New Study Points To Genetic Link In Male Homosexuality

A large study of gay brothers adds to evidence that genes influence men's chances of being homosexual, but the results aren't strong enough to prove it.

Some scientists believe several genes might affect sexual orientation. Researchers who led the new study of nearly 800 gay brothers say their results bolster previous evidence pointing to genes on the X chromosome.

Dr. Robert Green, a medical geneticist at Harvard Medical School, called the new study "intriguing but not in any way conclusive."

The work was published Monday by the journal Psychological Medicine. The National Institutes of Health paid for the research.

The researchers say they found potential links to male homosexuality in a portion of chromosome X and on chromosome 8, based on an analysis of genetic material in blood or saliva samples from participants.

Chromosome X is one of two human sex chromosomes; the other is chromosome Y, present only in men.

The study authors note that animal research suggests a gene located in one region of chromosome X may contribute to some sexual behavior; it's one of the same regions cited in the new study.

Specific causes of homosexuality are unknown. Some scientists think social, cultural, family and biological factors are involved, while some religious groups consider it an immoral choice.

Study participant Dr. Chad Zawitz, a Chicago physician, called the research "a giant step forward" toward answering scientific questions about homosexuality and helping reduce the stigma gays often face.

Being gay "is sort of like having certain eye color or skin color — it's just who you are," Zawitz said. "Most heterosexuals I know didn't choose to be heterosexual. It's puzzling to me why people don't understand."