Neurodevelopmental Disorders (Intellectual Disabilities including Autism)

What is an intellectual disability?

An intellectual disability is a disability characterized by significant limitations in both intellectual functioning (reasoning, learning, and problem solving) and in adaptive behavior (conceptual, social, and practical skills) that emerges before the age of 18. The American Association on Intellectual and Developmental Disabilities views intellectual disability as a functional interaction between an individual and the environment, rather than a static designation of a person’s limitations.

Degrees of intellectual disability are diagnosed as mild, moderate, severe, and profound. Approximately 85 percent of individuals with an intellectual disability fall into the mild category.

What are the different levels of intellectual disability that can occur in children and adults?

In preschool age children (up to 5 years old), intellectual disability is classified at one of the following levels:

  • The child can develop social and communication skills. There is minimal retardation in sensorimotor areas.
  • The child can talk or learn to communicate but has poor social awareness and fair motor development. The child benefits from self-help training and can be managed with moderate supervision.
  • The child has poor motor development with minimal speech and little or no communication skills. The child is generally unable to benefit from self-help training.
  • The child has minimal capacity for functioning in sensorimotor areas, and requires nursing care, constant aid, and supervision.

In school age children (6 to 20 years), intellectual disability or learning disability is classified at one of the following levels:

  • The child can learn academic skills up to approximately sixth-grade level by the late teens, and can be guided toward social conformity.
  • The child is unlikely to progress beyond second-grade level in school. The child can benefit from training in social and occupational skills, and may learn to travel alone in familiar places.
  • The child can talk or learn to communicate, can be trained in basic health habits and other functional habits. The child is unable to benefit from vocational training.
  • The child has some motor development and may respond to minimal or limited self-help training.

In adults (21 years and above), an intellectual disability is classified at one of the following levels:

  • The individual can usually achieve social and vocational skills for minimal self-support but may need guidance and assistance when under unusual social or economic stress.
  • The individual may achieve self-maintenance in unskilled or semiskilled work under sheltered conditions but requires supervision and guidance when under mild social or economic stress.
  • The individual may contribute partially to self-maintenance under complete supervision and can develop self-protection skills to a minimal useful level in a controlled environment.
  • The individual may have some motor and speech development and may achieve very limited self-care but requires nursing care.
What causes intellectual disability?

Factors that cause intellectual disability can be genetic, developmental, environmental, or a combination. Genetic causes include chromosomal and inherited conditions. Developmental and environmental factors include prenatal exposure to infections and toxins. Environmental or acquired factors include prenatal trauma (e.g., prematurity) and sociocultural factors.  Among chromosomal disorders, Down syndrome and fragile X syndrome are the most common disorders that usually produce at least mild intellectual disability.

What is an Unspecified Intellectual Disability?

A diagnosis of “unspecified intellectual disability” is given to children over 5 years of age when it is either too difficult or impossible to assess the degree of intellectual disability through locally available procedures because of sensory or physical impairments, such as blindness or deafness, locomotor disability, severe behavior problems, or a co-occurring mental disorder. This diagnosis is only used in exceptional circumstances and requires reassessment after a period of time.

How can a child with intellectual disability be helped?

According to the American Association on Intellectual and Developmental Disabilities, a child or adolescent with an intellectual disability needs a degree of “environmental support” to develop a specific set of adaptive behaviors. This includes support for succeeding in the areas of communication, self-care, home living, social or interpersonal skills, use of community resources, self-direction, functional academic skills, work, leisure, health, and safety.

What are recommended intellectual disability treatments?

Treatments for children and adolescents with intellectual disability are based on assessment of each individual’s social, educational, psychiatric, and environmental needs.

Primary Prevention

Primary prevention is focused on eliminating or reducing the conditions that led to development of the intellectual disability, as well as associated disorders. Examples include:

  • Screening babies for phenylketonuria (PKU), and administering a low-phenylalanine diet when PKU is present, significantly alters the emergence of intellectual disability in those affected children.
  • Education on the importance of abstaining from alcohol during pregnancy
  • Optimal maternal and child healthcare
  • Family and genetic counseling for families with a history intellectual disability

Secondary and Tertiary Prevention

Prompt attention to medical and psychiatric complications of intellectual disability can diminish their course and minimize the disability. Hereditary metabolic and endocrine disorders, such as PKU and hypothyroidism, can be treated effectively at an early stage by dietary control or hormone replacement therapy.

