That left one year of data from the post-Obamacare period.
The research team followed two groups: young people, ages 19 to 25, and a control group of adults, ages 26 to 34, before and after the coverage provision's implementation. This allowed researchers to filter out any changes affecting the entire health system and to isolate the effects of expanding coverage just to the younger group.
The study linked dependent coverage to a 7.2 percentage-point bump in insurance coverage among young adults, as well as self-reported increases in physical and mental health.
Dr. Robert Fortuna, assistant professor of medicine and pediatrics at the University of Rochester in Rochester, N.Y., said expanding access to health care likely contributed to the increases in health.
Often described as "young invincibles," young adults, in fact, "face many preventable health conditions, and relatively small changes in health care access may have a large impact on overall health," Fortuna explained.
While the study did not detect any statistically significant changes in the use of health services, such as doctor visits and hospitalizations, Chua said this wasn't surprising.
"I think you can make the argument that for a lot of these outcomes you wouldn't necessarily expect a change, because a lot of young adults are healthy at baseline," he said.
Also, the authors did not have access to 2012 data that could have revealed longer-term changes in young adults' use of health services.
In studies by The Commonwealth Fund, a New York City-based research and grant-making group, young adults who enroll in a parent's plan tend to have higher incomes than those who don't enroll.
"This is because young adults with lower incomes are less likely to have a parent with a health plan they can join," said Sara Collins, vice president for the Fund's health care coverage and access program.
Still, the Harvard study suggests that even those who weren't able to join a parent's plan "will realize similar benefits" by enrolling in private coverage through the new Obamacare marketplaces or through the law's Medicaid expansion, Collins said.