Marijuana use is relatively common in the U.S., especially among older teenagers and young adults. As with other substances of abuse, a number of\u00a0underlying motivations can potentially explain initial and ongoing intake of this drug. In a study published in July 2014 in the journal Addictive Behaviors, researchers affiliated with three U.S. institutions used a screening tool called the Marijuana Motives Measure to help determine the reasons young people between the ages of 15 and 24 use marijuana on a regular basis. Among other things, these researchers concluded that the explanations provided for marijuana use can vary before and after drug intake. Marijuana and Young Users In the U.S., federal researchers regularly assess nationwide involvement in marijuana use through an annual program called the National Survey on Drug Use and Health. As of mid-2014, the latest available figures from this program cover the year 2012. In that year, roughly 18.7 percent of American adults between the ages of 18 and 25 used marijuana at least once a month. This figure represented a slight decline from the previous year, but also reflected a larger trend of growing use extending back to 2009. Roughly 14 percent of all 16- and 17-year-olds used the drug at least once a month. In 14- and 15-year-olds, the rate of use was approximately 6.1 percent. Marijuana intake is particularly damaging for younger users. For example, people who start consuming the drug before they reach their 20s have significantly increased odds of developing the symptoms of cannabis use disorder (cannabis abuse\/cannabis addiction), even if they don\u2019t smoke marijuana habitually. In addition, heavy consumption of the drug can interfere with several aspects of brain development. This is a crucial fact for young people, since the brain doesn\u2019t fully complete its final stages of development until an individual reaches his or her mid-20s. The Marijuana Motives Measure The Marijuana Motives Measure (MMM) was developed in the 1990s in order to give researchers and public health officials an improved understanding of the reasons people start using marijuana and continue using the drug over time. The screening tool lists 25 potential motivations for marijuana intake and asks the individual to describe the importance of each of these motivations. Examples of the reasons under consideration include peer pressure, a desire to feel pleasure, a desire to cope with unpleasant emotions, a desire to expand consciousness, a desire to establish social relations with others and a desire to enhance creativity. The overall score on the MMM may reflect a single primary reason for marijuana use; it may also reflect a combination of motives that have an interactive or cumulative effect on drug intake. What Motivates Young People? In the study published in Addictive Behaviors, researchers affiliated with Harvard Medical School, Boston Children\u2019s Hospital and Dartmouth College administered the Marijuana Motives Measure to 36 people between the ages of 15 and 24. All of these participants used marijuana at least twice a week. For a period of two weeks, the researchers asked each individual to fill out a computerized version of the MMM both before and after using the drug. Next, they compiled the submitted explanations and categorized them according to procedures outlined in the instructions for the screening tool. The researchers identified several key motivations for marijuana intake among the study participants, including a desire to have a pleasurable experience, a desire to deal with unpleasant feelings or circumstances, a desire to engage with others socially, a desire to expand consciousness and a desire to go along with other people\u2019s behavioral expectations. However, the researchers also concluded that the reasons given prior to the use of marijuana differed from the reasons given after marijuana use roughly 20 percent of the time. The motivations that changed most often were the use of marijuana for social- or peer-related reasons and the use of marijuana for consciousness expansion. Several factors increased the likelihood that a participant\u2019s motivation would change after marijuana intake, including using marijuana on the weekends, being male and being at the upper end of the age range under consideration. Based on their findings, the study\u2019s authors believe that many of the explanations for marijuana intake given after the fact may not be dependable or valid. This is especially true for socially oriented explanations and notions of consciousness expansion.