Adolescents who smoke marijuana could be at risk for a drop in IQ, as a new study links heavy marijuana usage in teenagers with cognitive decline. The study, published in the “Proceedings of the National Academy of Sciences” at the end of August, found an IQ decline in 5 percent of teen users with a loss of up to eight IQ points.

The study is being called the first of its kind because of its long-term examination of IQ before and after routine use of the drug.

“That was the first one I looked at that looked specifically at adolescents, at least as far as IQ,” said Dan McCune, pharmaceutical sciences professor at Wilkes.

The study is bringing attention to some of the known negative effects of marijuana usage, as well as what is still unknown about the drug’s effects.

While knowledge on the consequences of the drug has been increasing, so have the statistics on usage. 17.4 million Americans 12 years old or older reported using marijuana at least once in the previous month, according to the 2010 National Survey on Drug Use and Health.

This high number of usage may be a driving factor behind these new studies. The IQ study was groundbreaking not only for the subject matter, but for the unprecedented indication of permanent cognitive effects. McCune explained he has seen past studies showing a drop in IQ for adults, but the effect was always temporary and could be reversed after about a month.

“The fact that there’s an IQ drop isn’t surprising,” McCune said. “The surprising part and the concerning part is that it’s apparently permanent.”

Psychology professor Edward Schicatano, who teaches classes on neuroscience and how drugs affect the brain and behavior, agrees that this is the most alarming part of the study. He said the connections between neurons in the brain are usually only affected while the drug is in the system.

“It might be temporary while the drug’s in the system or there might be just a little bit of the way the neurons are connecting, but that can grow back,” Schicatano said. “If you start learning again, the neurons will reconnect, and that’s typically what happens. I didn’t know this, that it’s permanent and that’s the first I’ve seen that.”

He said the findings are alarming because they may indicate that the drug is killing cells in the brain.

“As far as this being a long-term effect on IQ … That does imply that it’s killing cells, or at least the connections between nerve cells,” Schicatano said.

But McCune said he was not surprised by the findings, since the drug is affecting brain connectivity at an age when changes like breakage and formation of connections is going on at a high rate.

“During that time in life, there is a great deal of changes taking place, with the neurons in the brain,” McCune said.

Shannon Gilhooley, sophomore pharmacy major, also said she wasn’t surprised to hear of the findings from what she observed in friends who began smoking marijuana in high school.

“Just knowing people who have done it seem to have a lower IQ,” Gilhooley said. “They seem to have less ambition and don’t want to try as hard.”

This side effect of lacking ambition is actually a symptom grounded in science called amotivational syndrome, which is linked to marijuana usage. This syndrome is also often seen in depressed people.

Schicatano said amotivational syndrome may have influenced the study findings.

“If you’re not motivated to take a test, even an IQ test, your IQ is going to suffer, it’s going to be lower,” Schicatano said.

McCune said there are other potential drawbacks to the study, like that it didn’t take into account environmental and social factors.

“(With) studies of this nature, there are often outside factors like environment and psychosocial things or who knows what could’ve affected the outcome,” McCune said. “You would like to see more studies in this particular population with adolescents to see, to verify, that this is a real and permanent effect.”

Other effects of marijuana

It appears that lowered IQ is just the tip of the iceberg for side effects from marijuana usage. Schicatano said that impaired driving is something that gets a lot of attention with alcohol, but it just as dangerous while under the influence of marijuana.

“You’ve got several things that all are important for driving,” Schicatano said. “So, (marijuana is) as bad as alcohol if not worse. No doubt about it.”

Some of the things that are decreased by marijuana usage include reaction time, motor coordination, peripheral vision and visual tracking to follow something that’s moving.

“Driving under the influence of marijuana is equally dangerous, and I don’t think people really think of it that way, because marijuana does have some central nervous system depressant effects,” McCune said. “It does slow your reflexes, your psycho-motor coordination and it does impair your ability to drive a motor vehicle.”

McCune said that some of the subjective feelings, like a buzz or a relaxed feeling, wear off after about an hour, but the impairment to motor skills last much longer and users may not even realize.

An effect that lasts even longer may be the impairment of the memory system in the brain. Schicatano said the long-term damage to memory is not understood and needs more study.

“While it’s in the brain, your memory’s not good,” Schicatano said. “What are the long-term effects of that, I’m not sure.”

He said the drug affects many types of memories while in the system, and also hinders the ability to form new memories.

Another area that might call for more study is the consequences of marijuana smoke on the lungs, since there is no conclusion on the extent of damage.

“There’s been some question – and there’s no definitive proof, studies are conflicting – as to whether or not inhalation from smoke from marijuana is as dangerous as inhalation of smoke from tobacco cigarettes,” McCune said.

He said marijuana poses issues because filters, like the ones on cigarettes, are not often used and there some of the same carcinogens in tobacco present in marijuana. However, there are other factors that influence the potential for lung cancer, like the frequency of use and size of intake of smoke.

Then, there’s the misconception that marijuana is not addictive. McCune said marijuana works on the same pleasure system as heroin and cocaine do, so while it’s not to the same extent, the drug does have addictive qualities.

Schicatano said there’s potential for marijuana users to fall into a pattern of habit rather than a physical addiction, especially if the drug is used to decrease stress.

“Once you start using it to calm down, to reduce anxiety, then you can become dependent.

Schicatano said there are also positive effects of marijuana that can be applied to “special cases.” He said the drug can decrease aggression, inhibit nausea, stimulate appetite and minimize stroke damage.

However, he said in the case of a college student using the drug for recreational purposes, the symptoms like decreased motivation, reduced problem solving abilities and even a drop in IQ will only be harmful to a college career.

“To be able to function, like in college, obviously marijuana would have negative effects,” Schicatano said.