Aug. 5, 2009 -- Vicki, a 53-year-old former rock promoter married to a stand-up comic, started smoking weed when she was just 13.

"I had an older brother who was already getting high, hanging out with his friends and they invited me," said the New York City mother of two teenagers. "Unlike most people, I got high the first time and fell in love."

"I was a daily smoker, 24/7 for over 30 years," said Vicki, who did not want to share her last name. "The only time I stopped was when I was pregnant. Otherwise, I was high all my adult life."

Then nine years ago, after standing on a radiator and hanging out a window to hide the smell of pot from her visiting father, she finally realized she was "an addict."

But quitting was harder than she had ever imagined. Even though Vicki rarely got the high anymore, she experienced withdrawal -- "complete sleeplessness," as well as anxiety, dry mouth, sweats and the shakes.

Since the 1970s, when marijuana was the symbol of political protest, the risks of marijuana dependency have been clouded by the legalization debate and long-held beliefs that the illicit drug is harmless.

But new thinking on old scientific research has now prompted the American Psychiatric Association to consider including "cannabis withdrawal syndrome" in its next Diagnostic and Standards Manual for Mental Disorders, due to be revised in 2012.

News Echoes 1936 Film 'Reefer Madness'

Those who have enjoyed pot for years with no ill effect, say it echoes the cult film, "Reefer Madness" that was made in 1936 when the drug was first demonized and made illegal.

In the film, high school students are depicted being lured by pushers to smoke the drug and a deadly hit-and-run accident, suicide and rape ensue.

Others, just think the new debate is a "gross exaggeration, triggered by fears surrounding the movement to legalize marijuana.

"Some research has shown that people who are heavy, regular users actually do have a physical addiction," said Herbert Nieberg, a forensic psychologist and professor at Mitchell College in Connecticut.

"There are very few cases and not more," he told ABCNews.com. "Alcohol, opiates, ocycontin and vicodin, those are the biggies."

Studies dating back to 1984 have documented a clinical syndrome characterized by "restlessness, anorexia, irritability and insomnia" that begins within 24 hours of discontinuation and can last for up to 10 days.

Today, there are no FDA-approved drugs to counteract withdrawal symptoms, although the synthetic cancer drug Marinol shows some promise.

Though withdrawal is not life-threatening, as it can be with opiates and alcohol, patients can experience high levels of anxiety, depression, become aggressive and even report referred pain, especially if they have been using marijuana to self-medicate.

"For me, the biggest withdrawal was emotional," Vicki told ABCNews.com. "I went into a total depression and severe mood swings that took a very long time to get over."

For Vicki, who confessed her long-time marijuana use to her father, it took 18 months to come clean with the support of Marijuana Anonymous.

Marijuana Dependency: Shame and Guilt

"I was 45 years old and lying to my daddy," she said. "The shame was worse than the pleasure. I was devoted to my kids, but I was the mommy in the sandbox with the sunglasses. I was leading a double life and there was constant guilt and shame."

The reclassification of marijuana is important, according to the APA because its omission as an addictive substance then professionals might not see treatment regimens for dependence as necessary.

"They are right on about that," said Tom, a Long Beach, Calif., graphic designer who has been clean for 18 years, thanks to Marijuana Anonymous.

"I was amazed at the depth of my addiction and how pervasive it was in my life," said Tom, now 53, who smoked for 19 years. "If I started up again, I couldn't put it down. It's just like alcoholics. It doesn't matter what substance it is, it's the same disease."

About 40 percent of all Americans aged 12 and older -- about 94 million -- have tried marijuana at least once, according to a 2003 survey by the National Institute of Drug Abuse (NIDA). Of those, about 3.6 million were daily users.

As the most commonly used illicit drug in the United States, marijuana produces dependence and relapse rates comparable to other drugs some researchers believe.

About 9 percent of all those who used marijuana became dependent, compared to rates of 32 percent for tobacco, 23 percent for opiates and 15 percent for alcohol, according to the 1994 National Comorbidity Survey.

For daily smokers, that dependency rate soars to between 33 and 50 percent, say more recent studies.

The drug's popularity reached its height in the 1970s among baby boomers -- about 40 percent of all high school seniors, compared with 20 percent today -- said they had smoked marijuana in the previous month, according to NIDA.

The active ingredient in marijuana that causes the "high" is tetrahydrocannabinol, or THC. Orally, THC is used to treat nausea in cancer treatment and to stimulate appetite in AIDS patients.

Cannabis Potency Stronger Than Before

Today's marijuana has far more THC than decades ago. The average potency has gone up from about 3.4 percent THC in 1982 to approximately 10 percent in 2008, according to NIDA.

