Anyone who uses marijuana has a significant chance of developing a diagnosable case of marijuana addiction (known technically as cannabis use disorder). As a rule, the risks for addiction rise sharply in people who use the drug every day or almost every day. In a study scheduled for publication in October 2014 in the journal Addictive Behaviors, researchers from two U.S. universities sought to determine if daily marijuana users have certain uniting characteristics. These researchers concluded that habitual users of the drug typically have a few core characteristics in common. Marijuana Users Roughly 7.3 percent of all American teens and adults use marijuana in the average month, according to recent figures compiled through the National Survey on Drug Use and Health, a yearly undertaking from the federal Substance Abuse and Mental Health Services Administration. In raw numbers, this is equivalent to almost 19 million people. Marijuana use has gone up every year since 2007, and far more people use the drug than any other type of illegal substance. Almost 80 percent of all U.S. illegal substance users smoke marijuana at least some of the time, and almost 63 percent of these users only smoke marijuana. In terms of age, the most likely users of marijuana (and most other illegal substances) are in their mid- to late-teens or in their 20s. However, significant numbers of users also appear in younger and older age ranges. Marijuana Addiction Figures from the National Institute on Drug Abuse indicate that roughly nine out of 100 marijuana users will develop an addiction to the drug. However, risks vary considerably for specific groups of individuals. The lowest risks appear in casual users who only consume marijuana on a seldom or occasional basis. Whether they consume the drug casually or habitually, teenagers have almost a 100 percent greater chance of developing diagnosable marijuana addiction. When age is not a limiting factor, the rate of addiction for all daily or near-daily marijuana consumers ranges from about one in four to one in two. Like all other substance addicts, people affected by marijuana addiction have long-term changes in their brain function that produce a chemically dependent state. The cannabis use disorder diagnosis includes these individuals, as well as people unaffected by marijuana addiction who nevertheless develop dysfunctional patterns of behavior as a result of their marijuana use. The American Psychiatric Association created this combined diagnosis in May 2013 as part of a larger modernization effort. Key Characteristics In the study slated for publication in Addictive Behaviors, researchers from the University of Vermont and Dartmouth College examined the characteristics of 142 people who used marijuana on a daily basis. All of these individuals submitted detailed information for the project over a three-month period through a phone-based survey application. Specific types of information gathered included the methods used to deliver marijuana to the body, the amount of the drug consumed on any given day, the frequency and severity of marijuana-related intoxication and the level of involvement in other forms of substance intake. On average, the study participants used marijuana roughly three times on any given day. There was not much difference between the lowest level of daily use and the highest level of daily use. The researchers also identified a number of other key characteristics in daily marijuana users, including the use of two or more methods to get \u201chigh,\u201d a tendency to smoke cigarettes and a tendency to participate in a dangerous, drunkenness-producing form of short-term alcohol intake called binge drinking. In addition, the vast majority of daily users (99 percent) reported being at least somewhat \u201chigh\u201d on the average day (with a significant number of days spent \u201cseverely\u201d high). The study\u2019s authors identified 15 variables that affect how often a daily marijuana user consumes the drug. Chief among these variable are the availability of marijuana and the user\u2019s day-to-day social environment. The authors believe they are the first group of researchers to conduct such a detailed examination of the characteristics that at least partially define habitual marijuana users. In addition, they believe that their work will increase the accuracy and usefulness of future attempts to study the defining characteristics of these addiction-susceptible individuals.