Memory and concentration impairments are often seen in chronic heavy users as well. Marijuana also contains higher concentrations of some cancer-causing chemicals. Continued abuse usually leads to dependence. Dependence occurs when someone is unable to control their use of a drug. They may not feel good or normal unless they are using and may not realize they are dependent on the drug's mind-altering effects.
Dependence is treatable and can be avoided.
First of all, know your resources. You may not initially get a positive response, but if you communicate your concerns in a supportive, non-judgmental way, you will have taken the first step. A guide to the history, uses and effects of psychoactive drugs. Wisconsin Clearinghouse, 1992. An inordinately high percentage of campus sexual assaults involve alcohol use by one or both of the persons involved.