When it comes to attention deficit/hyperactivity disorder, the focus is usually on children. But a new study found that ADHD treatments are actually growing at a much faster rate among adults than among kids.

According to the analysis released Thursday by Medco Health Solutions, the number of adults ages 20 to 44 using ADHD medications more than doubled from 2000 to 2004, outpacing increases in the kids 19 and under by nearly 44 percent.

And spending on ADHD drugs for the adult age group grew by more than 325 percent during the same time period.

"This analysis clearly shows that ADHD is no longer just about children. Adults are increasingly seeking diagnosis and treatment for themselves -- not just for their kids," said Dr. Robert Epstein, chief medical officer of Medco, in a news release. "Although it's surprising to see this shift, it is in line with research that shows that half the children on medication for ADHD will still need drug therapy as adults."

The analysis, which included prescription data of 2.4 million patients nationwide, also showed a significant jump in the number of adult women taking medications to treat ADHD. Among women ages 20 to 44, use of ADHD medications has more than doubled over the four-year analysis period, a growth rate 21 percent greater than their male counterparts.