Sean Rossman

USA TODAY

Ask an expert about the effects of marijuana withdrawal and the conversation quickly turns to the cognitive.

After all, marijuana is a hallucinogenic drug that alters the brain, how a person thinks and perceives the world, research shows. Experts then can identify with actor Woody Harrelson and his decision to quit marijuana a year ago because it kept him from "being emotionally available."

It's true. Real feelings are among the things that return to a person coming off years of marijuana use. But so does anxiety and the realization of the drug's consequences.

Dr. Stuart Gitlow, a professor at the University of Florida and a past president of the American Society of Addiction Medicine, and Caron Treatment Center Medical Director Dr. Joseph Garbely walked us through what happens when a person stops smoking marijuana.

They miss and crave it at first

Gitlow claims one of the issues people experience when they stop using marijuana, is the act of stopping using marijuana.

"There's a familiarity with an experience that now will be missed," he said.

He described it as being married to someone you don't like, then missing them once you divorce them.

They get anxious

Garbely said with the cravings come anxiety.

Upon quitting, a person could be unhappy, irritable, anxious and jittery, said Gitlow, along with a longing to make things go back to the way they were.

They feel feelings again

After the anxiety comes the true emotions, which often aren't good ones.

Rather, they tend to revolve around the consequences that caused them to quit: Dysfunctional relationships, performance at school or work, the time wasted doing the drug and the realization they aren't cognitively what they used to be. Marijuana has been linked to a change in IQ.

"The desire to numb bad feelings come at the cost of numbing good feelings," Garbely said.

It's going to be uncomfortable for months, even a year

The withdrawal of any drug, Garbely said, will produce the opposite feelings of what the drug produced

The consistent hallucinating of your brain, Gitlow said, damages a person's perception. Done day after day, a person finds themselves acclimated. So when the person stops using, it's going to cause them to feel uncomforabtle, even if they do objectively feel better.

"If I've been damaging your perception and you have acclimated yourself to that, and now i take it away, you're going to feel worse," Gitlow said.

Gitlow said it could be months and up to a year before a person gets used to their new reality.

Gitlow stressed it will take "many years" to know the pulmonary effects of today's marijuana. However, data supports its ability to change how a person thinks.

"There's no safe level of use," he said. "We look at it as a much more dangerous and insidious drug."

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Follow Sean Rossman on Twitter: @SeanRossman