IDD/MI Diagnosis

What is an IDD/MI Dual Diagnosis?

An IDD/MI dual diagnos refers to individuals with an intellectual/developmental disability (IDD) who concurrently experience a mental health condition. While the exact prevalence is unknown, most professionals accept that roughly 35% of people with intellectual disabilities also experience mental health challenges.

Intellectual vs. Developmental Disabilities

The American Psychiatric Association defines intellectual disability as a disorder with onset occurring in childhood prior to 18 years old that includes both intellectual and adaptive functioning deficits in conceptual, social, and practical domains (DSM-5, 2013).  Intellectual abilities are measured through an IQ test.  However, severity of ID is determined by adaptive scores – mild, moderate, severe, profound.  Adaptive scores assess abilities related to activities of daily living, such as dressing, personal hygiene, feeding, communicating, etc.

The federal definition of developmental disabilities is not limited to intellectual disabilities and is based on functional criteria.  The Developmental Disabilities Act (2000) defines developmental disability as a severe, chronic disability of an individual that:

  • Is attributable to a mental or physical impairment or combination of mental and physical impairments;
  • Is manifested before the individual attains age 22;
  • Is likely to continue indefinitely; 
  • Results in the substantial functional limitations in 3 or more of the following areas of major life activity:
    • Self-Care
    • Receptive and expressive language
    • Learning
    • Mobility
    • Self-direction
    • Capacity for Independent living
    • Self-direction
    • Economic self-sufficiency; and
  • Reflects the individual’s need for a combination and sequence of special, interdisciplinary, or generic services, individualized supports, or other forms of assistance that are of lifelong or extended duration and are individually planned and coordinated.

Mental Health Conditions

It is important to note that, like everyone else people with intellectual and developmental disabilities experience the full range of human emotions and conditions that exist, including life’s joys and challenges and the full spectrum of mental health conditions.

Mental health conditions refer to severe disturbances in behavior, mood, thought processes, and/or interpersonal relationships.  There are various types of mental health conditions listed in the DSM-5 published in 2013.  Below are a few of the most common mental health conditions:

  • Schizophrenia spectrum disorder and other psychotic disorders
  • Bipolar and related disorders
  • Depressive disorders 
  • Anxiety disorders
  • Obsessive-compulsive and related disorders
  • Trauma- and stressor-related disorders
  • Dissociative disorders

Dual Diagnoses

While not a new concept, the co-occurrence of IDD and mental health conditions has been receiving more attention in recent years.  The publication of the DM-ID and the DM-ID-2 have been instrumental in the recognition of mental health conditions in individuals with intellectual and developmental disabilities.  When an individual has cognitive and communication challenges, clinicians may find diagnosis challenging. The DM-ID-2 provides clinicians with the ability to recognize and diagnose co-occurring conditions.  With accurate diagnoses, treatment supports will more accurately match the needs of the person being supported.

The biopsychosocial approach has been used in the medical community for decades and is emerging as a promising practice in the behavioral health community.  The biopsychosocial approach is a whole person approach to supporting patients to address all potential areas that may impact a person’s response to treatments.  Bio refers to the biological considerations including physical health, genetics, medical conditions, medications, and so on.  Psycho refers to the psychiatric and psychological needs of a patient including mental wellness, psychiatric diagnoses, mood, developmental stages, intellectual abilities, cognitive wellbeing, and the like.  Social refers to the social determinants of health – natural supports, friends, families, finances, transportation, linkage to community resources, food disparities, and jobs.  Each of these factors combines to affect how a person responds to treatments for any given area of need.  If a person does not have a secure place to live (social), then their response to habilitative or mental health supports (psycho) will likely be hindered.