Direct answer
Ontario accepts previous autism diagnoses made under earlier DSM editions (DSM-IV, DSM-IV-TR) including Asperger syndrome and PDD-NOS for OAP eligibility without requiring re-assessment. The MCCSS explicitly states that prior diagnoses by qualified professionals remain valid. However, individuals diagnosed with Asperger syndrome or PDD-NOS may choose to seek updated assessment for personal or employment accommodation purposes. Re-assessment costs $2,500–$4,000 through private providers.
Start with the short answer, then reveal deeper context where helpful.
The DSM-5 (2013) merged four previously separate diagnoses — autistic disorder, Asperger syndrome, PDD-NOS, and childhood disintegrative disorder — into a single Autism Spectrum Disorder (ASD) diagnosis with severity levels 1-3. The two-domain criteria (social communication + restricted/repetitive behaviours) replaced the three-domain model. Sensory differences were added as a diagnostic feature.
The Ontario Autism Program accepts diagnoses made under any DSM edition by a qualified Ontario professional. You do not need a new assessment to access OAP services if you have an existing diagnosis of autism, Asperger syndrome, PDD-NOS, or childhood disintegrative disorder. The MCCSS policy explicitly recognizes prior diagnoses.
The DSM-5 (2013) merged four previously separate diagnoses — autistic disorder, Asperger syndrome, PDD-NOS, and childhood disintegrative disorder — into a single Autism Spectrum Disorder (ASD) diagnosis with severity levels 1-3. The two-domain criteria (social communication + restricted/repetitive behaviours) replaced the three-domain model. Sensory differences were added as a diagnostic feature.
Some individuals who met criteria for Asperger syndrome or PDD-NOS under DSM-IV may not meet DSM-5 ASD criteria. Research by Volkmar and McPartland (2014) estimated that 9-12% of individuals with prior PDD-NOS diagnoses might not meet DSM-5 criteria. However, clinical judgment and grandfathering provisions generally protect existing diagnoses.
The Ontario Autism Program accepts diagnoses made under any DSM edition by a qualified Ontario professional. You do not need a new assessment to access OAP services if you have an existing diagnosis of autism, Asperger syndrome, PDD-NOS, or childhood disintegrative disorder. The MCCSS policy explicitly recognizes prior diagnoses.
Reasons to consider voluntary re-assessment include: wanting a formal DSM-5 diagnosis for clarity, needing updated documentation for workplace accommodations, requiring a current psychological report for ODSP applications, or wanting a comprehensive assessment that identifies co-occurring conditions (ADHD, anxiety, learning disabilities) that were not assessed previously.
APA
American Psychiatric Association — DSM-5 Transition and Implementation Guide (2013)
MCCSS
Ontario Autism Program — Diagnostic Eligibility Requirements and Accepted Diagnoses (2024)
DSM-5 classifies autism into 3 support levels. Level 1 requires support, Level 2 substantial support, Level 3 very substantial support. Learn the differences.
In Ontario, autism can be diagnosed by psychologists, developmental pediatricians, psychiatrists, and some pediatricians. Learn the pathways and costs.
Adult autism diagnosis in Ontario costs $3,000-$5,000 privately with 2-12 week wait times. Learn about OHIP-covered options and how to get an assessment.
Commitment to Accuracy: Our data is verified against official government reports (FAO, MCCSS), peer-reviewed scientific literature, and accessible public records. Last updated: March 24, 2026.
Written by Spencer Carroll
Founder & Autism Advocate