The American Association on Intellectual and Developmental Disabilities defines intellectual disability (ID) specifically as a disability originating before the age of 18 and characterized by significant limitations both in intellectual functioning and in adaptive behavior.1,2 Intellectual disabilities are included in the umbrella terminology of “developmental disabilities” that also includes many other disabilities recognized during childhood, such as cerebral palsy, autistic spectrum disorders (ASD), and epilepsy.2,3 “Intellectual Disability” is currently the preferred terminology and includes the same group of individuals diagnosed previously with “Mental Retardation”, which is no longer used internationally or in the U.S. federal legislation.2,4 Several of the authors this month still use the term “mental retardation” to accurately and consistently characterize patients that were included in studies conducted before this change in name. The definition of “mental retardation” to focus on an individual's failure to adapt socially has changed in the past several decades to now reflect the current understanding of “intellectual disability” to be a condition potentially enhanced by various support mechanisms, rather than a unchanging, lifelong disability.2 To assess and define intellectual disabilities, practitioners should evaluate both intellectual functioning and adaptive behavior.2 The IQ test is an important tool used in the assessment of intellectual functioning, however, it should not be used as the sole measure to diagnose, define, or assess intellectual disability.2,4 Several important points are noted in the rationale to remove the IQ test from the diagnostic criteria in the Diagnostic and Statistical Manual of Mental Disorders-5 (DSM-5) (see Table 1), including that the diagnosis of ID is based on clinical assessment as well as standardized testing of intelligence, that the definition of intelligence encompasses general mental ability that involves various domains including reasoning, problem solving, thinking abstractly, comprehending ideas, and judgment, and that cognitive profiles (which may include sociocultural background, native language, etc.) are more useful for characterizing intellectual disabilities than a single number.4 Additionally, to assess adaptive behavior, tests to evaluate conceptual skills (e.g. language and literacy, money, time, etc.), social skills (e.g. interpersonal skills, social responsibility, self-esteem, ability to follow rules, etc.), and practical skills are used (e.g. activities of daily living, occupational skills, schedules/routines, etc.).2 

Table 1:

Proposed DSM-5 vs. DSM-IV-TR4 

Proposed DSM-5 vs. DSM-IV-TR4
Proposed DSM-5 vs. DSM-IV-TR4

Stereotypies and challenging behaviors are often present in individuals with intellectual disabilities.5 There are many synonyms or descriptions for describing “challenging behavior(s)” or a behavior or behavioral syndromes associated with lack of control including but not limited to the following: “disruptive behavior”, “aggression”, “aggression-related behavior”, “impulsive behavior”, “ impulse control disorder”, “ maladaptive behavior”, “ externalizing behavior”, or “ self-injurious behavior”.6 Patients with ID are also 4 to 5 times more likely to suffer from comorbid psychopathologies (defined as disorders identified in the DSM-IV-Text Revision and ICD-10) compared to the general population.7 Autism, self-injurious behavior, ADHD, anxiety, depression, and psychosis are particularly common comorbidities.7 There appears to be genetic and neurodevelopmental overlap between ID and ASD.5 Individuals with co-occurring ID and ASD have a poor prognosis and it appears that the lower the IQ in an individual with autism, the higher the rates of stereotypies and challenging behaviors, including self-injury.5 Patients with both ID and ASD appear to be at higher risk for psychiatric comorbidities.5 

Habler et al. notes that disruptive and/or self-injurious behavior occurs in 10–62% of institutionalized individuals with ID.6 Of note, aggressive behaviors towards self, others, and objects reported in 30–60% of individuals with ID represent the core of challenging behaviors.8 Aggressive behaviors are a significant issue because they pose a potential threat to personal safety and the safety of others and they interfere with the education and socialization of individuals with ID via exclusion from schools and community activities.8 Additionally, aggressive behaviors may lead to institutionalization as well as referrals for behavioral and psychiatric intervention and ultimately have consequences on the quality of life of an individual with ID.3.8 In order to change the behaviors, effective interventions must occur early because aggression in individuals with developmental disabilities is a learned behavior where the aggression achieves a desired outcome or is functionally related to the consequences that follow (which may be perceived as a positive outcome by the individual, e.g. being escorted out of group activities for threatening another individual).3 

