The dramatic rise in the number of children given a diagnosis of attention-deficit hyperactivity disorder (ADHD) and a prescription for stimulant pharmacotherapy for its treatment has been well established (1). Follow-up studies have documented the persistence of ADHD into adulthood, with estimates that one- to two-thirds of individuals who were given a diagnosis in childhood continue to manifest symptoms into adulthood.

We used data from the National Ambulatory Medical Care Survey (NAMCS) to evaluate whether there has been an increase among adults in the number of office visits in which a diagnosis of ADHD was recorded. The NAMCS is an ongoing annual survey of a representative sample of U.S. office-based physician practices. We extracted all records with a recorded diagnosis of ADHD for patients aged 20 years or older for the years 1995 through 2002. We combined the data into two-year intervals to enhance sample size and derived annualized mean visits (1). Unweighted sample sizes for visits in which a diagnosis of ADHD was recorded were 99 in 1995-1996, 64 in 1997-1998, 106 in 1999-2000, and 142 in 2001-2002.

As shown in F1, over this time frame weighted national estimates of the number of these annualized office-based physician visits increased 2.5-fold (p<.05), from 583,000 in 1995-1996 (95 percent confidence interval [CI]=329,000 to 837,000), to 1,462,000 in 2001-2002 (CI=994,000 to 1,930,000).

After adjustment for population growth, the rate per year of office-based visits per 1,000 U.S. population aged 20 years or older that resulted in a diagnosis of ADHD more than doubled, increasing from 3.1 per 1,000 in 1995-1996 to 7.1 in 2001-2002. A majority of office visits included a prescription for stimulant pharmacotherapy, increasing from 61.7 percent in 1995-1996 to 76.2 percent in 2001-2002 (F1). Over the eight years examined, 70.2 percent of the office visits were reported by psychiatric specialists, 52.8 percent were by male patients, and 97.1 percent were by Caucasian patients (including Hispanics). The mean age was 38.4 years (range, 20 to 89). A diagnosis of another mental disorder was recorded for 56.7 percent of these visits. Depression was the dominant comorbid disorder.

As with the findings for children, the rate of adults who are seeking medical care for ADHD has increased significantly. The NAMCS data collection form was not changed over this time frame and cannot account for the increasing trend. Unfortunately, reasons for the increase cannot be discerned with NAMCS data. The increase may be, in part, a result of heightened awareness by physicians and media attention. By 2001-2002, office visits by adults accounted for 21.8 percent of all office visits that resulted in a diagnosis of ADHD, compared with 17.4 percent in 1995 to 1996.

The authors thank David A. Woodwell, B.A., for statistical assistance.

The authors are affiliated with the department of health policy and administration at Washington State University, P.O. Box 646510, Pullman, Washington 99164-6510 (e-mail, lrobison@wsu.edu). Harold Alan Pincus, M.D., and Terri L. Tanielian, M.A., are editors of this column.