In the nine months after the Affordable Care Act raised from 19 to 25 the age through which dependents could be covered by their parents’ plan, about 2.5 million more young adults gained health insurance than would have been able to without the law, the U.S. Department of Health and Human Services announced Wednesday. Of that age group, a population that is traditionally less likely than others to be insured, 64 percent were covered before President Obama’s health care overhaul legislation took effect in September 2010, and 73 percent were covered in June 2011. It is unclear how many of the newly insured are college students. HHS announced in January that 1 million 19- to 26-year-olds had gained insurance thanks to the legislation, meaning that the pace of new coverage slowed somewhat. The rise in coverage is clearly attributable to the Affordable Care Act, HHS said, because the percentage of adults age 26-35 with health insurance stayed stable at 72 percent.