Dual diagnosis does not essentially mean the co-occurrence of a mental illness and substance abuse: it extends much further. The term can also be used to define the compounding and “diagnostically-overshadowed” co-morbidity of mental illness and intellectual disability (ID).
This population of individuals is seldom recognized as they battle on their own with a co-occurring intellectual disability, previously known as mental retardation, and a mental illness. Mental retardation is a condition diagnosed usually in infancy reflecting a lower than average function of the intellect and a lack of skills necessary for daily operation. A mental illness, on the other hand, influences a person’s thinking, feeling or mood, affecting the ability to relate to others and daily functioning. It is concerning as to how only a few specialists are trained in and aware of this co-occurring condition that transpires more frequently than often realized.
The intellectually disabled have often been unable to get the required treatment because their co-occurring mental illness has also been subjected under the context of their disability. The common misconception prevailed that it was not possible for people with cognitive disabilities to have a mental illness. They were not even considered to be able to have the same feelings as the typical population. This “diagnostic overshadowing,” letting the intellectual disability diagnosis block recognition of mental illness, still prevails. Even when a person with ID acts uncharacteristically or dangerously, it is often misconstrued as disruptive behavior and not as symptoms of an undiagnosed mental illness.
There have been very few studies that focused on psychotherapeutic interventions in the intellectually disabled patient. In 1982, Reiss, et al. hypothesized that intellectual subnormality is such a primary feature of a patient that it sidelines other existing emotional disturbances. He introduced the term diagnostic overshadowing to describe the failure of recognizing and treating the emotional and behavioral expressions of mental illness in a developmentally disabled person.
The prevalence of mental illnesses in the intellectually disabled population is conservatively estimated to be 33 percent while some sources have reported significantly higher rates. The intellectually disabled are considered more susceptible to mental illnesses due to their unique biological and social dispositions. The more it is being discovered that mental illnesses are initiated or aggravated by biochemical alterations, the more chances exist for an already-damaged brain to be at a higher risk of biochemical imbalances.
Some disorders are largely caused by psychological factors, particularly because of a prolonged exposure to adverse social conditions. The negative attitudes towards people with mental retardation may give way to the development of mental illnesses.
Unfortunately, a main reason for higher statistical figures was the absence of dual diagnosis from the training curriculum of standard clinical graduate programs and medical schools. This situation was further compounded by the limited communication skills of people with ID. According to Silka and Hauser, consequentially, it becomes even more difficult, or in some cases impossible, for the intellectually disabled to relay their experiences accurately to a professional.
Furthermore, owing to limited social exposure and cognitive limitations, such individuals might not even be able to distinguish whether what they are feeling is even normal.
Silka and Hauser further note that people with ID often experience fluctuations in their already-existing behavior anomalies such as hand flapping. Such factors are routinely mistaken for learned behaviors characteristic to developmental delays and not considered as possible symptoms of an emerging mental illness.
The National Association for the Dually Diagnosed published the Diagnostic Manual-Intellectual Disability (DM-ID): A Textbook of Diagnosis of Mental Disorders in Persons with Intellectual Disability in 2013, allowing clinicians to have a reliable resource guide to assist with the assessment and treatment of this dual diagnosis. For experienced clinicians, the book provided a standardized set of diagnostic criteria that will facilitate communication and treatment.
As a result of the mutual effort of NADD and the American Psychiatric Association (APA), the volume was 10 years in the making. Using the DSM-IV-TR categories of mental illness, panels of experts worked to describe how symptoms are expressed by those who often can’t adequately report their experience.
Even though the last couple of decades have witnessed significant progress in the field of mental illness, the adaptation of this progress has been rather slow when it comes to intellectual disability. There is still a significant necessity for community services and support systems for people battling both mental illness and intellectual disability.
Dual diagnosis, even though highly complex, is treatable. The Dual Diagnosis Helpline is available to help you or a loved one at any time. We understand the complexities of co-occurring conditions and can connect you to a treatment provider who is able to serve your needs. Do not hesitate to call us right away at any time