Actor Zac Efron and actress Michelle Pfeiffer speak at The Trevor Project's "Trevor Live" fundraising dinner in 2011. The Trevor Project provides crisis intervention and suicide prevention services to lesbian, gay, bisexual and transgender young people. Reuters

In her suicide note found Sunday, 17-year-old Leelah Alcorn begged people to "fix society." As a transgender girl rejected by her parents and peers, Leelah lamented the world she left. "My death needs to mean something," she wrote, and it has -- her story spread across the Internet, reminding people that as a year of historic progress toward LGBT rights came to an end, there is still a long way to go. Awareness campaigns and updated school policies have increased support for youths in the past five years, but teen suicide remains a major problem in the U.S.

"Even though the overall cultural climate seems to have shifted for the better, I still think there are a variety of reasons why some teens feel that they're not loved or valued or respected because of this or they're going to encounter problems coming out," Dr. Todd Savage, president-elect of the National Association of School Psychologists, said.

Leelah, from Kings Mill, Ohio, died after being hit by a tractor-trailer on the highway Sunday morning. Hours later, a scheduled posting appeared on her blog. It was her suicide note. The post told the story of how she, then named Joshua, came out to her parents as transgender at 14. They forced her into conversion therapy and took her out of school, leaving Leelah depressed and friendless. She couldn't wait to turn 18 to start transitioning, she wrote, so she killed herself.

Overall, lesbian, gay, bisexual and transgender youths are four times more likely to attempt suicide than heterosexual youths, and teen suicide rates in general are on the rise nationally. Centers for Disease Control and Prevention data show 2,088 people between the ages of 10 and 19 killed themselves in 2012. That's about 300 more than in 2002.

The United States saw a concerted effort to stop teen suicide a few years ago when several boys committed suicide after being bullied in school. In 2010, 13-year-old Seth Walsh hanged himself in California because his sixth-grade peers wouldn't stop taunting him. Also that year, Indiana 15-year-old Billy Lucas killed himself for similar reasons, and Rutgers University freshman Tyler Clementi died of suicide in 2011 after his roommate secretly broadcast Clementi kissing another male. The deaths prompted outreach campaigns like the It Gets Better Project, which features thousands of videos from LGBT people telling stories of how their lives improved as they grew up.

But popular projects and Americans' growing awareness of LGBT rights sometimes can't combat what goes on inside scared teens' heads. For example, some youths may internalize the political backlash to marriage equality in media reports. "It's those things that send messages to LGBT youth that it's still not OK to be this way," Savage said, adding, Things get better; sometimes they get worse in the process of being improved."

It's also difficult to develop strategies for addressing the issue. With other conditions, such as post-traumatic stress disorder or cancer, researchers can pinpoint which treatments work and which don't. Suicide is hard to analyze because the only people who go through it are deceased. This means the best practices for treating suicide are just common practices -- or "what we think are the most effective," according to David W. Bond, vice president of programs for the Trevor Project.

One of the best ways to remedy the situation is to focus on education, Bond said. Teens can often drown out themes of societal rejection if they have personal support from an adult. Savage said parents, teachers, administrators, nurses and counselors who support students should be visible and available. They should create safe spaces and organizations like Gay-Straight Alliance clubs. Schools should update their policies to be inclusive, which several institutions have done this month.

The U.S. Department of Education released a memo Dec. 1 confirming transgender students' protection under Title IX anti-discrimination laws. Minnesota approved a new rule allowing high school transgender athletes to play on the team for the gender with they most identify. Barnard College in New York announced it was reviewing its admission policies because "the time has come for us to examine how we, as a women’s college, define 'women,'" according to a Dec. 11 letter from its president.

Changes such as these need to take place not only at schools but everywhere teens are -- "circles and circles of widening environments that the person finds themself in," Bond said. More awareness means more mental health services, which means better treatment for LGBT teens feeling suicidal.

"This is very large public health issue, and it's going to require the investment of a lot of resources and time and energy from multiple players to start making a large impact," he said.