For a long time, researchers have thought that all the outside changes that happen in your early teens—school, peers, and family‑are what decide whether a kid starts abusing substances. But now some, including a group in Melbourne, Australia, and Seattle, think it may be more basic than that—just plain old puberty messing with your brain.

What the researchers wanted to know: Does the time kids start experimenting with drugs and alcohol correspond to age, grade level, or puberty?

What they did: The researchers did the study in Washington State and Victoria, a state in southern Australia. Students in grades 5, 7, and 9—about 5,800 kids in all—filled out surveys with questions on tobacco, alcohol, and marijuana use and about pubertal development. They also answered questions about their family, school, and friends.

What they found: The farther along kids were in puberty, they more likely they were to have used or abused substances. Age and grade seemed to also predict the chance of using and abusing substances—until the researchers controlled for puberty and the link vanished in the case of grade and became much weaker for age. But early maturers weren't any more likely to use substances—it just looked that way because they'd been in the danger zone longer.

What the study means to you: The researchers also confirmed that connections to family and school reduce the chances adolescents will use and abuse drugs and alcohol—and having best friends who use substances increases the risk.

Caveats: The students rated their own pubertal development to avoid the embarrassment of having physicians check them out. The method they used is supposed to be pretty solid, although more so for girls than for boys.

Find out more: A fact sheet from the American Academy of Pediatrics on preventing teen drug use

Read the article: Patton, G. C., et al. "Puberty and the Onset of Substance Use and Abuse." Pediatrics. September 2004, Vol. 114, No. 3, pp. e300–e306.

Abstract online: http://pediatrics.aappublications.org