How Is Autism Diagnosed? A Complete Guide to the Evaluation Process

Understanding Autism Diagnosis

Diagnosis can be overwhelming. Knowing what to expect helps. The CDC says diagnosis is reliable by age 2. But many are diagnosed later.

Early diagnosis is crucial. It opens the door to early intervention services. Research shows these services improve long-term outcomes. Sooner access to support is better.

Early Signs That May Prompt Evaluation

Parents often spot differences first. Some signs are clear, others are subtle. Autism Speaks lists these early signs:

• Limited or no eye contact
• Not responding to name by 12 months
• Limited pointing or waving by 12 months
• No single words by 16 months or two-word phrases by 24 months
• Loss of previously acquired language or social skills
• Limited interest in other children
• Unusual play patterns (lining up toys, repetitive actions)
• Strong reactions to sensory input (sounds, textures, lights)
• Repetitive movements or behaviors

For a more comprehensive overview, see our guide on autism symptoms and signs.

The Diagnosis Process: Step by Step

Step 1: Developmental Screening

The AAP recommends screening at 18 and 24 months. This is done at checkups. It involves:

• Brief questionnaires completed by parents about their child's development
• Observation of the child during the visit
• Discussion of any concerns

Common screening tools include the M-CHAT-R/F (for toddlers) and the CAST (for older children). A positive screen doesn't mean a child has autism—it indicates the need for further evaluation.

Step 2: Comprehensive Diagnostic Evaluation

If screening shows signs, you need a full evaluation. The NIMH says this includes:

Who Can Diagnose Autism?

Several professionals can diagnose autism:

• Developmental Pediatricians: Pediatricians trained in child development and behavior
• Child Psychologists: Specialists in child behavior and testing
• Child Psychiatrists: Doctors specializing in children's mental health
• Pediatric Neurologists: Specialists in the brain and nervous system
• Multidisciplinary Teams: Groups of specialists working together

The American Psychological Association notes that multidisciplinary team evaluations are often considered the gold standard, as they bring multiple perspectives to the assessment.

Diagnostic Criteria: DSM-5

Diagnosis uses criteria from the DSM-5. To be diagnosed, a person must show:

1. Persistent deficits in social communication and interaction across multiple contexts:
   • Deficits in social-emotional reciprocity
   • Deficits in nonverbal communication
   • Deficits in developing, maintaining, and understanding relationships
2. Restricted, repetitive patterns of behavior, interests, or activities (at least 2 of 4):
   • Stereotyped or repetitive movements, use of objects, or speech
   • Insistence on sameness, inflexible adherence to routines
   • Highly restricted, fixated interests that are abnormal in intensity or focus
   • Hyper- or hypo-reactivity to sensory input or unusual interest in sensory aspects of environment

Symptoms must be present in early childhood and cause clinically significant impairment. The DSM-5 also specifies support level requirements (Levels 1-3).

Common Screening and Assessment Tools

Finding Evaluation Services in New Hampshire

For families in New Hampshire seeking autism evaluation, here are options available in Manchester, Nashua, and throughout the state:

• Children's Hospital at Dartmouth-Hitchcock: Offers comprehensive developmental evaluations
• NH Early Supports & Services (Birth-3): Free evaluations for children under 3
• School District Evaluations: Free through your local school district (ages 3+)
• Private Developmental Pediatricians and Psychologists: Often shorter wait times
• University-Based Clinics: UNH and other institutions may offer services

See our comprehensive guide to New Hampshire autism resources for more information on local services.

What to Expect: Timeline and Costs

Timeline

• Wait times: 3-12+ months for many providers (varies significantly by area)
• Evaluation itself: 2-4+ hours, often spread across multiple appointments
• Results: Typically provided 1-4 weeks after evaluation completion

Costs

• With insurance: Often covered as diagnostic testing; check your specific plan
• Without insurance: $1,500-$5,000+ for comprehensive evaluation
• Free options: Early Intervention (0-3), school districts (3+)

Many insurance plans cover autism diagnostic evaluations. See our guide on insurance coverage for autism services for more information.

After Diagnosis: Next Steps

A diagnosis helps you get support. Here are the next steps:

1. Take time to process: It's normal to experience a range of emotions
2. Learn about autism: Understanding helps you advocate and support your child
3. Connect with support: Parent support groups, autism organizations, other families
4. Access early intervention: ABA therapy and other evidence-based services
5. Explore school services: IEPs, special education, accommodations
6. Address co-occurring conditions: Many autistic individuals have additional diagnoses
7. Build your team: Therapists, educators, medical providers who understand autism

Download our free Early Intervention Checklist: First 100 Days After Diagnosis for a week-by-week action plan.

Frequently Asked Questions

Related Resources

• Autism Screening Guide for Parents
• What Causes Autism? Fact vs. Fiction
• Understanding Late Autism Diagnosis
• Free M-CHAT-R Screening Tool
• Benefits of Early Intervention
• Free Parent Guides and Resources