Adolescent girls reported high rates of sadness, suicidal thoughts and sexual violence, as did teenagers who identified as gay or bisexual.Nearly three in five teenage girls felt persistent sadness in 2021, double the rate of boys, and one in three girls seriously considered attempting suicide, according to data released on Monday by the Centers for Disease Control and Prevention.The findings, based on surveys given to teenagers across the country, also showed high levels of violence, depression and suicidal thoughts among lesbian, gay and bisexual youth. More than one in five of these students reported attempting suicide in the year before the survey, the agency found.The rates of sadness are the highest reported in a decade, reflecting a long-brewing national tragedy only made worse by the isolation and stress of the pandemic.“I think there’s really no question what this data is telling us,” said Dr. Kathleen Ethier, head of the C.D.C.’s adolescent and school health program. “Young people are telling us that they are in crisis.”The Youth Risk Behavior Survey was given to 17,000 adolescents at high schools across the United States in the fall of 2021. The survey is conducted every two years, and the rates of mental health problems have gone up with every report since 2011, Dr. Ethier said.“There was a mental health crisis before the pandemic — it just didn’t catch everyone’s attention the way it does now,” said Dr. Cori Green, the director of behavioral health education and integration in pediatrics at Weill Cornell Medicine in New York City.Still, Dr. Green said that she is seeing more of her young patients test positive on screenings for depression. “The pandemic led to more social isolation — a risk factor for depression,” she said.Tips for Parents to Help Their Struggling TeensCard 1 of 6Are you concerned for your teen?