This study reported on children/adolescents with ADHD referred to Finnish specialised health services, with respect to demographic characteristics, comorbidity profile and time trends in ADHD diagnosis. The study also investigated the validity of register-based ADHD diagnosis. The findings revealed an ascending trend in the diagnosis of ADHD in both males and females in the past 20 years and a high prevalence of psychiatric comorbidities associated with ADHD.
The study included 10,409 children/adolescents diagnosed with ADHD* according to the Finnish Hospital Discharge Register (date of birth: January 1991–December 2005). Mean age at first diagnosis was 7.6 years (0–19 years), and 84.0% and 16.0% were males and females, respectively. 80.6% of children were diagnosed with ADHD, 8.0% with hyperkinetic conduct disorder and 11.4% with other hyperkinetic disorders.
The children included in the study were grouped into five birth cohorts according to their year of birth: 1991–1993, 1994–1996, 1997–1999, 2000–2002 and 2003–2005. Results showed an increasing trend of ADHD diagnosis in children in the later-born birth cohorts compared with those born in 1991–1993, and a similar trend was seen among males and females.
A total of 76.7% of patients had ≥1 psychiatric comorbidity. The most common comorbid diagnoses were learning and coordination disorders (48.1%), conduct disorders (28.1%), anxiety disorders (13.6%), autism spectrum disorders (12.0%) and depression (8.9%). The most common comorbidities in males were conduct disorders and autism spectrum disorders, whereas learning and coordination disorders, anxiety disorders and depression were significantly more common among females.
In order to assess the validity of register-based diagnosis, the parents of 69 children (mean age 12.1 years) diagnosed with ADHD within the past year were interviewed† and asked to rate 18 ADHD symptoms and evaluate school feedback on impulsivity, inattention and hyperactivity symptoms. The responses of parents were assessed to derive a diagnosis for ADHD based on Diagnostic and Statistical Manual of Mental Disorders – 4th Edition (DSM-IV) criteria. Out of the 69 children included in the validation study, 61 (88%) had a positive ADHD diagnosis according to DSM-IV criteria. The symptoms criteria of DSM-IV were also met by 95% of children and the symptoms were considered impairing by 95% of parents. These results demonstrate a good validity of ADHD diagnosis based on parent interviews with the Development and Well-Being Assessment scales.†
The generalisability of the results of this study to all children with ADHD is limited, as subjects have been sampled from specialised services, which introduces a bias towards more severe cases of ADHD. Also, interviews were not conducted with children who did not have ADHD (control group).
The finding that ADHD is detected more frequently in males warrants more careful assessment of girls for ADHD symptoms in healthcare services.
*Based on International Classification of Diseases, 10th Edition criteria
†Using the Development and Well-Being Assessment (DAWBA). The DAWBA consists of interviews for parents and children and questionnaires for teachers
Joelsson P, Chudal R, Gyllenberg D, et al. Demographic characteristics and psychiatric comorbidity of children and adolescents diagnosed with ADHD in specialized healthcare. Child Psychiatry Hum Dev 2016; 47: 574-582.