Educational Interventions

Education for children with intellectual disability should include a comprehensive program that addresses academics and training in adaptive skills, social skills, and vocational skills. Particular attention should focus on communication and efforts to improve the child’s quality of life.

Behavioral and Cognitive-Behavioral Therapy

Behavior therapy has been used for many years to shape and enhance social behaviors and to control and minimize aggressive and destructive behaviors in individuals with intellectual disability. Positive reinforcement for desired behaviors and benign punishment (e.g., loss of privileges) for objectionable behaviors is helpful. Cognitive therapy, such as dispelling false beliefs and relaxation exercises, is also recommended for intellectually disabled persons who can follow instructions. Psychodynamic therapy has been used with patients and their families to decrease conflicts about expectations that result in persistent anxiety, rage, and depression. Psychiatric treatment methods require modifications that consider the patient’s level of intelligence.

Family Education

One of the most important areas of treatment in addressing intellectual disability in a child or adolescent is educating the patient’s family about ways to enhance competence and self-esteem while maintaining realistic expectations for the patient. Parents may benefit from continuous counseling or family therapy and should be allowed opportunities to express their feelings of built, despair, anguish, recurring denial, and anger about their child’s disorder and future.

Social Intervention

One of the most prevalent problems among individuals with intellectual disability is a sense of social isolation and social skill deficits. Therefore, a critical part of care should focus on improving the patient’s quantity and quality of social competence. Special Olympics International is the largest recreational sports program supporting this population, providing opportunities to not only improve physical fitness but to enhance social interactions, friendships, and self-esteem. A recent study confirmed the positive effects of Special Olympics on the social competence of the intellectually disabled adults who participated.


Aggression, Irritability, and Self-Injurious Behavior

Risperidone is helpful in treating disruptive behaviors in children with below-average intelligence, and has a good overall safety and tolerability profile. Studies have demonstrated small but significant improvement in cognitive ability with risperidone use.


Studies of methylphenidate (Ritalin) treatment in mildly intellectually disabled patients with ADHD have shown significant improvement in the ability to maintain attention and to stay focused on tasks. Risperidone also has been found to be beneficial in reducing symptoms of ADHD.

Clonidine has been used to ameliorate hyperactivity and impulsivity, and clinical ratings by parents and clinicians suggest its efficacy. Atomoxetine has been shown to be effective in children diagnosed with autism spectrum disorder and prominent ADHD features, and is used clinically in the intellectually disabled population.

Depressive Disorders

SSRI antidepressants have a relatively safe treatment record and are recommended when a depressive disorder is diagnosed in a child or adolescent with intellectual disability.

Stereotypical Motor Movements

Antipsychotic medications, including haloperidol (Haldol) and chlorpromazine, as well as atypical antipsychotics, are used in the treatment of repetitive self-stimulatory behaviors in children with intellectual disability when these behaviors are either harmful to the child or disruptive.

Obsessive-compulsive (OCD) Symptoms

Obsessive-compulsive symptoms often overlap with the repetitive stereotypical behaviors seen in children and adolescents with intellectual disability, particularly in those with autism spectrum disorder. SSRIs such as fluoxetine, fluvoxamine (Luvox), paroxetine, and sertraline have been shown to be effective in treating OCD symptoms in children and adolescents.

Explosive Rage Disorder

Antipsychotic medications, particularly risperidone, have been shown to be effective for the treatment of explosive rage. B-Adrenergic antagonists (beta-blockers) such as propranolol (Inderal) have been anecdotally reported to result in fewer explosive rages in some children with intellectual disability and autism spectrum disorder.

Do individuals with an intellectual disability tend to have other mental health problems?

