Newly homeless youth are likelier to engage in risky sexual behavior if they stay in nonfamily settings because they lack supervision and social support, a new study shows.

Researchers defined homeless youth as those who have been away from home for a period between one day and six months. Homeless settings include friends' homes, abandoned buildings or the streets.

The University of California Los Angeles (UCLA)-AIDS Institute study, carried in the online edition of the Journal of Adolescent Health, is the first time that researchers have followed newly homeless youth for any length of time to track how their behavior changes.

At the beginning of the two years, 77 percent said they were sexually active, but that percentage increased to 85 percent by the end of the period. Males were found to be more likely to have multiple sex partners if they lived in settings without family members and abused drugs.

For females, drug abuse was the primary predictor of risky sexual behavior. As for condom use, females were less likely to use them if they lived in a nonfamily situation or abused drugs; neither of these factors predicted condom use among males.