Childhood Diagnoses in Individuals Diagnosed With Autism in Adulthood

Abstract Autism is a developmental condition, where symptoms are expected to occur in childhood, but a significant number of individuals are diagnosed with autism for the first time in adulthood. Here we use the National Danish Patient Registry to investigate diagnoses given in childhood among those that are diagnosed with autism in adulthood (N = 2199). We found that most childhood diagnoses were given after the age of 12, and attention-deficit hyperactivity disorder, affective disorders, anxiety, and stress disorders were the most prevalent childhood diagnoses. However, 69% of males and 61% of females with adult autism diagnoses had not received any of the included diagnoses before the age of 18. In most cases, the late autism diagnosis is therefore unlikely to be explained by either misdiagnosis or diagnostic overshadowing. This result is at odds with the prevailing notion that autistic symptoms tend to diminish with age. Therefore, further research is warranted to examine how early signs of autism may have manifested among these individuals, and how similar they are to autistic people diagnosed earlier in their development. Milder to moderate cases of psychiatric conditions that have been solely treated by family physician or school psychologists may not be fully included in our dataset.