3.1M young adults gained health coverage since law took effect

Two years after health reform passed, 3.1 million young Americans now have access to health insurance, the government said.

NEW YORK (CNNMoney) -- More than 3.1 million young Americans now have health insurance, thanks in part to a provision in the health care reform law that allows parents to add dependents up to age 26 to their insurance plans.

That number is up from last June, when 2.5 million young adults ages 19 through 25 who would otherwise have been uninsured gained health care coverage, according to the Department of Health and Human Services.

One of the key provisions of the Affordable Care Act was that insurers allow dependents who don't have access to other employer-based health care coverage to remain on their parents' plans until their 26th birthday.

Prior to this mandate, dependents who were on their parents' plans lost coverage when they became too old to qualify as a dependent, or when they graduated from school or changed jobs, according to HHS.

Since the provision went into effect in September 2010, the proportion of adults ages 19 through 25 with insurance increased to 75%, or nearly 3.1 million, last December, up from 64%.

"This policy doesn't just give young adults and their families peace of mind, it also gives them freedom," HHS Secretary Kathleen Sebelius, said in a statement.

"As they begin their careers, they will be free to make choices based on what they want to do, not on where they can get health insurance," she said.

Young adults -- ages 30 and younger -- are consumers least likely to have health insurance. Prior to the Affordable Care Act, many in this age group couldn't afford coverage. And many who could, and who were healthy, chose not to in order to save money. They became known as "young invincibles."

Health reform hangs in the balance. The health care reform law also requires all Americans to buy health insurance by 2014 or pay a fine. The intended goal is to force more uninsured Americans, including young adults who have opted out in the past, to buy insurance.

But that provision, known as the individual mandate, has sparked controversy. The Supreme Court is currently reviewing the constitutionality of the individual mandate and is expected to announce its ruling on the law later this month.

The court could decide to uphold the law, strike it down completely, or partially.

If the entire law is axed, both health insurance companies and employers who offer health coverage will no longer be mandated to cover young adult dependents under their parent's policies.

Earlier this month, a number of big health insurers, including two of the largest -- UnitedHealthcare (UHC) and Humana (HUM, Fortune 500) -- committed to offering some provisions of health reform, including coverage of adult dependents up to age 26, regardless of how the court rules.

However, industry experts said consumers shouldn't count on their employer offering this benefits if the law is struck down.

"This provision is the most questionable," said Tracy Watts, senior health care consultant with benefits consulting firm Mercer. "Employers didn't offer this benefit before the law was passed and it has increased costs for them."