Marijuana is widely used in the United States. In 2000, an estimated 1 in 20 (or 11 million) Americans used marijuana in any given month. This is concerning, since marijuana is associated with significant problems at school and work, increased risk of other substance use, motor vehicle crashes, and respiratory and cardiovascular disease .

While most health professionals recognize that marijuana use is rampant, no evidence has been available about changes in the prevalence of marijuana abuse or dependence in the United States.

A new study in the May 5, 2004 issue of the Journal of the American Medical Association found that while the number of Americans using marijuana remained stable over the past decade, the number diagnosed with marijuana abuse or dependence significantly increased, especially among black and Hispanic young adults.

About the Study

Researchers used data from the 1991-1992 National Longitudinal Alcohol Epidemiologic Survey (NLAES) and the 2001-2002 National Epidemiologic Survey on Alcohol and Related Conditions (NESARC). Each survey included nationally representative samples of around 43,000 adults.

During the surveys, well-trained professional interviewers obtained data about the participants’ marijuana use. In addition, they conducted a structured interview to diagnose marijuana dependence or abuse.

Marijuana dependence and abuse were diagnosed according to the criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition ( DSM-IV ). Accordingly, the diagnosis of dependence and abuse were mutually exclusive; participants could be diagnosed with one or the other—not both.

The participants who met at least three of the following six criteria were diagnosed with marijuana dependence:

  • The need for increased amounts of marijuana to achieve the desired result
  • Using marijuana in larger amounts over a longer period than intended
  • Persistent desire or unsuccessful efforts to cut down or reduce marijuana use
  • Much time spent obtaining, using, or recovering from the effects of marijuana
  • Giving up important activities in favor of using marijuana
  • Continued marijuana use despite physical or psychological problems related to use

Participants who met at least one of the following for criteria were diagnosed with marijuana abuse:

  • Recurrent marijuana use resulting in failure to fulfill major obligations
  • Recurrent marijuana use in physically hazardous situations
  • Recurrent marijuana-related legal problems
  • Continued marijuana use despite having social problems related to use

The Findings

The prevalence of marijuana use remained stable between 1991-1992 and 2001-2002, with around 4% of the participants reporting having used marijuana in the past year. While marijuana use did not increase in the sample as a whole, certain groups—black and Hispanic women ages 18-29, and men and women ages 45-64—experienced significant increases in marijuana use.

During both study periods, marijuana abuse was about three times more common than dependence. The prevalence of marijuana abuse or dependence (combined) increased significantly, from 1.2% in 1991-1992 to 1.5% in 2001-2002. This finding translates into an increase from 2.2 million to 3.0 million people diagnosed with marijuana dependence or abuse.

In 2001-2002, 35.6% of the participants who had used marijuana in the past year were diagnosed with abuse or dependence, up from 30.2% in 1991-1992. These increases were most notable in 18-29-year old black women and men, and 18-29-year old Hispanic men.

How Does This Affect You?

These findings suggest that while overall marijuana use has not increased over the past decade, more people are abusing or becoming dependent on marijuana. Interestingly, the authors of this study suggest that this increase may be related to today’s more potent marijuana. The potency of the marijuana (measured according to delta-9-tetrahydrocannabinol, or THC, levels) confiscated in police seizures increased by 66% from 1992 to 2002.

Strikingly, marijuana use and related disorders are increasing in minority young adults. A number of factors, including economics, living conditions, and even higher rates of college attendance among minorities, may have contributed to these increases. Marijuana use is also increasing among 45-64-year-old men and women, perhaps as a result of increased lifetime exposure to marijuana. (The men and women in this age group were adolescents in the late 1960s and early 1970s, when marijuana became more widely used.)

This study highlights the need for more information on the prevalence of marijuana use and associated disorders. It also brings up the need for research on other illicit drug use. These studies can help intervention campaigns target groups at highest risk for substance-related disorders . Today’s illicit drugs more potent and more accessible than ever before, so the need to quell the burgeoning problem of substance abuse is becoming increasingly urgent.