New research from the Centers for Disease Control and Prevention on adolescents’ mental health during the coronavirus pandemic suggests that for many teenagers who were ordered to stay at home, home was not always a safe place.

A nationwide survey of 7,705 high school students conducted in the first half of 2021 built on earlier findings of high levels of emotional distress, with 44.2 percent describing persistent feelings of sadness or hopelessness that prevented them from participating in normal activities, and 9 percent reporting an attempt at suicide.

It also found high rates of reported abuse, with 55.1 percent of teenage respondents saying they suffered emotional abuse from a parent or another adult in their house in the preceding year, and 11.3 percent saying they suffered physical abuse.

In the survey, emotional abuse was defined as swearing, insulting or belittling; physical abuse was defined as hitting, beating, kicking or physically hurting.

Research conducted before the pandemic, in 2013, showed that self-reports of parental abuse were substantially lower, with 13.9 percent of respondents ages 14 to 17 reporting emotional abuse during the preceding year, and 5.5 percent reporting physical abuse.

Abuse was only one of the stressors that teenagers reported at home, according to the new study. Twenty-nine percent of those interviewed in the survey reported that a parent or another adult in the home lost a job, and 24 percent said that they had experienced hunger.

The data underscores the protective role that schools can play in the lives of young people, especially those grappling with racism or gender identity, said Kathleen Ethier, who heads the adolescent and school health program at the C.D.C.

“Schools provide a way of identifying and addressing youth who may be experiencing abuse in the home,” she said, calling the reported rise in physical abuse “beyond worrisome” and the rise in suicidal behavior “hugely significant.”

“These data really confirm that we are in a severe crisis in terms of mental health among young people, particularly among female students and students who identify as lesbian, gay or bisexual,” she said.

Researchers and clinicians have expressed alarm about a sharp decline in the mental health of young people during the pandemic, which was described as “devastating” in a rare public advisory from the U.S. surgeon general in December.

After much of the country went into lockdown, emergency room visits for suicide attempts rose 51 percent for adolescent girls in early 2021 as compared with the same period in 2019, according to the surgeon general’s report. The figure rose 4 percent for boys. A C.D.C. report released in February found that emergency room visits by teenage girls relating to eating disorders had doubled during the pandemic.

Research released this week from the Adolescent Behaviors and Experiences Survey from the C.D.C. adds to those findings.

More than one in three high schoolers experienced poor mental health, with 44.2 percent reporting persistent feelings of sadness or hopelessness. Nearly 20 percent said they considered suicide, and 9 percent said they had attempted suicide during the previous year.

“That is hugely significant,” Dr. Ethier said. “That means a significant portion of our young people are telling us they don’t want to live right now.”

The rise in suicidal behavior during lockdown is especially pronounced among young women and students who identify as lesbian, gay or bisexual. Researchers worry “about those youth being separated from school and being home with families who may not be supportive of their sexual identify or sex orientation or gender identity,” Dr. Ethier said.

Dr. Moira Szilagyi, the president of the American Academy of Pediatrics and a specialist in abuse cases, said adolescents benefit from access to the large network of adults who are present at school.

“It exposes you to a whole other group of adults and peers,” she said. “There is a sea of people there, and among them — your teacher, your coach, the school administration — there are caring adults youth can seek out, and who identify when a youth isn’t doing well.”

The C.D.C. data showed that mental health was better among students who described a strong sense of “connectedness” or closeness with people at school, even when they were attending school remotely.

Previous research has shown that children who were unable to complete assignments during the pandemic lockdown also reported higher levels of anxiety and depression.

A longitudinal study of 168 children ages 5 to 11 who are patients at Boston Medical Center found a sharp rise in symptoms of depression and anxiety during the pandemic, to 18 percent from 5 percent. Worse mental health was correlated with caregiver depression and increased screen time, as well as failure to complete assignments.

The findings underline that school “is good for kids on multiple levels,” said Dr. Andrea E. Spencer, a child psychiatrist at Boston Medical Center and one of the paper’s authors.

“Families are extremely important, but often that peer group is not replaceable within the confines of the family home,” Dr. Spencer said. “Then you add parent stress on top of that, and it adds up to increased conflict in a house where no one can escape from each other. That recipe is not going anywhere good.”

Under normal circumstances, clinicians would “mobilize support to those families and really wrap around them and provide people in the home with resources,” Dr. Spencer said. But during periods of intense spread, public health conditions required much more isolating at home, which is “exactly the opposite of what we try to do for kids who are at risk,” she said.