Many studies have confirmed the link between childhood sexual abuse and substance-related problems in adulthood. But a new investigation finds that being raped or molested at a young age also makes young girls far more likely to start drinking or doing drugs during their preteen years.

The study, published in the May issue of the journal Addiction, is the first to demonstrate that childhood sexual abuse has an early impact on girls’ use of alcohol, marijuana and tobacco, with many picking up their first drink before age 10.

Researchers conducted telephone interviews of 3,761 young women between the ages of 18 and 29, all of them twins. By examining twins, they were able to determine what effect sexual abuse had on risk for early substance use after accounting for influences, such as genetics and parenting practices, shared by family members.

When compared with girls who were not sexually abused, girls who were raped or sexually molested were four times as likely to use alcohol and more than twice as likely to begin smoking cigarettes before age 10. There was also a three and a half times greater probability they would begin using marijuana before age 14. Across the U.S. the average age at which girls first start drinking or smoking is 13 whereas that for trying marijuana is 17.

“This really shows that sexual abuse has such a profound impact,” says Judy Silberg, professor of clinical psychology at Virginia Commonwealth University who specializes in children’s behavioral and emotional disorders and was not affiliated with the study. “If they’re starting to use alcohol before age 10—wow.”

Beyond its effects on girls’ physical health, the study has particularly critical implications for their brain development, says Carolyn Sartor, assistant professor of psychiatry at Yale University School of Medicine and the leading author of the study. A recent report by the American Medical Association found that alcohol use during adolescence has a profoundly negative effect on memory and learning capabilities as well as reduces critical decision-making and reasoning skills.