Yes. Studies indicate that up to two-thirds of children and adults with an intellectual disability have another psychiatric disorder. The more severe the intellectual disability, the higher the risk for coexisting psychiatric disorders, including mood disorders, schizophrenia, ADHD, and conduct disorder. Children diagnosed with severe intellectual disability have a particularly high rate of autism spectrum disorder, and approximately 2 to 3 percent them meet the diagnostic criteria for schizophrenia.

Up to 50 percent of children and adults with intellectual disability meet the criteria for a mood disorder such as major depressive disorder, an anxiety disorder, or bipolar disorder.

A negative self-image and poor self-esteem are common features of mildly and moderately intellectually disabled persons who are aware of their social and academic differences from others. The perpetual sense of isolation and inadequacy has been linked to feelings of anxiety, anger, dysphoria, and depression.

What is Autism Spectrum Disorder?

Autism spectrum disorder is a developmental disability characterized by a wide range of impairments in social communication and behavior.A diagnosis of ASD now includes several conditions that used to be diagnosed separately: autistic disorder, Rett syndrome, Asperger syndrome, and pervasive developmental disorder not otherwise specified.

Autism spectrum disorder affects approximately 1 percent of the population.

What are the symptoms of Autism Spectrum Disorder in children?

Diagnostic criteria for autism spectrum disorder include deficits in social communication and restricted interests. Autism spectrum disorder is typically evident during the second year of life. In severe cases, a lack of social behavior may be noted even in the first year. Although language impairment is not a core diagnostic requirement, a child who has not developed any language by 12 to 18 months with diminished social behavior frequently will be diagnosed with autism spectrum disorder. In up to 25 percent of cases, some language develops and is subsequently lost.

Autism spectrum disorder in children with normal intellectual function and mild impairment in language function may not be identified until middle childhood when both academic and social demands are increased. Children with autism spectrum disorder often exhibit idiosyncratic intense interest in a narrow range of activities, resist change, and typically do not respond to their social environment in accordance with their peers.

Does the incidence of autism differ in boys and girls?

Yes. Autism spectrum disorder is diagnosed four times more often in boys than in girls.

Is Autism Spectrum Disorder genetic?

Studies suggest that autism spectrum disorder is partly genetic. Up to 15 percent of cases of the disorder appear to be associated with a known genetic mutation. However, in most cases, its expression is dependent on multiple genes. Researchers who screened the DNA of more than 150 pairs of siblings with autism spectrum disorder found evidence of two regions on chromosomes 2 and 7 containing genes that may contribute to autism spectrum disorder. Additional genes thought to be involved were found on chromosomes 16 and 17.

What are treatments for Autism Spectrum Disorder?

Comprehensive treatment for autism spectrum disorder includes intensive behavioral programs, parent training and participation, and academic/educational interventions to expand an individual’s social skills, communication and language. Medications used to treat autism spectrum disorder are mainly directed at improving behavioral symptoms rather than core features of the disorder. Symptoms targeted include irritability, aggression, temper tantrums and self-injurious behavior, hyperactivity, impulsivity, and inattention.

What are communication disorders that can occur in children?

The following disorders may be diagnosed under the DSM-5 category of “communication disorders.”

Language Disorder

Language abilities are substantially below those expected for the child’s age, resulting in limited communication, social participation, academic achievement, and/or occupational performance. The child has persistent difficulties in learning and using language due to shortcomings in comprehension or speaking, including:

  • Reduced vocabulary
  • Limited sentence structure
  • Impairments in discourse or ability to have a conversation

Language difficulties become evident during early childhood and are not due to hearing or other sensory impairment, motor dysfunction, or another medical or neurological condition.  In addition, the diagnosis of language disorder is given when the problem cannot be better explained by intellectual disability or global developmental delay.

Speech Sound Disorder

A diagnosis of “speech sound disorder” is given when a child has persistent difficulty with speaking that interferes with speech intelligibility or prevents verbal communication. The problem limits the child’s effectiveness in any of the following areas: social participation, academic achievement, or occupational performance. Symptoms begin in early childhood and the speech difficulties are not attributable to congenital or acquired conditions, such as cerebral palsy, cleft palate, deafness or hearing loss, traumatic brain injury, or other medical or neurological conditions.

