And did cannabidiol really kill four-and-a-half mice? BY ADRIAN DEVITT-LEE ON JULY 11, 2019 (UPDATED 18th February 2020)

A small rat perches on top of a bouqet of daisies on a wooden table.

The huge popularity of cannabidiol (CBD), a non-intoxicating component of cannabis, has helped to destigmatize the plant and restore its reputation as an important medicinal herb. But bogus science and inept reporting continue to distort how we understand the benefits and risks of CBDand cannabis.

An article by Mike Adams in Forbes online rang alarm bells by asserting that CBD“could be damaging our livers in the same way as alcohol and other drugs.” This sensational claim was based on a dubious study of CBD and liver toxicity conducted by researchers (Ewing et al) at the University of Arkansas in Little Rock – except the damage discussed in the study was unrelated to alcohol toxicity and “our livers” actually refers to mouse livers.

The Little Rock study made no mention of humans, which is a hugely important distinction. Moreover, in the real world CBD consumers are not ingesting 0.25% of their body weight – the maximal dose that Ewing et al used in their study of liver toxicity.1

Nevertheless, according to Forbes, “People that use CBD are at an elevated risk for liver toxicity.” And “[CBD] may actually be just as harmful to their livers” as “conventional pain relievers, like acetaminophen.” These statements are clearly unsupported by the current literature.

Related story: What is CBD?


The breathless reporting in Forbes focuses on a single, flawed, preclinical study and exaggerates it to the point of falsehood. Yet if there’s a saving grace of the Forbesarticle, it’s that it gets much less wrong than the study itself. The study is freely available from Molecules, a journal published by the Multidisciplinary Digital Publishing Institute (MDPI).

A close examination of the Molecules study reveals a Pandora’s box of strange statements, problematic publishing and unreasonable experimental design. On the first page, the abstract makes a claim that is fundamentally impossible, stating that, with chronic administration of CBD, “75% of mice gavaged with 615 mg/kg developed a moribund condition.” But there were only 6 animals that received this dose! One doesn’t need an advanced degree in science or math to recognize that something is amiss. Seventy-five percent of six equals 4.5.

According to the Little Rock researchers, four-and-a-half mice died because of the dangerous drug known as CBD, while somehow one-and-half mice survived.

Reading on, it only gets worse.

The experimental set-up is succinct. Scientists force-fed mice a single dose of CBD, ranging from the supposedly “low” dosage of 246 mg/kg up to a mega-dose of 2460 mg/kg CBD. That means for every kilogram of body weight, they gave the mice about 2.5 grams of CBD, which had been formulated as a hexane extract2 from cannabis supplied by the National Institute on Drug Abuse (NIDA). Hexane, it bears mentioning, is a neurotoxin.

“According to the Little Rock researchers, four-and-a-half mice died because of the dangerous drug known as CBD.”

The maximum human dosage recommended for the CBD-isolateEpidiolex is 20 mg/kg, which is over 100x less than what the Little Rock researchers force fed their experimental mice. They also tried smaller doses (ranging between 61.5 to 615 mg/kg) of CBD, which was given daily for 10 consecutive days.

Despite these ridiculous dosages, Ewing et al.3 claim their study accurately represents human experience, insisting that the equivalent human dose is 12.3 times lower because of allometric scaling (which we will discuss momentarily). This is – at best – an unverified assumption. More likely, it’s just plain wrong.


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