Tufts OpenCourseware
Authors: John Morgan, Bonnie F. Zimble

Autism Spectrum Disorders:

Causes and Diagnosis

Special Care in Dentistry
John Morgan, DDS
Tufts University School of Dental Medicine, 2008

Study Questions

  1. What three avenues of research are beginning to shed light on the causes of Autism Spectrum Disorders?

  2. What are the two stages of diagnosis?

  3. Under what conditions is a comprehensive diagnostic evaluation indicated?

     According to the National Institute of Mental Health 

“Research into the causes, the diagnosis, and the treatment of autism spectrum disorders has advanced in tandem. With new well-researched standardized diagnostic tools, ASD can be diagnosed at an early age. And with early diagnosis, the treatments found to be beneficial in recent years can be used to help the child with ASD develop to his or her greatest potential.”

What Causes Autism Spectrum Disorders? 

While it is not currently known what causes ASDs, research into the biological bases of autism is progressing rapidly. Advances in brain imaging technology holds promise for understanding how the structure and function of the brain differs in autism. At least six areas of the brain have been implicated based on postmortem and magnetic resonance imaging (MRI) studies.1 The role of neurotransmitters is also under investigation. Finally, twin and family studies have indicated an “underlying genetic vulnerability to ASD.”2 In fact, a large study is underway that involves collecting genetic (DNA) samples from families with more than one member with autism. It is hoped that “the most important genes will be found,” which will “enable scientists to learn what the culprit genes do and how they can go wrong.”3 

When and how are ASDs diagnosed?

Diagnosis usually progresses through two stages. First, developmental screening for ASD should be part of a pediatrician’s "well child" check-up. NIMH advises parents that “If your child's pediatrician does not routinely check your child with such a test, ask that it be done.”  Behavioral indicators such as pretend play, pointing and other early communicative and social skills are observed and can point to the possibility of ASD in children younger than 2 years of age. If this is the case, a second-stage follow-up may necessitate that a comprehensive diagnostic evaluation be conducted. This is accomplished by a “multidisciplinary team that includes a psychologist, a neurologist, a psychiatrist, a speech therapist, or other professionals who diagnose children with ASD.”3 


  1. Akshoomoff N, Pierce K, Courchesne E. The neurobiological basis of autism from a developmental perspective. Development and Psychopathology, 2002; 14: 613-634.

  1. Korvatska E, Van de Water J, Anders TF, Gershwin ME. Genetic and immunologic considerations in autism. Neurobiology of Disease, 2002; 9: 107-125.

  1. National Institute of Mental Health, Autism Spectrum Disorders (Pervasive Developmental Disorders), 2005, http://www.nimh.nih.gov/publicat/autism.cfm.