Marijuana is a plant-based drug capable of producing significant abuse- or addiction-related problems, known collectively as symptoms of a condition called cannabis use disorder. People who smoke marijuana have unusually high chances of being affected by major depression or other forms of depressive illness. In a study scheduled for publication in April 2014 in the journal Addictive Behaviors, researchers from the University of California, San Diego sought to determine if depressed marijuana users have a harder time quitting the drug than users unaffected by depression. These researchers also looked at the cessation-related impact of a precursor symptom to mental health problems called serious psychological distress. The Basics Roughly one of every 11 people who start using marijuana will develop the physical\/psychological signs and symptoms of drug addiction. Seriously elevated risks for addiction-related problems occur in anyone who uses the drug on a daily basis. Whether they use marijuana occasionally or regularly, teenagers and preteens also have unusually elevated chances of encountering addiction-related issues. In addition, teen and preteen users of the drug put themselves at risk for developing highly entrenched forms of addiction. Federal law prohibits the sale and use of marijuana throughout the U.S. However, since the mid-1990s, more than a third of all U.S. states (as well as the District of Columbia) have passed laws that make it possible for adults to use marijuana as a medical treatment for various ailments. As of 2014, two states (Washington and Colorado) also have laws that make it legal to use small amounts of the drug for non-medicinal purposes. Overlap with Depression In addition to major depression, depressive illnesses recognized by the American Psychiatric Association include dysthymia (persistent depressive disorder) and disruptive mood dysregulation disorder. Marijuana use probably doesn\u2019t directly increase the chances that a given individual will develop depression-related symptoms. Nevertheless, depression and marijuana intake still appear together with notable frequency. Possible explanations for this overlap include similarities between the genetic risk factors for depressive illness and drug use, similarities between the environmental risk factors for depressive illness and drug use, and the potential for marijuana use to strengthen any given person\u2019s latent tendencies toward depression and psychosis, a highly disorienting grouping of symptoms that sometimes accompanies depression. People who habitually smoke marijuana or take unusually large amounts of the drug appear to experience depression symptoms more often than casual or occasional users. Difficulty in Quitting In the study published in Addictive Behaviors, the UCSD researchers used information from the 2011 version of a nationwide project called the National Survey on Drug Use and Health to assess the difficulty that depressed people have when attempting to quit using marijuana. The chosen sample of participants from this project included 39,133 adults not hospitalized for substance-related issues or any other health problems. In addition to quitting success, the researchers looked at aspects of marijuana use such as frequency of intake and the presence of any abuse- or addiction-related problems. In addition to diagnosable symptoms of major depression, they examined the frequency of symptoms of serious psychological distress, a partially impaired mental state that can set the stage for depression and a range of other mental illnesses. The researchers confirmed that, compared to adults unaffected by depression, depressed adults have substantially increased chances of ever having used marijuana, having used marijuana in the previous year, using marijuana frequently and developing marijuana-related problems with drug abuse and drug addiction. In addition, they concluded that, compared to people unaffected by serious psychological distress, individuals affected by this mental illness precursor also have increased odds of appearing in all of the same categories. When it comes to quitting marijuana use, the researchers concluded, adults affected by major depression or serious psychological distress make attempts to fully suspend their intake or curb their intake at least as often as adults unaffected by these problems. However, they succeed in their cessation and limitation attempts significantly less often than their depression-free and psychological distress-free peers. Out of all groups under consideration, those recently affected by a bout of major depression had the least success when attempting to quit using marijuana or decrease their drug intake. People with a past history of major depression experienced fewer difficulties than the recently affected, but still had a lower rate of success than those not impacted by depressive illness. Significance Based on their findings, the authors of the study published in Addictive Behaviors believe that programs designed to help people stop smoking marijuana must take their participants\u2019 recent and past experiences with major depression and serious psychological distress into account in order to achieve their desired large-scale results.