Individuals with ID are among the most medicated population in society.7 Pharmacotherapy may have a role in those with co-occurring psychiatric illnesses, however it appears to have a limited role in addressing challenging behaviors, which tend to be independent of psychopathology and mostly caused by environmental variables (e.g. efforts to gain attention, edibles, escape from undesirable activities, etc.).7 Treatment of challenging behaviors has transitioned from the use of mechanical and chemical restraint to the use of psychological treatments, such as social and coping skills treatment, cognitive behavioral therapy, and noncontingent reinforcement.7 The key feature of psychological treatment, however, is functional assessment, where the purpose is to identify potential environmental causes and what factors maintain the challenging behaviors.7 The best evidence for psychological treatments is focused more on challenging behaviors that occur in individuals with ID, rather than for the treatment of core symptoms of psychiatric comorbidities.7 There is a paucity of studies evaluating intervention “packages” containing both pharmacotherapy and behavioral treatments and similarly, there is a lack of studies comparing various interventions in a controlled setting.7 

Individuals with intellectual and developmental disabilities represent a population with potentially difficult and highly complex medication regimens. This issue of the Mental Health Clinician (MHC) is dedicated to helping readers become more familiar with the role of psychotropics in intellectual and developmental disabilities, highlighting treatment considerations and issues. Subsequently, case reports will detail potentially paradoxical reactions to medications and highlight therapeutic options for patients with developmental disabilities. The evidence behind the use of antipsychotics and psychostimulants for challenging behaviors in individuals with intellectual disabilities and the use of naltrexone for self-injurious behaviors will be reviewed. The name, definition, and focus of treatment with regards to intellectual disabilities have changed over time – the September 2012 MHC issue is devoted to analyzing just a small aspect of the current treatment of targeted behaviors in these individuals.

1.
American Association on Intellectual and Developmental Disabilities
.
Definition of Intellectual Disability
.
Accessed from http://www.aamr.org/content_100.cfm?navID=21 on August 2, 2012
.
2.
American Association on Intellectual and Developmental Disabilities
.
FAQ on Intellectual Disability
.
Accessed from http://www.aamr.org/content_104.cfm?navID=22 on August 2, 2012
.
3.
Brosnan
J
,
Healy
O
.
A review of behavioral interventions for the treatment of aggression in individuals with developmental disabilities
.
Res Dev Disabil
.
2011
;
32
(
2
):
437
46
. .
4.
American Psychiatric Association DSM-5 Development
.
Proposed Revision: A 00 Intellectual Developmental Disorder
. .
5.
Matson
JL
,
Shoemaker
M
.
Intellectual disability and its relationship to autism spectrum disorders
.
Res Dev Disabil
.
2009
;
30
(
6
):
1107
14
. .
6.
Hässler
F
,
Reis
O.
Pharmacotherapy of disruptive behavior in mentally retarded subjects: A review of the current literature
.
Dev Disabil Res Rev
.
2010
;
16
(
3
):
265
72
.
DOI: 10.1002/ddrr.119. PubMed PMID: 20981765
.
7.
Matson
JL
,
Shoemaker
ME
.
Psychopathology and intellectual disability
.
Curr Opin Psychiatry
.
2011
;
24
(
5
):
367
71
. .
8.
Tsiouris
JA
,
Kim
SY
,
Brown
WT
,
Cohen
IL
.
Association of aggressive behaviours with psychiatric disorders, age, sex and degree of intellectual disability: a large-scale survey
.
J Intellect Disabil Res
.
2011
;
55
(
7
):
636
49
. .