Corrected on 5/9/08: An earlier version of this story misspelled the name of Bruce Mirken.

Today the White House Office of National Drug Control Policy sent out a clear message on teen pot use and depression: They're a bad combination. Issuing a report that analyzes around a dozen studies about marijuana use and mental health, the policy office warned that teens who use marijuana to "self-medicate" may worsen their underlying depression or other mental health issues. The intention of the report, says John Walters, director of the Office of National Drug Control Policy, is to "try to correct two misunderstandings: That teen depression is not a problem and that teen marijuana use is not a problem—marijuana use is not safe." He advises parents to talk to their kids' pediatrician if they see signs of depression and suspect drug use.

The report, entitled "Teen Marijuana Use Worsens Depression: An Analysis of Recent Data Shows 'Self-Medicating' Could Actually Make Thing Worse," cites statistics to support its warning message, but experts are quick to note that it should be interpreted with caution. For example, the report's statement, "One 16-year study showed that individuals who were not depressed and then used marijuana were four times more likely to be depressed at follow-up," suggests marijuana might cause depression. That data from a 2001 study in the American Journal of Psychiatry was only statistically meaningful after the researchers adjusted for variables including age, gender, and antisocial symptoms, suggesting a weaker relationship between depression and marijuana before adjustments were made.The study also showed that those who were not depressed when first surveyed and then used opioids were 228 times more likely to be depressed at follow-up—without any adjustments. That statistic was not mentioned in the Drug Control Policy's report today. "Adolescent marijuana use may be a factor that triggers psychosis, depression, and other mental illness," says Walters, acknowledging that "research about causality is still ongoing."

Policy groups on the other side of the aisle believe the report is misleading. "We agree that kids shouldn't smoke marijuana, but we simply have to be honest to teens and parents. This report [is] deliberately confusing correlation with causation," says Bruce Mirken, director of communications at The Marijuana Project , a Washington-based group that aims to remove criminal penalties for marijuana use and make medical marijuana available to seriously ill patients with doctor's approval. "This very week the British government's official scientific advisors on illegal drugs issued a report saying they are 'unconvinced that there is a causal relationship between the use of cannabis and any affective disorder,' such as depression." Mirken takes issue with the lack of warning about alcohol's relationship to depression. "Data linking alcohol to depression is much stronger and alcohol use by teens is greater than marijuana use," he notes.

To be sure, experts believe marijuana carries risk, especially in the subset of teens who are more susceptible to substance abuse and mental health problems due to genetic makeup or environmental factors. "Among treatment populations [in] youth with substance abuse, there's a pretty high rate of clinical depression," says Oscar Bukstein, associate professor of psychiatry at the University of Pittsburgh School of Medicine; "many kids get high not to stay low."

Perhaps most important, those people with co-existing substance abuse and a mental health disorder have worse outcomes than those with either problem alone, he adds. For perspective, Bukstein notes that research has shown 1 in 10 kids who smoke marijuana go on to develop dependence, and about 1 in 10 kids who become dependent on marijuana have psychotic symptoms.

The bottom line, says Bukstein, is that mental illness and substance abuse very often go hand-in-hand. Parents who spot signs of depression should have their child professionally assessed for mental health issues, he says, and also for substance abuse—and the reverse is also true. As part of their development, kids are curious (see our previous story on teens' questions about drugs, addiction, alcohol and the like). To lower the likelihood of experimentation with pot, he advises parents to:

Always monitor and supervise. Know where your kids are going and with whom.

Set limits. Be sure they're not hanging out in homes where no adults are present.

Be consistent. Discipline works only when it's reinforced.

Seek professional help. If you have a hunch something's wrong, you're probably right.