Can a Urine Cannabinoid Result Measure Cannabis Withdrawal Severity?
Serial urine cannabinoid results showed a limited association with withdrawal symptoms in a selected inpatient population, but they did not provide a stand-alone measure of an individual’s symptoms or impairment. A positive urine result, a withdrawal assessment, and a determination of intoxication answer different questions.
Claus and colleagues investigated 78 adults undergoing inpatient cannabis detoxification in Germany, with observations over as long as 24 days. The original human study is published in Frontiers in Psychiatry, doi:10.3389/fpsyt.2020.598150.
What the urine test actually measured
The investigators used a commercial semiquantitative immunoassay calibrated with THC-COOH, the carboxy metabolite of THC. Although the paper describes its readings as THC-COOH levels, the authors explain that the assay can respond to other cannabinoids. Its reported concentration is therefore not identical to a compound-specific mass-spectrometric measurement of that metabolite alone.
The matrix was urine. The assay was not measuring a driver’s whole-blood parent THC, brain concentration, or performance behind the wheel. THC-COOH is a nonpsychoactive metabolite; detecting it does not establish that the person is currently intoxicated.
How strong was the association?
Across serial observations, the unadjusted urine measurements correlated with Marijuana Withdrawal Checklist scores at r=0.248, with P<.001. That is a statistically significant but limited relationship. A low P value does not make the association sufficiently precise to predict one person’s symptom burden from one specimen.
After correction for urine creatinine, the corresponding repeated-measures correlation in the overall sample was not statistically significant: r=0.096, P=.059. In participants with higher symptom scores at admission, however, the creatinine-normalized measurements did correlate significantly with symptoms. Analyses accounting for other variables also affected the results. These findings should be identified by analysis and population rather than compressed into a claim that every urine value predicts withdrawal.
Why dilution and serial observations matter
A urine concentration can vary with the concentration of the specimen itself. Creatinine normalization attempts to address that problem, while introducing its own assumptions and sources of variability. The difference between the adjusted and unadjusted results is a reason to inspect the underlying measurements.
The research relied on repeated specimens and repeated clinical assessments. Hundreds of observations do not represent hundreds of independent patients. An isolated screening result from a workplace, custody dispute, or traffic investigation does not reproduce this monitored inpatient design.
What prolonged positivity meant in this setting
The investigators observed a subgroup with prolonged withdrawal and persistent urine cannabinoid readings. Females had a slower decline in urine readings in the study’s models. Those are population observations in treatment-seeking patients, not sex-specific deadlines for a negative test or proof of undisclosed consumption.
The study used procedures to identify possible relapse, but neither its screening cutoff nor a single positive urine result supplies a universal last-use clock. Related distinctions are discussed in our article on why urine and blood drug results are not interchangeable.
Limits on applying the research to a case
Participants were selected for cannabis dependence and inpatient treatment. Concurrent tobacco use, symptom medication, self-reported last use, and loss of observations as patients improved complicate interpretation. The authors also acknowledge immunoassay specificity limits and restricted generalizability.
An expert relying on this paper should identify the actual assay, specimen concentration and creatinine, sampling sequence, clinical symptom ratings, and differences between the patient and the study population. The research supports studying urine trends alongside clinical assessment. It does not validate replacing that assessment with a number.
Primary research
Claus BB, Specka M, McAnally H, Scherbaum N, Schifano F, Bonnet U. Is the Urine Cannabinoid Level Measured via a Commercial Point-of-Care Semiquantitative Immunoassay a Cannabis Withdrawal Syndrome Severity Predictor? Front Psychiatry. 2020;11:598150. https://doi.org/10.3389/fpsyt.2020.598150.
