The dependent-coverage mandate is one of the Affordable Care Act's most popular provisions.
It took effect in September 2010 and requires that health insurance companies allow people under age 26 to receive coverage through their parents' plans.
The rule applies regardless of whether the dependents are married, employed or living separately from their parents.
The report found that gaining coverage under the mandate did not affect the probability of employment, but it was associated with fewer work hours.
Researchers speculated that the policy might have broader social ramifications, perhaps making young people "less independent," according to lead study author and healthcare economist Kosali Simon.
The ability to gain coverage on a parent's plan "may change the way that [young adults] relate to their parents," Simon said in a statement.
"On the other hand," she added, "young people may become more independent as they find they can pursue other career development options than just seeking a job with good fringe benefits from the start."
In all, 13 percent of young adults eligible for coverage on their parents' plans remain uninsured.
The study will be published in the American Economic Journal: Economic Policy.