Asperger syndrome in males over two decades: stability and predictors of diagnosis.

Objective: To examine the diagnostic stability of a childhood diagnosis of Asperger Syndrome (AS) into adulthood in a prospective longitudinal study, and identify the predictors of stability.

Methods: One hundred males with AS diagnosed in childhood (T0) according to Gillberg's AS criteria, were followed up prospectively into adulthood over an average of 19 years (range 13-26 years). Fifty males (mean age 30 years) participated in this second follow-up (T2) of the cohort. Seventy-six had participated in a previous follow-up (T1) at mean age 22 years (47 participated in both follow-ups). Diagnosis at T2 was assessed using three sets of diagnostic criteria (Gillberg's AS criteria, DSM-IV Pervasive Developmental Disorder (PDD) and DSM-5 Autism Spectrum Disorder (ASD) criteria) and compared to previous assessments. Background predictors of diagnostic stability were analyzed. General functioning at T2 was assessed and compared to T1.

Results: There was a decline in the stability of AS diagnosis over time, the rate dropping from 82% at T1 to 44% at T2, when using the Gillberg criteria. There was also a significant decrease in the rate of cases fulfilling any PDD diagnosis according to the DSM-IV, from 91% at T1 to 76% at T2 in the 47 cases followed up twice. Severity of autism spectrum symptoms at T1 was the main predictor of diagnostic stability at T2. Twenty percent of those meeting criteria for a PDD diagnosis according to DSM-IV, did not meet DSM-5 ASD criteria although they had marked difficulties in everyday life.

Conclusion: Asperger Syndrome, when considered as an ASD/PDD diagnosis, was fairly stable into adulthood, but there was a significant increase over time in cases no longer meeting criteria for an ASD diagnosis according to the DSM-IV, or AS according to the Gillberg criteria. Cases with a stable diagnosis showed significantly more core ASD symptoms in adolescence/young adulthood.