Background: Little is known about longitudinal changes in drug utilization in attention-deficit/hyperactivity disorder (ADHD).
Objective: To describe longitudinal trends in ADHD drug utilization and explore demographic differences among youths eligible for a large Southern state Medicaid program.
Methods: A cross-sectional and longitudinal analysis of 10 years of claims data for all Medicaid beneficiaries younger than 20 years of age with 6 months or more of continuous insurance (N = 2,131,953) was conducted. Annual prevalence, incidence, and persistence in ADHD medication use (stimulants and atomoxetine) were estimated based on pharmacy claims and clinician-reported ADHD diagnosis.
Results: ADHD prevalence increased 1.70-fold (95% CI 1.67 to 1.73) from 3.10% (21,904 of 705,573 beneficiaries) in fiscal year 1995-1996 to 5.27% (41,681 of 790,338) in 2003-2004, paralleled by a 1.84-fold (95% CI 1.81 to 1.87) increase in drug use to 4.63%. In 2003-2004, 0.89% of youths were diagnosed and newly started on drugs, reflecting a 1.38-fold (95% CI 1.33 to 1.43) increase over 1995-1996. One in five white males between the ages of 10 and 14 years (19.24%; 95% CI 18.81 to 19.67) received ADHD medication in 2003-2004. Males continued to be more likely diagnosed and treated than females (prevalence ratio [PR] in 2003-2004 = 2.96; 95% CI 2.90 to 3.03 vs 3.82; 95% CI 3.69 to 3.96 in 1995-1996), as were whites when compared with Hispanics (PR in 2003-2004 = 2.65; 95% CI 2.57 to 2.73 vs 3.78; 95% CI 3.57 to 3.99 in 1995-1996) and blacks (PR in 2003-2004 = 1.81; 95% CI 1.76 to 1.85 vs 2.00; 95% CI 1.93 to 2.07 in 1995-1996). The most common starting age throughout the study period was 5-9 years, with 2.45% (95% CI 2.37 to 2.52) new ADHD drug users in 2003-2004, but largest increases in prevalence were observed in adolescents 15-19 years of age, with 2.47% (95% CI 2.38 to 2.55) in 2003-2004 compared with 0.45% (95% CI 0.41 to 0.49) in 1995-1996. Medication persistence varied, with only 49.9% (95% CI 49.4 to 50.5) of new users receiving drugs after 1 year, with yet another 17.2% (95% CI 16.4 to 18.0) continuing for 5 years or more.
Conclusions: ADHD drug utilization continues to increase due to steady increases in diagnosis and chronic use of the drugs over several years. While racial, ethnic, and sex differences persist, the age distribution of drug users has shifted toward older children. These findings emphasize the need for studies that analyze determinants of treatment as well as outcomes, both benefits and risks, associated with long-term medication use.