[DaFace]

From a really good book on the subject:

Can marijuana use lead to dependence or addiction?

Yes, but even among frequent marijuana users only a minority suffers from a substance abuse disorder.

“Addiction” is no longer a term in medical use; the technical terms are “abuse” and “dependence,” where dependence is the more severe condition. Sometimes “addiction” is used to refer to dependence in its chronic, relapsing form.

Abuse and dependence are defined by the Diagnostic and Statistical Manual of Mental Disorders of the American Psychiatric Association, currently in its fourth edition (and thus called DSM-IV). To simplify, the DSM-IV definition of drug abuse is continued use of a substance in the face of adverse consequences. Dependence is defined as current use meeting three or more of the conditions:

1. Tolerance (needing more to get same effect)
2. Withdrawal (cessation causes a characteristic set of symptoms)
3. Using more than intended
4. Wanting to or having tried unsuccessfully to cut down on use
5. Spending considerable time obtaining and using the substance
6. Interference with important work, social, or other activities
7. Continued use despite knowledge of adverse consequences

Survey responses suggest that more than 8 million current marijuana users meet criteria 4 and 5; far fewer mention the other issues. For example, only 1.5 million report that their marijuana use is causing problems with work/school/home and with family or friends.

Taking all the criteria into account, the self-report data suggest that 2.7 million Americans met clinical criteria for marijuana dependence in 2009, and another 1.7 million met the criteria for abuse, so 4.4 million met the criteria for abuse or dependence (that’s 1.7 percent of the population aged 12 and older). Estimates from Europe and Australia also find rates of marijuana abuse and dependence in the general population between 1 percent and 2 percent. This relatively small group accounts for a considerable share of total consumption.

But regular marijuana use does not necessarily indicate dependence. Only about 30 percent of those who are estimated to have used on more than half the days in the last year self-report symptoms that suggest a diagnosis of abuse or dependence. The corresponding figure for cocaine is 88 percent. Someone who uses cocaine every other day or more often is probably cocaine dependent; someone who uses marijuana every other day or more often is probably not cannabis dependent. In this regard marijuana resembles alcohol more than it does the “hard” drugs.