The term developmental disability encompasses a number of conditions including cognitive disabilities (i.e., mental retardation), autism, cerebral palsy, epilepsy, brain injury, and spina bifida. A developmental disability is a severe, disabling condition that arises in infancy or childhood, persists indefinitely, and causes serious problems in language, learning, mobility, and the capacity for independent living (New Jersey Developmental Disabilities Council, 1997/1998, p. 1).
Since the mid-1800s, when the first segregated schools were developed for children with mental retardation, most people with severe developmental disabilities have been institutionalized for most of their lives. The first segregated schools were designed to be small, personal, individualized, and temporary, offering services designed to develop the skills necessary for success in the community. Segregated schools quickly became large institutions designed to "protect" society from children with retardation who might grow up to be depraved and dangerous adults (Mauch, 1991, p. 3). In a further attempt to "protect" society, the eugenics movement, begun at the turn of the century, encouraged the sterilization of people with developmental disabilities.
During the 1950s, parents of people with developmental disabilities began to demand a greater focus on educational and developmental approaches to services. The idea of institutions as the only service option was rejected and some parents began to keep their children with developmental disabilities at home. Parental organizations such as the Association for Retarded Children (ARC) emerged. ARC, which later changed its name to the Association for Retarded Citizens and more recently became simply The Arc (Roberts, 1996), became strong advocates for family members. During the 1960s and 1970s, litigation and advocacy led to the establishment of rights for people with developmental disabilities, such as public education and services in the least restricted environment (Mauch, 1991). The work of many people such as Wolfensberger, who articulated the principle of normalization (discussed in Chapter 4), and Marc Gold, who demonstrated that people with the most severe cognitive disabilities could learn complex skills, fueled the growing dissatisfaction with institutional care. These new ideas about the rights and abilities of people with disabilities ultimately led to the development of supported employment (discussed in Chapter 9) and other community-based supports for people with developmental disabilities. During the last few decades, we have seen the downsizing and closing of state institutions as more and more people with developmental disabilities are being supported in their efforts to live, learn, work, and socialize in the community (Mauch, 1991; Schwartz, 1992; Torrey, 1993).
Incidence of Mental Illness and Developmental Disability
Studies of people with developmental disabilities living in the community suggest that among these individuals 20% to 35% experience a coexisting mental illness (Parsons,
May, & Menolascino, 1984; Torrey, 1993). However, Parsons and colleagues caution that these studies include many children under the age of 12 and, therefore, should not be considered a true reflection of incidence among adults. More recently, Szymanski et al. (1998) reported an incidence rate for schizophrenia, other psychotic disorders, and mood disorders among people with developmental disabilities that is similar to that found in the general public. They further reported that the incidence of personality disorders, among people with developmental disabilities, appears to be higher than usual, but suggested that this may be "related to maladaptive personality traits resulting from negative social experiences" (p. 14). Furthermore, the full range of mental illnesses has been identified among people with developmental disabilities (Torrey, 1993).
Diagnosing mental illness in a person with a developmental disability can be a difficult task. The diagnostic process includes self-report of thoughts, feelings, and symptoms. For individuals with significant communication impairments, this may be difficult, if not impossible. Often, in these situations, a diagnosis is based on reported behavior such as an increase in aggression, self-injury, tearfulness, and withdrawal. These same behaviors, can also be indications of physical illness, psychological stress, or dissatisfaction (Stark, McGee, Menolascino, Baker, & Menousek, 1984; Torrey, 1993).
The potential for misdiagnosis is clearly great. A misdiagnosis brings with it the possibly unnecessary or incorrect use of medication, which is of great concern to people with disabilities, their families, and advocates.
Individuals with developmental disabilities and mental illness have great difficulty receiving adequate services. Often the services that are available are provided by different systems that are funded by different sources. Programs designed for mental illness often consider individuals with a dual diagnosis to have mental retardation as the primary diagnosis, and programs designed for developmental disorders often consider persons with a dual diagnosis to have a mental illness as the primary diagnosis. PsyR practitioners have to make an effort to work across programs, with people from different disciplines and programs.
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