Chris M. -- who requested that his full name not be disclosed -- remembers the time in 1999 when he was caught by a security guard while smoking marijuana in a parking lot.
For him, it was a wake-up call. Chris was no teenage stoner; he was a 38-year-old anesthesiologist. But it was not the first time he had used marijuana. He started smoking pot as a teenager, and by the end of his senior year he was using it every day. Over time, his use went down, but the death of his father in 1997 led him to pick it up again.
"I learned how powerful grief was," he said.
The episode in the parking lot led Chris to rehab and a 12-step program that helped him understand the root causes of his addiction. But the experience also led to an understanding of a process more commonly associated with so-called "harder" drugs -- withdrawal.
Chris lost his appetite, had trouble sleeping, and developed body aches.
"At the time, I didn't realize it because you chalk it up to other stuff," he said. "Once I realized it and put two and two together, I talked to other people. Over time, I realized what marijuana withdrawal is."
New findings show that many people can relate to his experience. An Australian study, published Wednesday in the journal PLOS ONE, surveyed nearly 50 marijuana users on their withdrawal symptoms before, during and after a two-week abstinence period. The authors showed that marijuana withdrawal symptoms can interfere with the lives of regular users who are trying to quit.
"It's very similar to what people experience with tobacco," said study co-author Alan J. Budney, a professor of psychiatry at the Geisel School of Medicine at Dartmouth College in Lebanon, N.H. "It makes you irritable. It makes you restless. It makes it hard to sleep."
At its worst, Budney said, withdrawal from marijuana "can be very disturbing and distressing. ... It can be enough to cause you some problems at work and home."
The researchers also found that heavy users were more likely to have worse withdrawal symptoms and were more likely to relapse during the abstinence period if their withdrawal symptoms were worse. Subjects would also use much more marijuana in the following month if they had worse withdrawal symptoms.
The findings show that, contrary to popular belief, marijuana "behaves just like other drugs of abuse," said Scott E. Lukas, a professor of psychiatry and pharmacology at Harvard Medical School and MacLean Hospital in Belmont, Mass., who was not involved with the study.
"There is a common belief among the public that marijuana is not very addictive and so it is not a big problem," he said. "It is not enough to simply say, 'I want to quit,' but, instead, the person must be able to withstand the turmoil of going through withdrawal."
Dr. A. Eden Evins, an associate professor of psychiatry at Harvard Medical School in Boston, said there are certain telltale signs that accompany marijuana withdrawal. One of the most troublesome and common symptoms is an intense craving to use marijuana to get high, said Evins, who was not involved with the study.
People may "seem moody, tense, anxious and nervous," she said. Other symptoms include an inability to sleep, a loss of appetite and difficulty sitting still.
The symptoms usually peak at around four days and last for two weeks, she said, but the extreme craving for marijuana is one symptom that can last longer than two weeks.
While the symptoms are not life-threatening, Evins said they could be very disruptive.
"It impairs people's functions," she said. "Often, it leads people to use more than they want to. Withdrawal symptoms lead people into a cycle of heavier and heavier use that impairs their functioning."
Nearly 7 percent of Americans over the age of 12 report using marijuana, according to 2009 statistics on the U.S. Centers for Disease Control and Prevention website.
For Chris, now 51, being ordered to rehab was a turning point in his life and helped him get through the turmoil of withdrawal.
"It turned out to be the best thing," he said, adding that he has been drug-free since.
His advice to those who are seeking to quit -- even though withdrawal can be a struggle -- is to avoid using marijuana.
"Don't buy any pot," he said. "Have an answer ready if somebody is going to offer it to you."