivers only. Field testing has demonstrated a concurrent validity coefficient (kappa) of 0.81 and an inter-rater reliability kappa coefficient of 0.91. Diagnosis with the scale was compared with diagnosis by clinicians (see Deb S, Braganza J. Comparison of rating scales for the diagnosis of dementia in adults with Down’s syndrome. J Intellect Disabil Res.1999;43 [part 50]:400–407), and a sensitivity of 0.85 and specificity of 0.89 for the scale were found.
■ Ryan R, Sunada K. Medical evaluation of persons with mental retardation referred for psychiatric assessment. Gen Hosp Psychiatry. 1997;19(4):274–280.
A total of 1135 people with mental retardation referred for mental health assessment for a behavioral deterioration were medically evaluated by a two-step protocol that involved a screening evaluation plus expanded testing, depending on clinical findings. Medical comorbidity was double that of similar persons without mental retardation, and 75% had one or more medical problems, almost all undiagnosed or undertreated. In 258 patients, treatment of the medical condition caused remission of the psychiatric condition.
■ Sutherland G, Couch MA, Iacono T. Health issues for adults with developmental disability. Res Dev Disabil. 2002;23(6):422–445.
This paper highlights the specific health concerns found in adults with developmental disabilities and reviews the most common untreated conditions that may be recognized with special attention. Other environmental factors that are important in the clinical management of adults with mental retardation are also addressed, including the impact of living arrangements and caregivers on health-promoting activities. The complexity of the interactions among biology, pathology, and behavioral and environmental determinants for the disabled individual are discussed. Greater use of self-reported health studies is suggested, as well as further exploration of effective strategies of health promotion for this population.
Andrew C. Warren, MB, BS, DPhil