Age at ADHD diagnosis and educational outcomes: a register-study of Finnish 1990-1999 birth cohorts

Abstract Background Early diagnosis of ADHD is often recommended, but it is unknown how age at diagnosis predicts educational outcomes. We investigated how age at diagnosis is associated with school performance, educational enrollment, completed degrees, and school dropout. Methods We used national registry data on 579,459 individuals born in Finland between 1990-1999 and identified ADHD from records of healthcare visits and medication purchases. We used linear regression models to examine how age at diagnosis (6-20) was associated with grade point average (GPA) (4-10, fail-excellent) at the end of compulsory basic education (age around 16) and logistic models to predict probabilities of completed upper secondary degrees (vocational or general), enrollment in upper secondary (vocational or general) or tertiary education, and school dropout at age 20 by age at diagnosis. Results Compared to non-diagnosed peers, ADHD diagnosis at any age was associated with poorer school performance, choosing vocational instead of general upper secondary education, less tertiary studies and more school dropout. If a diagnosis was received during compulsory basic education, younger age at diagnosis predicted higher GPA (7.2 to 6.6), higher probability to complete a general upper secondary degree (20.8% to 6.8%) by age 20, and lower probability of school dropout (14.6% to 29.2%) at age 20. However, after age 16, older age at diagnosis predicted higher GPA, more degrees in general upper secondary education, and more enrollment in tertiary education. Conclusions Late ADHD diagnosis during compulsory basic education may lead to lower school performance, constrain educational track choices, and increase the probability of school dropout. The results support the recommendations of a diagnosis during the first school years, while those who receive a diagnosis towards the end of compulsory education have a particularly high rate of school dropout and could benefit from targeted support. Key messages • An earlier ADHD diagnosis predicted better school performance, more academic track choices, and less school dropout than a diagnosis towards the end of compulsory basic education. • The results support recommendations of an early diagnosis. Those who are diagnosed in adolescence may need targeted support to continue in their studies after compulsory education.