Jan. 23 (HealthDay News) -- Same-sex couples are as committed and happy in their romantic relationships as heterosexual couples, find two studies in the January issue of the journal Developmental Psychology.

The authors of the studies say their findings challenge the stereotype that same-sex relationships aren't as healthy or secure as heterosexual pairings.

In the first study, researchers at the University of Urbana-Champaign compared 30 committed gay male and 30 committed lesbian couples to 50 engaged and 40 older married heterosexual couples, as well as dating heterosexual couples.

The researchers found that all the couples had positive views of their relationships, but the more committed couples (gay or straight) resolved conflict better than the heterosexual dating couples.

The belief that committed same-sex relationships are "atypical, psychologically immature, or malevolent contexts of development was not supported by our findings," noted lead author Glenn I. Roisman. "Compared with married individuals, committed gay males and lesbians were not less satisfied with their relationships."

Roisman added that gay males and lesbians "were generally not different from their committed heterosexual counterparts on how well they interacted with one another, although some evidence emerged the lesbian couples were especially effective at resolving conflict."

The second study -- conducted by researchers from the University of Washington, San Diego State University and the University of Vermont -- examined how sexual orientation and legal status affected relationship quality among 65 gay male and 138 lesbian couples in civil unions, 23 gay male and 61 lesbian couples not in civil unions, and 55 married heterosexual couples.

The three-year study found that same-sex couples were similar to heterosexual couples in most relationship areas and that legal status didn't seem to be the overriding factor affecting same-sex relationships.

Regardless of civil union status, same-sex couples were more satisfied with their relationships, reported more positive feelings toward their partners, and reported less conflict than married heterosexual couples.

The researchers did find that same-sex couples not in civil unions were more likely to end their relationships than same-sex couples in civil unions or married heterosexual couples. This suggests that protections offered by a legalized relationship may have an impact on same-sex couples, said the researchers, who plan to examine that question in future research.

SOURCE: American Psychological Association, news release, Jan. 22, 2008