Stuttering / Childhood-Onset Fluency Disorder

A diagnosis of stuttering, clinically referred to as “childhood-onset fluency disorder,” is given when a child has disturbances in the normal fluency and time patterning of speech that are inappropriate for the individual’s age and language skills. The problem begins in early childhood and persists over time and is characterized by one or more of the following:

  • Sounds and syllable repetitions
  • Sound prolongations of consonants as well as vowels.
  • Broken words (e.g., pauses within a word)
  • Audible or silent blocking (filled or unfilled pauses in speech)
  • Circumlocutions (word substitutions to avoid problematic words
  • Words spoken with an excess of physical tension
  • Monosyllable whole-word repetitions (e.g., “I-I-I-I see her.”)

The problem causes anxiety about speaking or limitations in any of the following areas: effective communication, social participation, academic or occupational performance. The diagnosis of stuttering is given when the difficulty speaking is not attributable to a speech-motor or sensory deficit, dysfluency associated with neurological injury (e.g., stroke, tumor, trauma) or another medical condition, and is not better explained by another mental disorder.

Social Communication Disorder

A diagnosis of “social communication disorder” is given when a child has persistent difficulties in verbal and nonverbal communication as shown by all of the following:

  • Lacks social communication behaviors, such as greeting and sharing information, in a manner that is appropriate for the social context.
  • Lacks ability to change communication to match the context or needs of the listener, such as speaking differently in a classroom than on a playground, talking differently to a child than to an adult, and avoiding use of overly formal language.
  • Has difficulty following rules for conversation and storytelling, such as taking turns in conversation, rephrasing when misunderstood, and knowing how to use verbal and nonverbal signals to regulate social interaction.
  • Has difficulty understanding what is not explicitly stated or ambiguous meanings of language (e.g., idioms, humor, metaphors, multiple meanings that depend on the context for interpretation).

For a diagnosis of social communication disorder, the symptoms cannot be attributable to another medical or neurological condition or to lacking abilities in word structure and grammar. Also, the behavior cannot be better explained by autism spectrum disorder, intellectual disability, global developmental delay, or another mental disorder.

Unspecified Communication Disorder

A diagnosis of “unspecified communication disorder” is given to patients with symptoms characteristic of a communication disorder that cause significant distress or impairment in social, occupations, or other important areas of functioning. However, the symptoms do not meet the full criteria for a communication disorder diagnosis or for any other neurodevelopmental disorder. 

What are treatments for stuttering?

Different types of therapeutic interventions have had some success in treating stuttering. 

  • Direct speech therapy provides systematic steps and rules of speech mechanics that the person can practice.
  • Relaxation techniques aim to reduce tension and anxiety during speech.
  • Individualized treatment combinations use direct speech therapy, relaxation techniques and directed speech modification.
  • Stutterers with poor self-image, anxiety disorders or depressive disorders may be helped additionally with cognitive behavioral therapy and pharmacotherapy, such as an SSRI antidepressant.
  • A self-therapy approach by the Stuttering Foundation of America informs stutterers that they can learn to control their difficulty partly by modifying their feelings and attitude about stuttering. The approach includes desensitizing the emotional reaction to, and fears of, stuttering and substituting positive action to control the moment of stuttering.
  • The Lidcombe Program has parents praise their child for periods of time when the child does not stutter and intervene when the child does stutter to ask the child to correct the stuttered word.
  • Parent-child interaction therapy under clinical study identifies stressor possibly associated with increased stuttering ad aims to diminish the stressors
  • Another therapy in clinical trials, which has shown some success with adults who stutter, teaches the patient to speak each syllable in time to a particular rhythm.
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Mental Health Library Sources:
Information included in all topics of the Mental Health Library comes from the Desk Reference to the Diagnostic Criteria From DSM-5 and Kaplan & Sadock’s Concise Textbook of Clinical Psychiatry. Complete diagnostic and treatment information may be found within these publications.
Information within the Mental Health Library is not intended to be used for self-diagnosis purposes. Rather, it is provided as a public educational service to make people aware of mental health conditions. Please consult a qualified mental health professional for a diagnosis of any suspected mental health illness.
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