Victoria Costello

Posted January 14th

In last month's holiday rush, you may have missed the bad news on 2009 trends in American teenage drug use. According to the University of Michigan's annual Monitoring the Future Survey, marijuana use by American adolescents, especially eighth and tenth graders, is trending upward for the third year in a row, reversing a decline tracked since 1992.

Two other even more worrisome trends were reported in the survey. The age of first time marijuana users is dropping, and fewer teenagers believe there are health risks associated with their use of marijuana.

That these trends are present when so much existing scientific research points to the complicity of marijuana in triggering first episodes of psychosis in teenagers is terrifying. Or it should be.

One possible reason for the apparent widespread ignorance by teens (and their parents) may be the media's general failure to distinguish between adolescents and adults when they report on marijuana use and its dangers. This type of oversimplified coverage has increased as medical marijuana is legalized in some states, and as state and local campaigns rev up to give marijuana the same legal status as alcohol.

Before we jump into pro or con camps on such issues, it behooves us to take a closer look at the science. It is true that the relative numbers of teens who smoke pot and develop psychotic symptoms is relatively low; in some studies it's put at 3 percent. But the risk then goes up to 10 percent or higher for those teens who are at a genetic risk for psychosis, that is, those who had a relative with a psychotic disease like schizophrenia or bipolar disorder.

Which brings us to the other equally large obstacle for anyone personally trying to confront this issue. How are parents to assess their teenager's risk when they don't know their own family mental health history?

The reason for this lack of basic information about our ancestors, i.e., parents, grandparents and great-grandparents mental health has everything to do with the centuries' old stigma associated with mental illness. Plus, the lack of proper diagnoses and treatment for these illnesses which while not so great today was far worse in past generations.

Not having this information necessarily turns us into amateur forensic psychologists. Was your great aunt's fear of leaving the house just eccentricity? Was grandpa's death at 28 really an accident? Or may there have been other factors at work in these or other dark family episodes that have been largely swept under the rug. But what if your child's health and welfare were at stake?

I can offer my first hand experience with the dangers of not knowing.

It began ten years ago, when I sat across the desk from my then eighteen year-old son Alex's psychiatrist. Early that morning Alex drove my car into the fence of the high school parking lot...but then couldn't explain to the arresting officer why he'd done it.

I should say here that I knew my son was having emotional and legal troubles; he'd been in and out of three high schools, and in therapy for the past year. But what I heard next was the worst possible news.

"I have completed my diagnosis of Alex," the psychiatrist began. "He has paranoid schizophrenia. His condition is complicated by his recent use of marijuana and met amphetamines, but the underlying symptoms of paranoia and schizophrenia are clearly present."

The next day, I related Alex's diagnosis to Alex's psychotherapist, Steve, who came by the hospital to visit him in the ward.

"No way," Steve said. "They're missing the impact of the drugs. His psychotic symptoms are temporary and drug-related."

How I wanted to believe Steve, but I was also terrified of staying in denial about Alex's condition any longer. It would take another two years before I'd amassed the personal family history to help me understand that at the time he started heavy use of marijuana and speed, Alex was in a high risk group for psychosis, making his recreational use of these drugs akin to playing a game of Russian roulette-with a loaded gun.

Sadly, I can say with a high degree of confidence that this same awful but preventable experience is being repeated by parents and their teenage children in ER's and doctor's offices throughout the U.S. (and world) right now.

After it happened to me, I started looking for answers from those researchers who were studying the problem close up.

"Cannabis is definitely part of the cause of schizophrenia," Irish brain researcher Dara Cannon told me in the summer of 2009 when we spoke in her native Galway. After starting her career in the U.S. at NIMH, then working in London and New Zealand, this city on Ireland's west coast is where Cannon currently directs a state-of-the art brain imaging institute.

In making her surprisingly unequivocal statement linking schizophrenia and cannabis Cannon was drawing on work she'd done in the mid-nineties as an investigator in a New Zealand-based study of the illegal drug habits of at risk youth.

In that study, Cannon found that smoking cannabis before the age of 15 increased the chance of schizophrenia developing in high risk youth from 3% to 10% by age 26. Her study concluded that there are a minority of teenagers, a group which no doubt had included Alex, who, because of their genetic loading will always be highly vulnerable to cannabis.

Cannon's finding in New Zealand has since been corroborated by evidence gathered in several other countries, including Greece, where researchers found that children with disturbed thought processes at age 11 were at a 25% risk of psychosis if they didn't go on to take cannabis, but a 50% risk if they did use it.

Cannon offered this information in response to a question I asked about how parents can determine whether their kids are at high risk, especially when the ancestor they suspect may have been mentally ill was never diagnosed. After confiding her own personal story of a great aunt's undiagnosed bipolar disorder, Cannon said she understood the difficulty of dealing with such issues in families. As we stood on a sidewalk by the Galway bay saying goodbye, Cannon, who recently gave birth to her first child, a girl, returned to the subject once more, saying, "With my family history, I'll do anything I need to so I can keep my daughter away from the stuff."

Hearing this, I wondered what I might have done differently after finding pot hidden in Alex's bedroom when he was 14 had I had known how dangerous it was going to be for him. Certainly, I got angry. I grounded him for a month. But, to be honest, at the time I thought Alex's marijuana smoking was the least of our problems. More troublesome, I thought, was the fact that he hadn't done his homework in recent memory.

I tell the larger story of my family experience with mental illness in my upcoming science memoir, A Lethal Inheritance.

My message for parents: know your family mental health history and learn about the latest research on early signs and prevention of mental illness in your children.

For more information on the 2009 University of Michigan MONITORING THE FUTURE SURVEY GO TO: www.monitorthefuture.org

For more mental health information for families and individuals go to the NIH and NIDA government websites.