CU Expert Says Marijuana Increases Risk Of Severe Mental Illness

DENVER (CBS4) - "I quit recently and I was doing it almost every day for seven years," said a woman with two children. She was one of those CBS4 asked about marijuana's effects. "I don't think it hurt me in the long run. I don't think it was bad for me … I passed my tests, I still went to class and did what I had to do."

But she did stop. And she is unsure of what she will tell her children when they're older about its safety.

"I would just encourage my kids not to smoke," she said.

Tetrahydrocannabinol, or THC, is a fat or lipid soluble substance that can remain in the body for some time. Experts know a few things -- and don't know a few things, especially about long-term effects.

Ultimately marijuana raises levels of cannabinoids.

"Basically it contains what are called cannabinoids and your brain has a lot of them," said Dr. Christian Hopfer, a psychiatrist with the University of Colorado's School of Medicine.

The brain has receptors for various substances.

"Tobacco acts on the niccotinic receptor, cocaine acts of the dopamine transporter, cannibinis acts on the cannabiods, opiates act on the opiate receptors," Hopfer said. "You're using them all the time to regulate your appetite, pain sensation, anxiety, and learning,"

The cannabinoid system is used to create memories. That's why the formation of memories can be impaired. But like a lot of things with the human body, there's some amount at which there's too much.

"If you keep using it over time, your body's own natural ability to produce its own cannabinoids sort of goes down," Hopfer said.

Addiction is more likely for someone who starts smoking pot at a young age. Still it takes years -- perhaps a decade to create addiction. There is a social effect of addiction, according to Hopfer.

"You might still be able to function in your job, but a lot of your time and energy is spent on smoking and you're just not doing other stuff. And there may be some subtle impairment of your ability to learn or other things. It's not maybe as dramatic as you would expect with other substances," he said.

In spite of the fact that pot has been smoked for decades in the U.S., there's been little real long-term data. There is one big mystery: "What's not appreciated by the public is that there are a lot of studies showing that there's an increased risk of severe mental illness," Hopfer said. CBS4 asked, why? "They don't know."

It's been found rarely -- about one in 1,000 smokers, but it has been uncovered.

"It's not a big risk, but it does appear that in some vulnerable people marijuana can cause a real, serious mental illness, like a psychotic condition that persists."