Aims: This study examined the incidence of attention-deficit/hyperactivity disorder medication among children and adolescents by sex and age group in Finland during 2008-2019.

Methods: The data on children and adolescents aged 6-18 years receiving reimbursement for any attention-deficit/hyperactivity disorder medication was collected from the nationwide register on reimbursed purchases. The incidence was calculated as a ratio of the number of new users and the number of age and sex-matched population at risk. Negative binomial models were used to calculate rate ratios (RRs).

Results: In 2019, the incidence of attention-deficit/hyperactivity disorder medication was 13.4 per 1000 boys and 4.8 per 1000 girls. Among boys, the incidence became 3.7 times greater during the observed years (RR 95% confidence interval (CI) 2.0, 6.5, P<0.0001), whereas in girls it was 7.6 times greater (RR 95% CI 2.1, 27.4, P=0.0019). The boys had 2.8 times the incidence rate compared with the girls (RR 95% CI 2.2, 3.6, P<0.0001). The increase was associated with age only among boys (P=0.0001). The highest incidence rate 23.4 per 1000 individuals (95% CI 22.5, 24.4) was found in 2019 among 6-8-year-old boys.

Conclusions: The incidence of attention-deficit/hyperactivity disorder medication use among children and adolescents increased significantly in Finland during the study period. Incidence was higher among boys, but the increase was greater among girls. The most common group to start attention-deficit/hyperactivity disorder medication was 6-8-year-old boys. These findings warrant critical evaluation of the diagnostic and treatment policies currently available in Finland for the treatment of attention-deficit/hyperactivity disorder and related symptoms.