TEEN MARIJUANA USERS MORE LIKELY TO GET DEPRESSED

Study Finds Daily Smokers More Susceptible To Anxiety As Adults

Teenagers who smoke marijuana on a daily basis cause damage to their
developing brains, making them more susceptible to depression and
anxiety in adulthood, a new McGill University study suggests.

The finding is particularly significant in the Canadian context, given
previous research showing that more teens in this country consume
cannabis than do adolescents in the U.S. or Europe.

"Just because marijuana is a plant doesn't mean it's harmless," said
Gabriella Gobbi, one of the study's co-authors.

"Our study demonstrated that the cannabinoid, when consumed daily
during adolescence, can induce a permanent change in the brain."

Scientists at the Research Institute of the McGill University Health
Centre experimented on adolescent and adult lab rats. They discovered
that when they exposed the rats for 20 days to cannabinoids -- the
active ingredient in marijuana -- only the adolescent rats were
adversely affected. This suggests that the adolescent brain -- since
it is still developing -- is particularly vulnerable to chronic drug
use.

The researchers observed a decrease in serotonin levels in the brains
of the adolescent rats. Serotonin is a neurotransmitter that plays a
role in emotional perception.

Conversely, the researchers noticed an increase in norepinephrine
levels. Norepinephrine plays a key role in the so-called
fight-or-flight response, and increased levels could make one more
anxious.

The findings were published in the journal Neurobiology of Disease.
Although the research was carried out on lab rats, Gobbi said one can
assume the same effects on the human brain. Still, Gobbi plans to
carry out a different type of study on humans to confirm the effects
of the animal trials. Gobbi cited research by the Public Health Agency
of Canada in 2004 that showed that 42.7 per cent of Canadian
adolescents had tried marijuana compared with 40 per cent of teens in
the United States and 35 per cent of teens in Europe.

Earlier research by Gobbi has also challenged some of the myths
surrounding marijuana. In 2007, she published a study that found that
although marijuana does act as an anti-depressant in the short-term,
it produces the opposite effect in the long run.