By Amy Norton

NEW YORK (Reuters Health) - Quitting marijuana can cause withdrawal symptoms as severe as those from quitting tobacco, a small study suggests.

The study, of 12 adults who were heavy users of both marijuana and cigarettes, found that stopping either substance triggered similar withdrawal symptoms.

As with nicotine withdrawal, quitting marijuana caused symptoms such as irritability, anxiety, sleep problems and difficulty concentrating, researchers found.

"Marijuana is not as innocuous as some people would lead you to believe," said lead researcher Dr. Ryan Vandrey, an assistant professor of psychiatry at Johns Hopkins University School of Medicine in Baltimore.

Previous research had shown that there is in fact a "marijuana withdrawal syndrome," he told Reuters Health. These new findings give some idea of its significance, Vandrey explained.

It's not clear from this study whether marijuana withdrawal symptoms hinder many people from successfully quitting. However, Vandrey said that past surveys of marijuana users in treatment have shown that people with withdrawal symptoms tend to have more failed quit attempts.

The men and women in the current study, published in the journal Drug and Alcohol Dependence, used marijuana four times a day, on average, and smoked an average of 20 cigarettes per day.

None was in treatment or had any plans to quit either drug.

Vandrey and his colleagues had the volunteers go through three separate five-day periods of abstinence: one in which they quit tobacco, one in which they quit marijuana and one in which they quit both.

Across the group as a whole, the researchers found, withdrawal from marijuana was as severe as nicotine withdrawal. Withdrawal symptoms were not worse, however, when the volunteers quit both drugs at once.

The findings, according to Vandrey, should help give heavy marijuana users some idea of what to expect in terms of withdrawal.

He said other studies are looking at ways to ease these symptoms, such as treatment with an oral form of THC, the main active substance in marijuana. Sleep medication, Vandrey noted, could potentially help, since poor sleep is often part of withdrawal, but this has yet to be studied.

SOURCE: Drug and Alcohol Dependence, January 2008.

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