Changing laws and attitudes surrounding medical and recreational marijuana use have made the drug more accessible. Currently, 23 states in the U.S. permit cannabis for medical purposes, and four of those states have decriminalized the drug for recreational use. As a result, more people are using marijuana, and according to a new study this may come with a serious expense: Marijuana use disorders are now a bigger problem than ever.
For the study, published Wednesday in JAMA Psychiatry, researchers analyzed data from the National Epidemiologic Survey on Alcohol and Related Conditions for 2001 to 2002 and 2012 to 2013. They found that three of every 10 Americans who used marijuana in the past year had a diagnosis of a marijuana use disorder, a condition in which a person becomes dependent on the drug and uses it daily in excess, sometimes at the expense of taking part in other activities. This adds up to approximately 6.8 million people. Between 2001 and 2013 overall marijuana use rose from 4.1 percent to 9.5 percent. So while the overall rate for addiction and dependence has gone down in the last decade—from 35.6 percent in 2001–2002 to 30.6 percent in 2013, there is a larger population of users who are now addicted to the drug, because of how many more people have access.
The data showed an uptick in the number of women and people who are black and Hispanic using the drug. The researchers also noted an increase in cannabis use among middle-age adults and people living the Southern region of the U.S.
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“Clearly not everyone is at risk for those problems but this risk is there,” says Dr. Deborah Hasin, a professor of epidemiology at Columbia University Medical Center and lead author on the paper. “Research that could help us to identify what causes people to be vulnerable would be useful.”
Marijuana is viewed by many people as a harmless and nonaddictive drug. But while the long-term effects of frequent use probably aren’t as detrimental as other substances such as heroin, experts say the drug can become addictive. Dr. David Sack, chief medical officer of Elements Behavioral Health and Promises Addiction Treatment Center in Long Beach, California, says that the idea that marijuana dependency doesn’t occur is a myth. “It has a very predictable set of withdrawal symptoms. It usually starts in 48 hours and peaks within 7 days,” he says. These symptoms include dysphoria, insomnia, anxiety and cravings for the drug.  Those who try to quit frequently relapse, and sometimes a person who is misusing marijuana may also struggle with addiction to other substance.
The drug also functions differently in the body than other substances. Marijuana is stored in fat tissue, which means it stays in the body for about 30 days, says Sack. To compare, heroin only maintains a presence in the body for about three minutes, while the liver processes one serving of alcohol in less than one hour. Sack says the notable personality differences in marijuana users are due to the fact that the drug remains in the system long after a joint has been smoked.
In his own practice, Sack has seen a noticeable increase in number of patients who have use disorders since California changed its laws around medical and recreational cannabis. He particularly worries about the older population of baby boomers who had positive experiences with the drug in the 1960s and 1970s. “They’re much more likely to use it today," he says. “They’re familiar with the drug, they’re not afraid of it. I think we have to increase awareness in the general medical community to identify the addiction and to start asking about marijuana use.” 
Sack says that currently there aren’t any specific treatment programs to address marijuana addiction. For his patients, Sack frequently turns to cognitive behavioral therapy, which is a tool used to address other substance addictions. He may also prescribe certain medications for short durations of time to alleviate some of the symptoms that come with stopping marijuana. These may include fast-acting anxiety drugs like benzodiazepines or antidepressants.