The largest minority on the sexual-orientation spectrum – the mostly heterosexuals, estimated at around 7 percent of the general adult population – report more health problems than heterosexuals and somewhat fewer than bisexuals.

So say the Cornell psychologists who put mostly heterosexuals – also known as MHs or mostly straights – on the map (and on the minds of human-sexuality scholars and therapists): Ritch Savin-Williams, professor of human development and director of the Cornell Sex and Gender Lab in Cornell’s College of Human Ecology, and Zhana Vrangalova, Ph.D. ’14.

Their study was published in the April 2014 Journal of Sex Research as “Psychological and Physical Health of Mostly Heterosexuals: A Systematic Review.”

“Compared to heterosexuals, mostly straight youth and adults reported more physical and mental health problems,” said Vrangalova, now an adjunct instructor in the Psychology Department at New York University.

“MHs are more likely to experience depression, anxiety, body dissatisfaction and eating disorders (from anorexia to obesity) and are more likely to attempt suicide or self-harm than heterosexuals,” the Vrangalova said. “They also report more health-risk behaviors, like substance use and sexual risk taking, and have more sexual/reproductive health and physical health issues.”

Finally, the mostly straights expressed more experiences of victimization, lower connectedness in their personal and social relationships, and were more likely to inhabit stressful or risky environments than heterosexuals, the psychologists learned. On the positive side, MHs were more educated and suffered fewer broken bones, compared with others on the continuum.

Compared to bisexuals, mostly heterosexuals fared somewhat better on most examined outcomes, although these conclusions were more tentative as there were fewer bisexual comparison groups, and the differences were often small or in the opposite direction.

This first-of-its-kind review of MH health status drew on 60 other studies that were based on 22 datasets across the United States, Canada, Australia, New Zealand and Norway between 1991 and 2013.

The authors described MHs as “more same-sex oriented than exclusive heterosexuals, but less so than substantial bisexuals, in their sexual/romantic attraction, fantasy, physiological arousal, and recent and lifetime sexual behavior.”

The term, MH, gained greater currency in the last five years or so, according to Vrangalova, who co-authored a much-cited 2013 paper, “Mostly Heterosexual as a Distinct Sexual Orientation Group,” in the journal Developmental Review, with Savin-Williams.

They argued for a fourth group in the conventional, three-way (heterosexual/bisexual/lesbian-and-gay) framework. They suggested a spectrum or continuum where sexual-orientation self-identity “is not always either/or.”

While MHs were found to be the largest sexual-minority group – comprising about 4 percent of men and 9 percent of women in the general population – that proportion nearly doubles among college students, Vrangalova commented. “The college years are a time when young people are freer to experiment in all things, to look around and to think about their identities.”

So far MHs go largely unnoticed, the authors noted, writing: “They are likely to socialize in the sexual-majority culture because there is no visible MH subculture nor are MHs actively encouraged to join LGB spaces.”

All the more reason, Vrangalova and Savin-Williams believe, that health professionals should learn “to identify MHs in their practice so they can adequately assess risk and direct care and counseling.”

Public-health professionals and youth-based organizations, they say, “need to be aware of MHs’ substantial presence in the general ‘heterosexual’ population and work to make their services and messages as inclusive as possible.”

The study was funded in part by American Institute of Bisexuality.