Seasonality and the changing adult/child prescription ratios in ADHD therapy.

Approximately seven million people were prescribed a treatment for attention deficit hyperactivity disorder (ADHD) between November, 2006, and October, 2007: 3.8 million ages 0 to 17 years and 3.2 million age 18 years and older. To investigate prescribing trends, we obtained monthly total prescriptions from January, 2003, through October, 2007, for two age groups: patients under 18 years and patients age 18 years and older. The 0 to 17 years age group has demonstrated significant seasonality with total monthly prescription volume dropping between 22 and 29 percent between May and July, depending on the year. In contrast, prescribing trends for adults age 18 years and older have been steadily growing over the time period and do not exhibit any seasonal variation. Interestingly, in July, 2007, for the first time, ADHD total prescriptions for adults were larger than total prescriptions for children.