The weed on today's streets is not the same stuff your parents used to smoke. In fact, it may not even be the same as what your older siblings or cousins used to smoke.

According to a brain development researcher in London, Dr. Elizabeth Osuch, street marijuana has changed drastically over the past 10 years.

Marijuana contains a number of active ingredients, but Osuch's research focused on two main components: Tetrahydrocannabinol (THC) and Cannabidiol (CBD). THC gives users the "stoned" feeling associated with being high, impairs reaction time and destabilizes brain function. CBD stabilizes the THC, stabilizes brain function, does not impair p er formance and appears to reduce anxiety.

After looking at a 25-year study of marijuana seized by London police, the results were clear. "The THC concentration is increasing," Osuch said.

Higher levels of THC in marijuana produce a stronger, clear-headed and energetic high.

"It's also very destabilizing to the brain," cautioned Osuch. "(It) can lead to problems because of that. In addition, CBD is decreasing." CBD, she explained, stabilizes the effects of THC.

Hans Serif (name has been changed) has been smoking marijuana for 11 years. "When I started, I smoked a few times a week at most. Though I smoke about as frequently now, most of the years in between saw me as a very casual smoker, perhaps only a couple of times a year. Now I might smoke a few times a week, but with consideration to my schedule and those around me."

He said it is "absolutely true" that he has noticed a change in the effects of marijuana since he began smoking. "I haven't studied it, by any means, but there's a considerable difference between generations of weed."

Osuch said increased levels of THC in marijuana may be due to natural selection. "People like the stuff that gets them more stoned … so that's what the growers create. It's the same way apples and roses and pears are all created genetically by keeping the ones you like and destroying the ones you don't like."

Serif began smoking when he was 18 years old. According to Osuch, Serif was just above the age where marijuana could have had a serious effect on his brain development.

"There are studies out of the Netherlands in particular, where marijuana is legal and therefore it's easier to study regular users, that demonstrate that frequent marijuana use — particularly in youth — is an independent risk factor for schizophrenia, bi-polar disorder, depression and some anxiety disorders. Essentially what you're doing is you're increasing your risk of getting a serious psychiatric disorder. It doesn't mean you will get it, but the probability increases that you will."

Serif said he agrees with this idea to a certain extent, but added, "Psychiatric episodes have so many potential causes that I would think it difficult to villainize pot ... psychology is governed by so many variables, I don't think it's possible to have all of the answers."

Osuch contended that marijuana does have some beneficial effects — "There are some studies that show it's helpful with pain and nausea." But she did add, "It's very important to note that those studies did not use current street marijuana; they used medical marijuana. The maximum concentration of THC (in medical marijuana) is about 10 per cent or less." According to Osuch, street marijuana contains a THC content of about 20 to 30 per cent.

With increased use of any drug comes the danger of addiction. Psychologists cannot officially term people who are dependant on marijuana as being addicted, however, "I've seen people who are addicted to it," Osuch said matter-of-factly. "Quite a number of them."

"We don't use the term 'addiction' anymore — we use 'dependence,'" she went on to explain. "What that means is that the person needs a greater quantity of the same substance to get the same effect … They don't feel right unless they get more and more of it."

"If that's the only way you can be happy, you're setting yourself up for some problems."

Osuch said that users who try to cut back on their weed use may experience some withdrawal symptoms, including irritability, anxiety, physical tension, decreases in appetite, stomach pain, restlessness, insomnia, increased aggression or anger.

There is help in the community available for those who are considering quitting marijuana, or any other substance. Visit the Addiction Services of Thames Valley's website at www.adstv.on.ca for more information.