How Autism is Diagnosed

Autism spectrum disorder, commonly known as autism, is a developmental disorder that affects communication, social interaction, and behavior. Autism affects every individual differently, creating a vast spectrum ranging from mild to severe symptoms. Autism can usually be diagnosed in children as young as 2 years old, but the diagnosis might take several months or even years in some instances. Diagnosing autism is a complex process that involves a team of healthcare professionals. The diagnostic measures aim to identify the signs and symptoms of autism spectrum disorder based on the individual’s behaviors and developmental history. In this article, we’ll discuss how autism is diagnosed and the different diagnostic tools used by healthcare specialists.

Step 1: Screening Tests

Autism can sometimes be identified at 18 months or earlier. However, diagnosing autism in young children can be difficult because some traits might be associated with normal development. If parents or primary care physicians notice any inconsistencies in the child’s social, emotional, or communication development, they might recommend screening tests. The objective of screening tests is to identify developmental disorders early so that children can receive help and support. Screening tests are typically short questionnaires that ask parents or caregivers to answer questions about their child’s behavior or development. One of the most commonly used screening tests is the Modified Checklist for Autism in Toddlers (M-CHAT). The M-CHAT is a parent-report screening tool specifically designed for children aged 16 to 30 months. It consists of 23 questions that ask parents about their child’s cognitive, social, and behavioral skills. If children score above a certain threshold or parents have concerns, the healthcare specialist might recommend further testing.

Step 2: Comprehensive Diagnostic Evaluations

If screening tests indicate the likelihood of autism spectrum disorder, healthcare specialists may recommend a comprehensive diagnostic evaluation. This evaluation is more in-depth and typically conducted by neurologists, developmental pediatricians, or psychologists with training in diagnosing autism. The evaluation may be conducted over several sessions and involve different tests to observe the child’s behavior and interactions. Healthcare professionals evaluate the child’s communication, language, social interactions, repetitive behaviors, and sensory sensitivities. They also examine the child’s medical and developmental history and may conduct physical and neurological exams. The diagnostic process aims to rule out other developmental or medical conditions and diagnose conditions related to autism.

Step 3: Diagnostic Criteria

Autism spectrum disorder is diagnosed based on specific criteria listed in the Diagnostic and Statistical Manual of Mental Disorders-5 (DSM-5). The DSM-5 criteria provide healthcare specialists with the guidelines they need to diagnose autism spectrum disorder. The DSM-5 criteria take into account the severity of symptoms based on the level of support required by the individual. There are three levels of severity:

Level 1 – requiring support
Level 2 – requiring substantial support
Level 3 – requiring very substantial support

To diagnose autism spectrum disorder, the individual must meet two criteria:

1. Persistent impairment in reciprocal social communication and social interaction. This might include difficulties in initiating or responding to social interactions, abnormal nonverbal communication, or inability to establish relationships with peers.

2. Restricted, repetitive patterns of behavior, interests, or activities. This might include repetitive movements or behaviors, fixation on specific topics, or insistence on routines or rituals.

Step 4: Further Assessments

Since the autism spectrum extends from mild to severe symptoms, further assessments may be needed to provide a more accurate diagnosis. Additional assessments may include:

• Speech and Language Assessment
Assessment of the child’s speech and language skills can help identify communication difficulties that may be associated with autism. The assessment measures the child’s ability to understand language, express themselves, and use language in social settings.

• Cognitive Assessments
Cognitive tests measure intellectual abilities, such as attention, memory, and problem-solving skills. Cognitive assessments can identify learning difficulties that may be associated with autism spectrum disorder.

• Neuropsychological Assessments
A neuropsychological evaluation may be conducted by a specialist to evaluate the child’s brain function. The assessment helps identify any underlying neurological conditions that may be associated with autism.

In Conclusion

Diagnosing autism is a complex process that involves several healthcare professionals. Early screening and diagnosis are essential to ensure appropriate interventions and support are put in place. Understanding how autism is diagnosed can help families and caregivers recognize the signs and symptoms of autism and seek medical advice. If you have concerns about your child’s development, a consultation with a healthcare provider can provide guidance on appropriate screening and diagnostic tests to determine if autism spectrum disorder is present. Early intervention can offer significant benefits to children with autism and help them achieve their potential.



1. Who Can Diagnose Autism?

A diagnosis of autism should always be made by a qualified health professional. This can be a paediatrician, a child psychiatrist or a psychologist trained in diagnosing autism. Speech therapists and occupational therapists also work with children with autism while also assisting in the diagnosis process.

2. How Is Autism Diagnosed?

Autism is diagnosed using a range of assessments, tools and criteria including observations, parental reports and standardised tests. These tools look at a child’s communication skills, social interaction, play and behaviour. Generally, diagnosis will involve three steps; a developmental screening, a comprehensive diagnostic evaluation and a follow-up evaluation which may include further testing and observation.

3. What Age Is Autism Typically Diagnosed?

Autism can be diagnosed at any age, but early diagnosis and early intervention can make a significant difference in a child’s development. Many children receive a diagnosis between the ages of 2 and 4 but some children may not receive a diagnosis until later in life. It’s important to remember that every child with autism is different, and diagnosis should never be rushed.


1. American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). Arlington, VA: American Psychiatric Publishing.
2. Lord, C., Rutter, M., DiLavore, P. C., & Risi, S. (2001). Autism Diagnostic Observation Schedule. Los Angeles, CA: Western Psychological Services.
3. Mullen, E. M. (1995). Mullen Scales of Early Learning. AGS Editions.

American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). Arlington, VA: American Psychiatric Publishing.

Lord, C., Rutter, M., DiLavore, P. C., & Risi, S. (2001). Autism Diagnostic Observation Schedule. Los Angeles, CA: Western Psychological Services.

Mullen, E. M. (1995). Mullen Scales of Early Learning. AGS Editions.