There has been a lot of research into why people start using cannabis and the consequences of their doing so but much less research into why people stop using the drug, or never start using it in the first place. A study of 82,106 U.S. high-school seniors found that: 50% of those reporting cannabis use in the last year felt that they should either stop completely or cut down. Among those saying that they would not use cannabis in the coming year the most frequently reported reasons were concerns about psychological and physical damage and not wanting to get high. The least frequently reported reasons were expense, concerns about having a bad trip and availability. Girls were more likely to focus on moral and behavioural concerns about cannabis whereas boys were more likely to focus on practical concerns such as the risk of arrest, loss of energy and ambition, expense and availability. Black and Hispanic students were significantly less likely than whites to note concerns about expense, personal beliefs or getting in with the wrong crowd but were more concerned about addiction.
Terry-McElrath, Yvonne, O'Malley, Patrick M. and Johnston, Lloyd D. - Saying no to marijuana: why American youth report quitting or abstaining Journal of Studies on Alcohol and Drugs November 2008, 69(6), 796-805