The Senate’s effort to replace the Affordable Care Act — which greatly increased the number of young people covered by health insurance — could drive many of them back off again. And many of those who remain will be paying more for less coverage, or will be priced out of the market altogether.

The good news: The Senate Republicans’ version of an earlier House bill does keep a popular provision of the ACA allowing young adults up to age 26 to stay on their parents’ insurance and some young adults will enjoy lower premiums in the private insurance marketplaces.

The bad news, according to a report from Kaiser Health News, is the bill would also “dramatically reduce health coverage and care for other young adults, according to the bill’s many critics, which include the American Medical Association and the American Hospital Association.”

If states opt out of requiring insurers to provide benefits such as maternity care, mental health care, and prescription drugs — features which get regular use by young adults — millennials won’t be getting the care they need. In addition, while they might find the premiums more attractive and thus buy coverage they might otherwise not have, when they come to use their policies, they could find gaps in coverage just where they need it.

One of those areas could be mental health care. An NBC report points out mental health problems are on the rise among college students. Citing data from the National Alliance on Mental Illness, more than 75 percent of all mental health conditions begin before the age of 24 — making millennials, particularly those in college, most at risk.

The report also cites the Center for Collegiate Mental Health at Penn State University which says, based on data it gathers from 139 institutions, the number of students seeking help soared 50 percent between 2015 and 2016. Mental health care is not high on the priority list in the Senate bill.

Young adults, says KHN, could also be subject to other cost increases: larger deductibles, less help with out-of-pocket expenses, and for some, no subsidies to help pay for premiums, because the bill would reduce the income threshold for eligibility.

KHN reports approximately 27 percent of the 12.2 million consumers who signed up for health insurance through exchanges in 2017 were 18 to 34 years old. Covered California, the state’s exchange, put the number of its enrollees in that age group at 37 percent for this year.

It also cites Walter Zelman, chairman of the public health department at Cal State-Los Angeles, who says those who will face the most damage in the Senate bill are millennials covered by Medicaid. Not only does the Senate bill stop the expansion of Medicaid which was responsible for so many people signing up, but it cuts available funding for the program.