Professional Guidelines for Diagnosing Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a complex disorder — for patients and for diagnosing clinicians. It’s critical for professionals to understand what constitutes a thorough ASD evaluation, and that a patient must demonstrate at least five of the seven criteria outlined in the DSM-5 in order to merit an autism diagnosis.

By Theresa Regan, Ph.D. Verified Medically reviewed by ADDitude’s ADHD Medical Review Panel Updated on May 22, 2024

Q: “Why is an autism diagnosis so complicated?”

A: The diagnostic criteria for autism spectrum disorder (ASD) were not published in the Diagnostic Statistical Manual ¹ until the 1980s, and even then the medical community’s understanding of autism was not complete — it was actually still hypothesized 40 years ago that ASD was related to poor parenting. As a culture, we’re still working to understand that the brain impacts behavior and interactions. We are much quicker to think that behavior is a reflection of discipline or a person’s character.

While “autism awareness” is growing — it’s tough to find an individual who doesn’t know the word and doesn’t understand that it’s an impactful public health condition — what we’re really lacking is holistic “autism recognition.” Few medical professionals and mental health care professionals can confidently say: “I know what autism looks like in the classroom, in the medical clinic, in families, and in neighborhoods.”

Since ASD presents with multiple behavioral characteristics, professionals often miss the big picture of autism and, instead, diagnose small pieces of the picture separately — for example, obsessive compulsive disorder (OCD), social anxiety, eating disorder, bipolar disorder, or attention deficit hyperactivity disorder (ADHD or ADD).

What are the criteria for an autism diagnosis?

Professionals should diagnose a patient with autism if the DSM-5 criteria are present. In addition to knowing the criteria, diagnosing clinicians should also be familiar with the supplemental information on ASD diagnosis included in the DSM-5.

All of these three criteria must be present to merit an autism diagnosis:

Social reciprocity: The patient struggles with back-and-forth social communication; she is unable to share thoughts and feelings and then to listen to the other person and be aware of what’s important to him or her.
Nonverbal social communication: The patient has difficulty making eye contact, respecting personal space, understanding gestures, and registering facial expression or tone of voice.
Developing, maintaining and understanding relationships are a significant challenge for the patient, especially relationships with peers. It is common for an individual on the autism spectrum to be more comfortable with people much older or much younger, but have trouble connecting with peers.

Two of these four criteria must be present to merit an autism diagnosis:

Repetition: The patient might display repetitive stereotyped movements, or tics, like hand flapping. He might communicate with repetitive verbalizations, such as echoing or quoting directly from movies or books. Repetitive use of objects is also common. Examples include lining things up, patterning objects, or handling objects in his hands.
Rigid behaviors and thinking: The patient will display concrete, black-or-white thinking, as if everything is either good or bad. She might struggle with abstract thinking or change.
Intense fixed interests or attachment to objects: The patient might be so obsessed with a particular topic or hobby that it is all that she talks about. The attachment to objects can have to do with collecting things related to the fixed interest or it could be indicative of hoarding behaviors.
Sensory processing: Over-reactivity to the sensory environment could be an issue. The patient might have trouble with lights being too bright or noises being too loud. Under-reactivity can be a problem as well. If the patient broke her collarbone, for example, she won’t realize it’s broken because she won’t feel much pain. She might also be fixated on sensory aspects of the environment, for instance, watching water flow or a fan turn.

What is included in a thorough autism evaluation?

Professionals who diagnose autism should be prepared to disclose to their patients the number of ASD assessments they have administered to adults and to children. Additionally, they should explain why certain criteria are met or not met.

Questionnaires and online quizzes should be used only as one part of an evaluation, never as a stand-alone method of evaluation. Potential questionnaires include the Social Responsiveness Scale ² or the Adult/Adolescent Sensory Profile ³ for sensory issues. Professionals should develop their own additional interview questions that personalize or build off of similar questionnaires.

The following suggestions can contribute to a thorough autism evaluation:

Ask the patient to explain how other people would describe him. See if he has a sense of how he impacts other people and how he’s viewed.
Ask how one person who knows the patient well might describe her differently than another person would. The patient’s inability to understand how different people experience her differently is often problematic.
Practice role-playing with the patient to see how he does with conversation.
Show the patient pictures of emotional faces and see if she can name the emotion being depicted.
Describe social scenarios to see if the patient understands what would be rude/polite or appropriate/inappropriate in certain settings.
Talk with family members or friends of the patient who can corroborate and give their perspectives.

The following information came from Theresa Regan, Ph.D and her webinar “Could I Be on the Autism Spectrum?” The Adults’ Guide to Pursuing an Accurate ASD Diagnosis. That webinar is available for replay here.