Cannabis Study House - NORML Weekly News in Audio 2006.2.23

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Weekly News in Audio

February 23, 2006

Marijuana Detection Time Shorter Than Previously Assumed

Maternal Marijuana Use Not Associated With Childhood Leukemia, Study Says

Columbia, MO, USA:
Marijuana Detection Time Shorter Than Previously Assumed

The length of time cannabis metabolites may be detected, on average, on a standard urine screen is typically no longer than ten days for chronic users and between 3-4 days for infrequent users, according to a literature review published in the current issue of the journal Drug Court Review.

"Recent scientific literature indicates that it is uncommon for occasional marijuana smokers to test positive for cannabinoid [metabolites] in urine for longer than seven days" at 20 ng/ml or above on the EMIT (Enzyme Multiplied Immunoassay Technique) test, the author concludes. "Following smoking cessation, chronic smokers would not be expected to remain positive for longer than 21 days, even when using the 20 ng/ml cannabinoid cutoff."

When tested at the 50 ng/ml cutoff threshold, infrequent users typically test negative for the presence of marijuana metabolites within 3-4 days, while heavy users typically test negative by ten days after ceasing use, the study found.

While several clinical trials from the 1980's found cannabis metabolites to be identifiable in the urine at low concentrations for longer periods of time, particularly in heavy users, the author suggests that more advanced drug-testing technology has narrowed this window of detection.

"As cannabinoid screening tests evolved, these improved assays became more selective in the manner in which they detected marijuana metabolites," the author writes. "As detection specificity increased, the length of time cannabinoids were being detected in urine decreased. ... Therefore, the results of cannabinoid elimination investigations performed in the 1980's may no longer be applicable to estimating the detection window for marijuana in urine using today's testing methodologies."

After reviewing data from more recent clinical investigations of chronic marijuana smokers, the author reports that the "average detection window for cannabinoids in urine at the lowest cutoff concentration of 20 ng/ml was just 14 days." However, the author also notes that a minority of subjects continue to test positive for cannabis metabolites after 28 days, even when tested by more advanced drug-testing technology.

Approximately 55 million drug screens are performed annually in the United States. The majority of these are workplace urinalysis tests, which detect the presence of drug metabolites (inert byproducts produced after a substance is metabolized by the body), but not the substance itself. Consequently, the US Department of Justice affirms that a positive drug test result for the presence of a drug metabolite "does not indicate ... recency, frequency, or amount of use; or impairment."

Chapel Hill, NC, USA:
Maternal Marijuana Use Not Associated With Childhood Leukemia, Study Says

Marijuana use by mothers is not associated with an increased risk of childhood acute myeloid leukemia (AML) in offspring, according to a case-control study to be published in the March issue of the journal Pediatric and Perinatal Epidemiology.

Researchers at the University of North Carolina at Chapel Hill analyzed 517 cases of children with AML and 610 unmatched controls. Incident cases were defined as children less than 18 years of age who had been diagnosed with AML between 1989 and 1993, and were registered with the Children's Cancer Group (a pediatric clinical co-operative group). Control children were selected via random digit dialing and individually matched.

"Overall, no positive associations between parental marijuana use and childhood AML were observed," investigators found. In addition, researchers found that self-reported maternal marijuana use "in the 3 months before, or during pregnancy was associated with a decreased [risk] of childhood AML."

They added: "Some evidence of a dose-response relationship was observed with those reporting use once or more per week in the 3 months before pregnancy having a more reduced odds ratio than those reporting less than once per week. Decreased odds ratios were also noted for maternal marijuana smoking in the year after birth."

Investigators did not conclude, however, that maternal marijuana use could protect against AML. Rather, they suggested that the inverse association may be the result of "recall bias" (e.g., case mothers may have been less likely than control mothers to report having used marijuana before or during pregnancy).

The study's results contradict the findings of a 1999 investigation that did note an association between maternal cannabis use and childhood AML.

"The previously reported positive association between maternal marijuana use before or during pregnancy and childhood AML was not confirmed in this study," investigators concluded. "Parental marijuana use is unlikely as a strong risk factor for childhood AML."

The UNC study is the largest epidemiological study of childhood AML to date in the United States.

Acute myeloid leukemia comprises approximately 16 percent of leukemias diagnosed in individuals younger than 15 years of age.