Sexuality, sexual orientation, sexual behavior — These terms are often used interchangeably, but in reality, it's not so easy to categorize. Sometimes a person’s behavior and sexual identity misalign, according to a new new study on sexually active teens. This finding is the latest to suggest sexuality has become more fluid and can't be easily predicted.

Published in the Journal of Adolescent Health, the research found about one in five lesbian and four in five bisexual teen girls who are sexually active have had a recent male sex partner. The study included almost 3,000 girls, and looked at their behavior in discussing barriers, like condoms and dental dams, with their most recent sex partner. Thirty-two percent of lesbians reported having this discussion compared to 62 percent of bisexual girls and 73 percent of straight girls.

"Our findings highlight that sexual orientation labels and sexual behavior don’t always align — especially during the teen years," said lead author Michele Ybarra, president of the non-profit research incubator Center for Innovative Public Health Research, in a press release. "This means that lesbian and bisexual girls may be having unprotected sex with boys — and girls."

The findings also showed lesbians were significantly younger on average when they first had sex, at about 13.8 years, compared to bisexual (15.1) and heterosexual (15.5) girls. Bisexual girls were more likely to have had sex than their heterosexual peers, and both bisexual and lesbian girls had more lifetime partners. The data was collected from the 2010-2011 Teen Health and Technology Study, which surveyed 2,823 girls, aged 13-18 in the U.S.

The research could have important implications for schools and clinics, according to study co-author and University of British Columbia nursing professor Elizabeth Saewyc.

"Sexual health education should be comprehensive and cover sexual health for everyone," she said. "Programs need to teach all youth about safe sexual practices for the kinds of sex they’re having, and that means teaching pregnancy prevention and condom negotiation skills to lesbian and bisexual girls too."

Co-author Margaret Rosario, a professor of psychology at City University of New York pointed out the importance of understanding adolescence as a time of self-discovery, including sexual identity and sexual attractions.

"Experimentation is normal, which is why adolescent health professionals need to make sure that every young person has the skills she needs to keep herself safe," she said.

Several studies have examined the overall health of lesbian and bisexual women compared to their straight counterparts, and reported poorer health in general. These minority women are often overlooked in the health care system, and researchers suggest exposing clinicians to all types of patients so they can accurately and effectively educate and treat lesbian and bisexual patients.

Source: Ybarra M, Rosario M, Saewyc E, Goodenow C. Sexual Behaviors and Partner characteristics by Sexual Identity Among Adolescent Girls. Journal of Adolescent Health. 2016.