Comorbidities and comedication among individuals in treatment for ADHD: a Danish nationwide study

To examine the prevalence of comorbidities and the use of psychiatric comedication among individuals in medical treatment for attention deficit hyperactivity disorder (ADHD), in comparison to a matched control group from the general population.

This nationwide case-control study included 1,082,378 Danish individuals aged 7-64 of whom 98,398 had at least one prescription of ADHD medication during 2023. Data was collected over an observation period spanning from 2013 to 2023. Cases were matched to controls (1:10) from the general population on birth year and sex. Data were obtained and accessed through The Danish Health Data Authority. Associations were estimated using conditional logistic regression models.

Somatic and particularly psychiatric comorbidities were more common among individuals in ADHD treatment across all age groups. Among those in ADHD treatment 46.7% had at least one comorbidity compared to 23.3% in the control group. The use of psychiatric comedications (besides ADHD medication) was likewise more common among individuals in ADHD treatment (32.7%) compared to the controls (7.2%). The association estimates from conditional logistic regression revealed a higher likelihood of somatic and psychiatric comorbidities among those in ADHD treatment in all age groups. Females in ADHD treatment had 4.48-4.50 times higher odds of comorbidities compared to females not in ADHD treatment (OR_{7 - 17 years} = 4.48, 95% CI: 4.27-4.70; OR_{18 - 29 years} = 4.50, 95% CI: 4.37-4.64). Similar patterns were observed for males but with slightly lower ORs (OR_{7 - 17 years} = 2.35, 95% CI: 2.27-2.44; OR_{18 - 29 years} = 3.38, 95% CI: 3.28-3.50).

This study reveals that both prevalence of somatic and psychiatric comorbidities and the use of psychiatric comedication are significantly higher among individuals in ADHD treatment. The highest occurrence is seemingly among females aged 7-17 year and 18-29 years. The coexistence of ADHD with other somatic and psychiatric conditions can constitute a more complex disease burden, necessitating enhanced disease management strategies to reduce complications and enhance quality of life. Longitudinal studies are needed to confirm the temporal association of these results.