Smokers trying to quit start getting the crazies within the first 30 minutes of quitting, according to a new study that likely confirms what most smokers already knew.

Nicotine-withdrawal symptoms, which include cravings for cigarettes, mood disturbances, appetite increase and sleep problems, are signs of a smoker's body and mind adjusting to being without the stimulant.

These symptoms peak within the first three days of quitting, but can last for two weeks or longer.

The researchers studied 50 people who smoked one pack a day and randomly selected half of them to continue smoking as usual, while the other half were deprived of cigarettes.

Within half an hour, those who were not smoking reported cravings. In an hour, they were angry.

Within three hours, they were anxious, sad, and had trouble concentrating, all symptoms that generally drive a potential quitter to smoking again, researchers report in the current issue of the journal Psychopharmacology.

"This study suggests that the typical smoker begins to feel somewhat out-of-sorts within an hour of his or her last cigarette," said lead author Thomas Brandon, director of the H. Lee Moffitt Cancer Center & Research Institute's Tobacco Research & Intervention Program. "Although they are not yet in the throes of full withdrawal that they would experience after a day without nicotine, they can already perceive that they are not feeling quite right, and that a cigarette would offer temporary relief."

Smokers seek this temporary relief by smoking as soon as the effects of the last cigarette have left their brains. They average one cigarette about every 40 minutes, Brandon said.

According to the American Lung Association, of the current 44.5 million American smokers, more than 32 million reported in a recent survey that they wanted to quit smoking completely.

Smoking-related diseases kill approximately 438,000 people in this country each year.

"The study indicates that nicotine withdrawal is not only a barrier to quitting smoking, but that it likely plays a subtle role in the decision to smoke nearly every cigarette of the day," says Brandon. "Nicotine replacement [such as nicotine gum or lozenges] may help you get through the day, but really, this is another good reason to quit smoking all together and enjoy life without the daily burden of nicotine withdrawal."

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