Teens Who Smoke Pot at Greater Risk For Schizophrenia

Marijuana is the most-used recreational drug in the world, a substance generally viewed as much less harmful than drugs like cocaine or heroin. But a new documentary reveals that heavy marijuana use at an early age could be damaging to young minds and even cause schizophrenia.

The Downside of High examines startling new research that teens who start smoking pot before the age of sixteen are four times more likely to become schizophrenic. The documentary (premiering on CBC's The Nature Of Things tonight -- Thursday, January 28th -- at 8PM, and repeating on CBC News Network on Thursday, February 4th at 10PM ET/PT) highlights the latest findings by some of the world's top schizophrenia experts. In addition to the danger faced by young teens, the doc reveals that for all young adults, smoking pot doubles the risk of developing psychosis, paranoia and hallucinations, the hallmarks of schizophrenia.

"Ever since it was introduced in the 60s, people have felt that it is a relatively harmless drug," says Bruce Mohun, the film's director and writer. "And for many people it is. But this research is saying, no, there is potential harm here, a very serious potential harm for a small amount of people who have susceptibility to schizophrenia."

Find out if your child is at risk, after the jump...

The documentary profiles three Canadian young people who experienced psychotic episodes and were diagnosed with mental illness (two with schizophrenia, one with bipolar disorder). All suffered debilitating symptoms of hallucinations and anxiety and spent months in psychiatric wards. In all three cases, doctors believe their mental illness was triggered by their heavy pot use.

As revealed in the documentary, the problem seems to be the super-potent marijuana that has been developed by growers in recent years. The percentage of THC (Tetrahydrocannabinol) in pot has been going up steadily in the last 30 years, as growers attempt to breed marijuana with a stronger high. For example, Health Canada found THC levels of 4.8 percent in marijuana confiscated in 1988, whereas the average level was 11.8 percent in marijuana confiscated in 2008. And one of the by-products of developing such high levels of THC has a dangerous consequence: While the THC goes up, the level of cannibidiol, an ingredient which appears to buffer the effects of THC, goes down. So it's a double whammy for young people smoking pot today: They are getting very high levels of THC, and very low levels of the protective cannibidiol.

But why are teens particularly vulnerable? Scientists in the film compare a teen's brain to a messy bedroom. It's a jumble of circuits that needs to go through "neuro-pruning," an essential streamlining process. Scientists feel that marijuana interferes with the brain's ability to neuro-prune and can produce devastating, long-term results. And the stronger the pot, the more damage to the developing brain.

"Although puberty lasts four or five years, the brain's development continues until they are 24 or 25," says Mohun. "So that brain is affected by whatever kind of drugs you put into it. Schizophrenia is a young person's disease, it tends to show up between the ages of 14 and 25."

Is Your Child at Risk?
Mohun says it's important to point out that many people will smoke marijuana and have no psychotic symptoms at all, and marijuana cannot cause schizophrenia on its own. But how can parents know if their child is at risk? Researchers have identified several risk factors for the development of schizophrenia, including a family history of psychosis, the use of "upper" drugs like cocaine or meth, childhood trauma, living in a city (since urban dwellers have a higher rate of schizophrenia than those in rural settings) and a "psychosis-prone" personality (a child who may exhibit odd behaviour or has trouble relating to other kids). Scientists have been honing in on a genetic marker for schizophrenia, but the film points out that any test to identify who may be most at risk for developing marijuana-induced psychosis is at least 10 years away.

Dr. Robin Murray, one of the world's leading experts on schizophrenia and a professor at the Institute of Psychiatry in London, England, says in the film, "The problem with cannabis is that you have those on the one hand that say it's a sacred herb, and on the other extreme you have people that say cannabis is the work of the devil. But neither of these extremes is practical. What we need is a situation where people know that if you smoke cannabis heavily, particularly if you smoke the potent brands of cannabis, then you're more likely to go psychotic".

The film also raises the possibility of legalizing marijuana to combat the problem. The theory is that if marijuana were regulated (like alcohol for example), the balance of THC vs. cannibidiol could be kept in check, and so young people wouldn't be exposed to the much more dangerous, stronger pot.

"But the the drug will never be legalized for kids under 18," says Mohun. "And then the question is, are the kids under 18 going to have less access to it if it's legalized, or more? However, even if it they do have more access, they'll have access to a less harmful drug."