Category: Forensic Toxicology
An Increase in Pre-Employment Cannabis Positivity Is Not an Increase in Measured Impairment
A clinic’s rising cannabis urine positivity rate measures a change in detected exposure, not a measured rise in workplace impairment. A California retrospective study also demonstrates why absolute and relative changes must be reported together. Which result counted as positive? Sharip and Razavi reviewed 21,546 pre-employment screenings from one occupational…
When Teen Drivers’ Cannabis Reports and Biological Tests Disagree
A disagreement between self-reported cannabis use and a THC test is not automatically proof that either measure is useless. A national roadside study illustrates how reporting windows, specimen differences, and study participation affect interpretation. What was compared? Pressley and colleagues examined drivers aged 16–19 in the 2013–2014 National Roadside Survey….
Why Low Oral-Fluid THC Does Not Rule Out Other Drug Exposure
A low oral-fluid THC concentration does not establish that cannabis was the only substance present. Spanish roadside data found other drugs frequently detected alongside THC, including among samples with relatively low THC values. The denominator changes the meaning Herrera-Gómez and colleagues analyzed administrative roadside testing data from 2011–2016. Among 65,244…
Can Exercise or a Day of Fasting Explain a Rising Cannabis Urine Result?
A small inpatient study did not find large cannabinoid increases after moderate exercise or a day without food. It offers limited evidence against routinely attributing a rising urine result to those activities, while leaving more extreme conditions untested. The intervention and specimens Westin and colleagues studied six chronic daily cannabis…
Kidney Disease and Cannabinoid Testing: Why Lower Urinary Excretion Can Accompany Higher Exposure
Patients with advanced chronic kidney disease can show greater cannabinoid exposure while excreting less of certain metabolites in urine. A clinical pharmacokinetic study demonstrates why urine results should not be treated as a direct gauge of circulating exposure. What was compared? Sønderskov and colleagues compared people with advanced kidney disease…
Can Portable Brain Imaging Measure THC Intoxication? What Prefrontal Connectivity Shows
Oral THC altered prefrontal brain signals in a controlled human experiment, but those changes do not yet establish a universal roadside impairment test. The distinction is between a reproducible research association and a validated individual decision rule. What did the instrument record? Karunakaran and colleagues used functional near-infrared spectroscopy, an…
Cannabis and Response Inhibition in People at Clinical High Risk for Psychosis
A small controlled study found adverse cognitive responses to smoked cannabis in participants at clinical high risk for psychosis. It raises a susceptibility question without establishing a diagnostic test or proving that all people with that risk respond alike. A carefully selected, very small sample Madden and colleagues studied six…
Medical Cannabis and Lane Control: What an Open-Label Simulator Study Can Establish
A study of established medical cannabis patients found little deterioration in simulated driving after their prescribed dose. Its open-label design and testing schedule limit what that finding says about early effects, new patients, or an individual driver. Who was tested, and when? Manning and colleagues studied 40 adults who consumed…
Does THC-Related DNA Damage in Rats Establish Human Cancer Risk? Reading the Comet Assay
A rat experiment found low-level DNA damage after high-dose THC exposure, but it did not establish that THC causes cancer in humans. The meaning of the finding depends on the assay, tissue, exposure regimen, and outcomes that were actually measured. What was tested? Kopjar and colleagues administered THC orally to…
A Highly Linear THC Biosensor Is Not Yet Proof of Accurate Testing in Every Urine Sample
A strong calibration curve is useful evidence about a sensor, but it does not establish its diagnostic accuracy in an unselected population. A flexural plate-wave THC microsystem demonstrates the difference between engineering performance and the evidence needed for routine forensic use. What did the device measure? Lan and colleagues built…
Can Oral THC Data From Monkeys Predict When an Edible Peaks in Humans?
A vervet-monkey study observed oral THC concentration peaks around four hours, but that is not a universal timetable for human edibles. The experiment helps characterize an animal model while also showing why repeated exposure and the particular analyte matter. What was measured? Huppé-Gourgues and colleagues administered THC orally to vervet…
When a Negative Cannabis Urine Screen Needs a Specimen-Validity Review
A negative cannabis immunoassay can reflect analytical interference rather than absence of the target metabolite. A laboratory study of benzalkonium chloride illustrates that vulnerability and a way to investigate it. It does not justify assuming that every negative sample was deliberately altered. What chemical was the test trying to detect?…
