It has been widely reported that ADHD is associated with increased medical costs and use of healthcare services. In Denmark, although treatment and care for children with ADHD is mainly provided by psychiatric hospitals, these children may also frequently use services at general medical hospitals because of coexisting medical conditions. This population-based historical study followed a Danish birth cohort* from birth until 12 years of age, comparing the mean number of visits to medical and psychiatric hospital-based services† in children with and without ADHD, in order to determine the independent effect of ADHD on use of hospital-based services and to identify risk factors associated with the use of medical and psychiatric services in children with ADHD.
A total of 532,553 children were included in the Danish birth cohort, with 11,360 (2.2%) of these children identified as having a clinical diagnosis of ADHD according to the International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10). More children were first diagnosed with ADHD at a psychiatric hospital (n=8965) compared with a medical hospital (n=2395); the mean age at first ADHD diagnosis was 8.5 years, with more males than females diagnosed with ADHD (3.8:1 ratio). Medical healthcare use‡ and psychiatric healthcare visits§ were higher for children with ADHD compared with those without ADHD. When ADHD was included as an explanatory variable for hospital-based service use, a multivariant Poisson regression analysis of the total cohort showed that ADHD was associated with both medical and psychiatric service use, with adjusted incidence rate ratio (IRR) estimates of ADHD of 1.38 (95% confidence interval [CI] 1.34–1.42) for medical hospital service use and 40.46 (95% CI 38.53–42.48) for psychiatric service use.
For use of psychiatric services, comorbid affective disorder/anxiety disorders/obsessive-compulsive disorder, autism spectrum disorder, intellectual disability, oppositional defiant disorder/conduct disorder and tic disorders were all associated with increased service use. Moreover, children with ADHD who had a parent with a psychiatric diagnosis showed higher adjusted IRR rates of medical and psychiatric service use (IRR 1.12 and 1.08, respectively) than those without. Similarly, the incidence of children with ADHD using psychiatric services with divorced or single parents was higher (IRR 1.08 and 1.14, respectively) than for children whose parents lived together. Finally, families with a higher income used medical services more (adjusted IRR 1.11), while a lower family income was associated with decreased use of psychiatric services (adjusted IRR 0.93).
In this study, ADHD and psychiatric diagnoses were based on ICD-10 criteria, and despite the large overlap between the ICD-10 and the diagnoses specified by the Diagnostic and Statistical Manual of Mental Disorders – 5th Edition (DSM-5TM), these results may not correspond to findings using the DSM-5TM, which may be a limitation of this study. Moreover, all possible comorbid psychiatric disorders were not accounted for in this analysis, which may be another study limitation.
The authors concluded that ADHD impacts the use of medical and psychiatric hospital-based services by children in Denmark in the first 12 years of life; however, the pattern of healthcare service use is complex and cannot be fully explained by only the child-, parental- or socioeconomic-related variables evaluated in this study.
*Danish national registries were used to identify all children born in Denmark between 1995 and 2002. This cohort was followed from birth until 12 years of age in national health registries to identify medical and psychiatric hospital service use in these children
†In Denmark, there are very few private hospitals and the healthcare system is free of charge, enabling socially equal access to qualified healthcare for all citizens. This supports the assumption that the data from national registries used in this study provide a good indication of healthcare service use
‡Healthcare use was defined as the number of outpatient visits and inpatient admissions to Danish medical hospitals or psychiatric services registered in the Danish National Patient Register and Danish Psychiatric Central Research Register, respectively, during the 12-year follow-up period
§Healthcare visits were counted as one record per day per outpatient clinic, with each inpatient admission counted for only one record
Laugesen B, Mohr-Jensen C, Boldsen SK, et al. Attention deficit hyperactivity disorder in childhood: healthcare use in a Danish birth cohort during the first 12 years of life. J Pediatr 2018; 197: 233-240.