The US Centers for Disease Control and Prevention (CDC) said Friday that emergency department visits for suspected suicide attempts by teenage girls rose significantly last year compared to 2019, highlighting the mental health impact of the pandemic.

"By early May 2020, ED visit counts for suspected suicide attempts began increasing among adolescents aged 12-17 years, especially among girls," the health agency said in a report.

Between July 26 to August 22, 2020, the average number of visits in girls of this age was 26 percent higher than the same period in 2019.

During February 21 to March 20, 2021, it had shot up an alarming 51 percent compared to the same period in 2020. For boys of the same age, the rise in emergency room visits was four percent.

Past research prior to the pandemic has also found self-reported suicide attempts are consistently higher among adolescent females than among males.

But "the findings from this study suggest more severe distress among young females than has been identified in previous reports during the pandemic, reinforcing the need for increased attention to, and prevention for, this population," the authors wrote.

The study was not designed to tease out the risk factors leading to increased suicide attempts.

But it said: "Young persons might represent a group at high risk because they might have been particularly affected by mitigation measures, such as physical distancing (including a lack of connectedness to schools, teachers, and peers)."

It also noted barriers to mental health treatment, increases in substance use, and anxiety about family health and economic problems, as possible risk factors.

According to the data tracking site Burbio, two percent of US school students are attending classes completely virtually, 70 percent have gone back to in-person learning, and 28 percent are learning via a hybrid of both.

The findings were not disaggregated by factors such as sex, race, income, sexual orientation and gender identity due to limitations in national data.

The Trevor Project, a US suicide prevention organization for LGBTQ youth, said in January LGBTQ youth face many of the same challenges as their peers but have reported additional stress at being confined with unsupportive parents and losing access to identity-affirming spaces.