Gay teenagers are more likely to try to kill themselves if they live in a Republican area that is less tolerant of homosexuality.
A report in the Daily Mail said Columbia University psychologist Mark Hatzenbuehler came up with a "social index," focusing his study in towns in Oregon.
The index measures such factors as the number of same-sex couples, registered Democratic voters, schools with gay-straight alliances and those with anti-discrimination policies.
Gay teenagers living in counties with the lowest social index scores were 20% more likely to have attempted suicide than those in counties with the highest.
Hatzenbuehler said suicide attempts were even higher among straight teenagers in the less tolerant areas.
He said the results show "environments that are good for gay youth are also healthy for heterosexual youth."
"Is it surprising? No. Is it important? Yes," said Dr Robert Blum of Johns Hopkins Bloomberg School of Public Health in Baltimore. "It takes our relatively superficial knowledge and provides a bit more depth. Clearly, we need lots more understanding, but this is very much a step in the right direction."
The study was published in the journal Pediatrics.