Pathways to autism diagnosis in adulthood.

Area of Science:

• Neurodevelopmental Disorders
• Psychiatry
• Health Services Research

Background:

• Autism Spectrum Disorder (ASD) diagnosis in adulthood is increasingly recognized.
• Understanding the diagnostic journey, or Trajectories of Diagnoses (TDs), preceding an adult autism diagnosis is essential.
• Previous research has not fully elucidated the diverse pathways leading to adult autism diagnosis.

Purpose of the Study:

• To explore and characterize the different sequences of psychiatric and neurodevelopmental diagnoses that occur before a first autism diagnosis in adults.
• To identify distinct patterns of prior diagnoses that may inform diagnostic processes and clinical care for adults with autism.

Main Methods:

• Retrospective cohort study utilizing health administrative data from Quebec, Canada (2002-2017).
• Included 2799 adults with a first autism diagnosis between 2012-2017.
• State sequence analysis applied to identify patterns in diagnoses including Autism, Intellectual or Developmental Disabilities (IDDs), Schizophrenia Spectrum Disorder (SSD), Bipolar Disorder (BD), Depressive Disorder (DD), Anxiety Disorder (AD), and Attention-Deficit/Hyperactivity Disorder (ADHD).

Main Results:

• Five distinct Trajectories of Diagnoses (TDs) were identified.
• Younger adults showed varied TDs (Types 1-3) with mixed diagnoses, SSD/AD, or IDDs/DD/AD/ADHD.
• Middle-aged/older adults exhibited distinct TDs (Types 4-5) predominantly linked to SSD or BD, with high healthcare utilization.

Conclusions:

• Adults follow multiple, distinct pathways to an autism diagnosis.
• Recognizing these diverse diagnostic trajectories is vital for improving differential diagnosis.
• Addressing co-occurring psychiatric and neurodevelopmental conditions within these pathways is critical for effective clinical management.