Gays and straights of the opposite sex share some characteristics in the area of the brain responsible for emotion, mood and anxiety, a new study has found, suggesting sexuality may be a biologically fixed trait.
of brain scans conducted at the
Karolinska Institute in Stockholm, Sweden, has revealed that there are similarities in the symmetry among lesbians and straight men, and gay men and straight women in areas of the brain that were 'fixed' at birth.
"That was the whole point of the study, to show parameters that differ, but which couldn't be altered by learning or cognitive processes," says Ivanka Savic, who conducted
the study.
Brain scans of 90 volunteers showed that the brains of straight men and lesbians were slightly asymmetric with the right hemisphere slightly larger than the left while the brains of gay men and straight women were not.
The researchers also measured blood flow to the amygdala - part of the brain that governs fear and aggression - and found similarities in the connectivity patterns in gay men and straight women as well as gay women and straight men.
In straight women and gay men, the connections were mainly into regions of the brain that manifest fear as intense anxiety while in straight men and gay women, the connections were in regions of the brain that trigger the "fight or flight" response.
"This is significant," Savic says, "and fits with data showing that women are three times as likely as men to suffer from mood disorders or depression. Gay men have higher rates of depression too", she says, "but it's difficult to know whether this is down to biology, homophobia or simply feelings of being 'different'."
Savic added that the study can't say whether the differences in the brain are inherited or due to exposure to sex hormones (such as testosterone) in the womb or if they are responsible for sexual orientation.
This is something, however, that they plan to look at in a further study of newborn babies to see if it can help predict future sexual orientation.
"These observations motivate more extensive investigations of larger study groups and prompt for a better understanding of the neurobiology of homosexuality," Savic says.
Gay or straight, it may be in the brain
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