75A - PH - MEDICAL MARIJUANA - PROHIBIT

Home Browse Search

"Adolescents in particular should never take cannabis -it's far too risky because the brain areas essential for behavior and cognitive functioning are still developing and. are very sensitive to drug exposure," says Jasmin Hurd, who led the study at the Karolinska Institute in Sweden. But Hurd acknowledges that most people who use cannabis begin in their teens. A recent survey reported that as many as 20% of 16-year-olds in the US and Europe had illegally used. cannabis in the previous month. "Teenage" rats. In order to explore how the adolescent use oFcannabis affects later drug use, Hurd and colleagues set up an experiment in rats aimed to mirror human use as closely as possible. In the first part of the trial, six "teenage" rats were given a small dose of THC -the active chemical in cannabis -every three days between the ages of 28 and 49 days, which is the equivalent of human ages ] 2 to 18. The amount of THC given was roughly equivalent to a human smoking one joint every tlu-ee days; Hurd explains. A control group of six rats did not receive THC. One week after the first part was completed, catheters were inserted in all i2 of the adult rats and they were able to self-administer heroin. by pushing a lever. "At first, all the rats behaved the same and began to self-administer heroin frequently," says Hurd. "But after a while, they stabilized their daily intake at a certain level. We saw that the ones that had been on THC as teenagers stabilized their intake at a much higher level than the others -they appeared to be less sensitive to the effects of heroin. And this continued throughout their lives." Hurd says reduced sensitivity to the heroin means the rats take larger doses, which has been shown to increase the risk of addiction. The researchers then examined specific brain cells in the rats, including the opioid and cartnabinoid receptors. They found that the rats that had been given THC during adolescence had a significantly altered opioid system in the area associated with reward and positive emotions. This is also the area linked to addiction. "These are very specific changes and they are long-lasting, so the brain may `remember' past cannabis experimentation and be vulnerable to harder drugs later in life," Hurd says. Neurologist Jim van Os, a cannabis expert a.t the University of Maastricht in the Netherlands told New Scientist the research was a welcome addition to our understanding of how cannabis affects the adolescent brain. "The issue of cross-sensitization of cannabis/opioid receptors has been a controversial one, but these findings show the drug's damaging effects on the reward structures of the brain," van Oshe says. "There i.s now overwhelming evidence that nobody in the brain's developmental stage -under the age of 21 -should use cannabis." The research appears in the online edition oi'Neuropsychopharmaeology. Source: httg:/Iwww.newscientist.com/channel/heal.th/dn94K8-why-teenagers-should- steer-clear-of-cannabis.htm l Cannabis link to mental illness strengthened 23:01 21 November 2002 NewScientist.com news service Emma Young The link between regular cannabis use and later depression and schizophrenia has been significantly strengthened by Three new studies. The studies provide "little support" for an alternative explanation -that people with mental illnesses self-medicate with marijuana -according to Joseph Rey and Christopher Tennant of the University of Sydney, who have written an editorial on the papers in the British Medical Journal, l7 75A-91