With stronger pot, emergency rooms have reported more associated accidents. Just this week, seven people were killed when the driver -- drove the wrong way on a New York highway and collided head on with a pickup truck. Although the drivers family has disputed the results, toxicology tests showed high levels of alcohol and marijuana.

"The marijuana that is now out has been cross-bred like people breed flowers so what you have now is different from what you had 20 to 30 years ago," said John Massella, regional program director for the Pittsburgh-based Gateway rehabilitation center, which treats 10,000 to 12,000 patients a year.

"They develop a tolerance and need more to get the desired effect," he told ABCNews.com.

Gateway has seen an increase in number of marijuana dependency cases, mostly adults who do not come of their own volition. Many have been referred by family or have had trouble with the law or have tested positive in an employment-related urine test.

Younger Pot Smokers More Vulnerable

The younger a person begins smoking -- especially at today's higher potency levels -- when the brain is still developing, the greater the risk of dependence. "The progression is more aggressive," he said.

The biggest hurdle in treating these patients is that marijuana "still has a positive spin to it," he said. "People don't believe it's a problem."

"Plenty believe that they can't get addicted or hold on to the idea that it's only psychologically addictive and 'I can think my way out of it,'" said Massella. "But once you develop a dependency, there is always a dependency."

Such was the case with Alex, a 55-year-old Los Angeles lawyer whose life fell apart after a 39-year dependency.

"My life crashed around it," said Alex, who did not want to use his real name. "Early on, I used it to escape and have fun, but it turned into a self-medication sort of thing. Ultimately, I was using it morning, noon and night."

Hitting Bottom After Three Decades on Weed

He became sober 12 years ago after hitting bottom: His career had fallen apart, a relationship failed and he got a diagnosis of attention deficit disorder. "I had a lot of inattention, lack of focus and difficulty completing projects. Early on the marijuana helped, but then I used it more and more."

"I have a lower bottom than a lot of people," said Alex, whose parents encouraged him to seek help. He spent 11 months in rehab and joined Marijuana Anonymous. "I had my car repossessed, I was thrown from my home and I was living on a guy's sofa and I was no longer able to practice law."

"Whether it's a physical addiction or not, I was behaving like an addict," he told ABCNews.com.

"It's a complex issue," said Paul L. Doering, a professor of pharmacy practice at the University of Florida. "Many can smoke once or twice a week and not have any problems."

According to the American Psychiatric Association, a person is considered dependent if he or she meets three of seven criteria. Only two of those criteria are associated with physiological symptoms like tolerance and physical withdrawal.

All addictive drugs have a "common signature," according to NIDA director Nora D. Volkow. "They increase dopamine levels in the brain's pleasure center and produce repetitive behavior. Marijuana appears do both, though at intermediate levels compared to other drugs.

Higher Doses of Cannabis to Get Same Effect

"Social variables play an important role in humans -- we are not lab animals," she ABCNews.com. "We live in a complex social network system. Nicotine and alcohol produce lower increases in dopamine, but greater levels of addiction in society because they are legal and widely available."

Why some like Vicki and Alex become dependent and others can smoke socially, is still a mystery.

"There is tremendous variability and vulnerability," Volkow said. "It's like the H1N1 flu. Some people don't even get the symptoms and others die. It's the same thing with drugs."

"There is a tendency to try to minimize the risks associated with drugs," she said. "The one that is targeted the most in marijuana. For some, the willingness to experiment may be affected by how dangerous their perception of the drug is."

Addiction experts agree that marijuana's dangers pale in comparison to harder drugs. But distorting its risks may encourage more young people to experiment with a drug that can cause dependency.

"Marijuana has a fascinating history in part because of the hyperbole and exaggeration to either scare people so they don't use it or to justify more liberal laws," said Roger A. Roffman, a professor of social work at University of Washington, who for 20 years has studied marijuana dependency counseling. "The misrepresentations and half-truths and outright lies are really incredible."

Hard to Lick Because of Societal Views

Though Roffman favors decriminalization, he struggles to help those who are dependent on marijuana, largely because societal views lead them to "wonder if they are over-exaggerating the harm to themselves."

About 15 percent to 20 percent of those being treated for dependency in cognitive behavioral therapy or 12-step programs are able to quit and some are able to cut back, more than half "don't do very well," according to Roffman. "There's not that high a success rate."

He argues that the reform movement makes a "tragic mistake" to convince the public that marijuana is relatively harmless.

"They are not being accurate scientists and it can make a difference for those making choices about smoking," said Roffman, especially young people who are the greatest risk for "derailing" their lives.

Meanwhile, Vicki said her own children, now 11 and 15, have seen first-hand the risks of marijuana dependency. "They are very much a part of my recovery and they come to meetings. But, thank God, they don't remember me high at all."