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Heavy, Long-Term Use of Cannabis Might Be Linked to Numerous Negative Features in American Users

Long-term heavy cannabis use is associated with several negative features on both objective measures and self-ratings of health and life satisfaction, according to researchers from McLean Hospital, Belmont, Massachusetts, United States.

Despite multiple previous studies of heavy cannabis users, little recent information has been gathered to compare attributes of long-term, frequent users with non-users or light users in the United States.

To provide more current data, Amanda J. Gruber, MD, and colleagues compared the attributes of 180 individuals, age 30 to 55 years, who were grouped on the basis of their history of cannabis use.

Based on telephone screening, the researchers identified 63 current long-term heavy users (who reporting lifetime cannabis use of 5000 or more times and current use of 7 or more times per week), 45 former long-term heavy users (reporting lifetime cannabis use of 5000 or more times and current use of up to 1 time per week), and 72 controls (reporting lifetime cannabis use between 1 and 50 times).

Enrolled subjects entered a 28-day period of supervised abstinence from cannabis, and received evaluations including administration of the Structured Clinical Interview for Diagnostic and Statistical Manual - Revision IV (SCID), the Wender Utah Rating Scale (WURS), and the Attention Deficit Hyperactivity Disorder (ADHD) rating scale.

Results showed that in virtually all cases there was no statistically significant difference between current and former long-term heavy users. Likewise, no significant differences were observed between heavy users (former and current user groups combined) and controls regarding reported levels of income and education in their families of origin.

However, despite the similarities observed in familial income and education, heavy users reported significantly lower educational attainment (P < .001) and income (P = .003) than controls.

Additionally, the majority of heavy users (66-90%) reported a "negative effect" in rating the subjective effects of cannabis on cognition, memory, career, social life, physical and mental health and quality of life.

The researchers note that whether the findings would generalise to other cultures - where patterns of cannabis use and associated behaviours may be very different - is not clear.

"Further studies are needed to better understand the direction of causality in these associations, since this information will be important for developing better strategies to treat cannabis dependence," they conclude.
Psychol Med. 2003 Nov;33:8:1415-1422. "Attributes of long-term heavy cannabis users: a case-control study"

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