Trends in adult attention deficit hyperactivity disorder and psychiatric comorbidities over time

Background

The number of adult patients diagnosed with attention deficit hyperactivity disorder has increased in recent years. However, longitudinal changes in psychiatric comorbidities among these patients have not been fully characterized. Previous studies have reported that psychiatric comorbidities are highly prevalent in adult attention deficit hyperactivity disorder, but changes in the distribution and proportion of these comorbidities over time remain unclear. In particular, it is important to examine whether specific comorbid conditions have become more or less prominent over time. This study aimed to examine temporal trends in adult attention deficit hyperactivity disorder and associated psychiatric comorbidities using nationwide data. These findings may provide important information for understanding changes in clinical characteristics of adult attention deficit hyperactivity disorder patients over time.

Methods

We conducted a retrospective analysis using National Health Insurance data from 2009 to 2024. Adults aged 18 years and older diagnosed with attention deficit hyperactivity disorder (ICD-10 F90.x) and prescribed methylphenidate were included in the analysis. Interrupted time series analysis was performed to evaluate monthly trends in the number of patients, with September 2016 defined as the reference point for changes in trend. Monthly trends in both the absolute number and proportion of major psychiatric comorbidities were analyzed based on ICD-10 diagnostic codes. Selected comorbidities included bipolar disorder (F31), depressive disorders (F32), anxiety disorders (F41), sleep disorders (F51), and neurodevelopmental disorders.

Results

The number of adult attention deficit hyperactivity disorder patients receiving methylphenidate increased over time across the study period. Interrupted time series analysis showed no significant trend prior to September 2016 (p=0.887) and no significant level change at the intervention point (p=0.212). However, a statistically significant increasing trend was observed after September 2016 (β=44.59, p<0.001), indicating a continuous increase in patient numbers over time. The increase in patient numbers was more pronounced in younger age groups and in female patients compared to older age groups and males. The number of patients with psychiatric comorbidities also increased over time. This increasing pattern was consistently observed across multiple psychiatric comorbid conditions during the study period. While depressive disorders (F32) and anxiety disorders (F41) consistently accounted for a large proportion of comorbidities throughout the study period, the proportion of bipolar disorder (F31) and sleep disorders (F51) showed increasing trends over time. In contrast, some neurodevelopmental comorbidities were relatively more prominent in earlier periods and showed stable or relatively decreasing patterns in later periods. In additional analyses stratified by the presence of depressive disorders within one year prior to methylphenidate prescription, patients with depressive disorders showed higher rates of other psychiatric comorbidities, including bipolar disorder, anxiety disorders, and sleep disorders, compared to those without depressive disorders.

Conclusions

Adult attention deficit hyperactivity disorder patients increased over time, with a significant upward trend after September 2016. Psychiatric comorbidity patterns varied across conditions, with increasing proportions observed in bipolar disorder and sleep disorders over time.

References

No references