Washington: Researchers from Washington State University have established a categorical distinction between people who are heterosexual and those who are not.
The study also identified several alarming mental health issues like depression among non-heterosexuals.
By analysing the reported sexual behaviour, identity and attraction of more than 33,000 American adults, they found that three percent of men and 2.7 percent of women are not heterosexual.
They also found notable issues on several mental health fronts.
The findings are a clear departure from the homosexual-heterosexual continuum used to describe sexual orientation since it was hypothesised by US-based sexologist Alfred Kinsey in 1948.
However, the findings do support more recent biological hypotheses of sexual orientation.
"There are distinct qualitative differences in sexual orientation which means that there are distinct categories of people based on sexual orientation," said Alyssa Norris, doctoral candidate and lead author of the study.
Nearly three out of 10 non-heterosexual men met the diagnostic criteria for depression.
Non-heterosexual women were much more likely to abuse or depend on alcohol.
Non-heterosexual men and women were more likely to meet the criteria for anxiety and other mood disorders and to think about suicide.
According to the researchers, the social stigmatisation of gays, lesbians and other non-heterosexuals could be a factor in their mental health.
"By actually getting some understanding of how to categorise people and the unique challenges they face, we're getting a lot more insight into their well being and their experiences," Norris wrote.
Another implication of the findings is that these leave little room for calling homosexuality a lifestyle choice.
"People who use the language of 'choice' and 'lifestyle' are negating 'born that way' or any of the terminology that would assume that these are genuine differences that are legitimate," the authors noted in a paper published in the journal Psychological Science.