Shared Symptoms of Autism and Mental Retardation

toddler boy

Learning the shared symptoms of autism and mental retardation can help you seek a correct diagnosis. Autism and mental retardation are two separate neurological conditions with some similar symptoms and important differences. Parents sometimes have trouble getting a correct diagnosis when a child has severe autism or mental retardation because of shared characteristics that deal with developmental delays, communication problems, learning difficulties and self-care.


Autism is a pervasive developmental disorder (PDD) that affects brain development primarily in communication, language development and social skills. It is one of five PDDs , which includes Asperger's syndrome, fragile X syndrome, Rett syndrome and childhood disintegrative disorder and pervasive developmental disorder-not-otherwise-specified (PDD-NOS).

Mental Retardation or Intellectual Disability

Mental retardation, also known as intellectual disability, is a type of developmental disability that produces significant limitations in intellectual functioning ability and adaptive behaviors. These limitations result in problems with reasoning, learning or problem-solving as well as communication and social skills difficulties.

Shared Symptoms of Autism and Mental Retardation

Since autism and intellectual disability share similarities, diagnosis is sometimes difficult in early childhood. The shared symptoms of autism and mental retardation can include the following:

  • Early childhood developmental delays
  • Limited speech and vocabulary
  • Problems understanding verbal instruction and following directions
  • Learning difficulties
  • Attention problems
  • Difficulty communicating with peers
  • No pretend play
  • Needs life skills training and assistance with self-care and safety
  • Echolalia or repeating words and phrases out of context
  • Repetitive behavior or stimming activities for self-stimulation, such as hand flapping or rocking back and forth
  • Sensory processing issues, which can result in an unusual reaction to a taste, smell, sight or sound
  • Symptoms vary and range from mild to severe

Differences Between Autism and Mental Retardation

Despite the similarities between autism and mental retardation, there are a number of important differences between autism and intellectual disability, such as the following:

  • Autism cases vary in IQ range, with both below and above average test results. In fact, it is quite common for people with severe autism to have an IQ of 70 or below. Some people with autism have high IQs, and a small population are considered genius level. This differs from people with intellectual disability who generally have IQs of 70.
  • A person with intellectual disability develops and performs slower than his peers but he gains skills at an even pace. A person with autism's progress may not be so clear cut. The autistic person may make progress in some areas easily but has difficulties with skills, such as language, communication and social interaction.
  • Intellectual disability may present speech and vocabulary challenges but not to the same degree as a case of severe autism, which can render someone nonverbal.
  • A person with autism may experience mindblindness or appear to lack empathy for others because of problems understanding the emotions and emotional responses of others. Mindblindness is not as common in mental retardation.

Comorbidity of Autism and Intellectual Disability

Another reason that correct diagnosis is sometimes difficult is the comorbidity of autism and mental retardation, when a person has both autism and intellectual disability. When this occurs, a doctor might miss one of the conditions during diagnosis. Diagnosis of all medical conditions can help parents get the right treatment for an affected child. Parents seeking a diagnosis should research all symptoms, the possible related conditions and get at least two medical opinions to confirm a diagnosis.

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Shared Symptoms of Autism and Mental Retardation