Treatment with CBD

Treatment with CBD – Your Gateway to the Science of Cannabidiol

Is THC contamination the true cause of CBD side effects?

Since both the United States and the European Union have reapproved the cultivation of low-THC hemp varieties, we have seen rapid growth in various parts of the hemp plant being used in the production of foods, other edibles, and liquids used in vaping – hence the urgency to know about the potential contamination of CBD with THC.

Cannabidiol (CBD) is attracting lots of interest for its numerous potential health benefits. Inevitably, this has boosted the availability of large numbers of new foods and liquid products, claiming to contain cannabidiol and promising often unverified and unproven health benefits. These products are widely available in various health shops, drugstores, supermarkets, and the internet.

Taking CBD products can be a safe alternative to (medical) marijuana, without the added effects of THC. Unfortunately, however, the regulation of the CBD market is poor, and therefore there is a large variety in adherence to label claims due to unstrict manufacturing and handling protocols, procedures, and processes.

Hemp seed vs CBD products

The production of commercial (non-medicinal) cannabidiol products is generally relatively crude. The source of extracts is typically the whole hemp plants, including stems, flowers, and seeds, which produces only a low CBD content, often well-below the claimed content of between 1–10%. Producers may do some further “cleaning” , but to reduce production costs, manufacturers may simply use solvents to extract CBD from the entire plant, with no additional purification or enhancement, producing a mixture of cannabinoids rather than pure CBD. 

These full-spectrum cannabis extracts are then mixed with edible oils to create what is commonly referred to as “CBD oil”. Cannabidiol is available on the market as capsules or liquids or added to other products.

While hemp seed products without cannabinoids are generally regarded as safe (GRAS), they can be marketed in the EU. However, cannabidiol is relatively new on the market in Europe, it is classified as Novel Food, and is not officially authorized to be marketed according to EU law.

Given the unclear legal and regulatory status of CBD, many questions arise regarding CBD product safety. One of these is that CBD might convert under certain circumstances into the psychotropic THC. As such, the main question is whether the potential CBD side effects are in actuality due to THC contamination.

Side Effects of CBD products

Following complaints of side-effects from using these CBD products, regulatory authorities and researchers have investigated them further. A US survey of 135 CBD users described side effects such as dry mouth, feeling high, appetite changes, tiredness, and drowsiness. The suspicion was that these effects might be explained by the pharmacological properties of THC and not CBD, and could be due to previously unknown pharmacological CBD effects, the breakdown of CBD into THC in the stomach, or the presence of THC in the product itself

What are the causes of CBD side effects?

Research suggests that pure CBD is unlikely to produce THC like side-effects, especially at the very low doses found in commercial products. Therefore, researchers tested a large range of commercial CBD products to see if they degraded into THC under different storage conditions and in simulated gastric juices. However, they found no THC present after each test.

As a result, researchers concluded the side effects could be best explained by the presence of THC as a contaminant, through an incomplete or poorly carried out purification manufacturing process – something the European Industrial Hemp Association has disputed.

Nevertheless, these findings have additional support from the testing of commercial hemp and CBD products in Germany and the US, respectively. A German analysis found that the contents often varied dramatically from the label information, with a quarter (17 out of 67) products containing THC levels that were “harmful to health” and 29 classified as “unsuitable for human consumption”.

In the US testing, the label showing CBD content was correct in just 26 of 84 products, and 18 products had unlisted THC greater than 0.317g/100g. Most worryingly, several products had no labeling about content at all. Typically, a THC dose of 10-20 mg can lead to intoxication, although individual tolerance varies greatly so that one in five people show significant symptoms with just 5 mg.

Are the CBD side effects really due THC contamination of CBD?

Unsurprisingly, the European Industrial Hemp Association (EIHA), representing the interests of the Hemp industry, disputes these claims. The EIHA stated that the research did not show that it was the presence of THC that caused the side effects. They noted that the findings did not clearly discuss tetrahydrocannabinolic acid (THCA), a non-psychotropic precursor of THC.

In addition, no proof of side effects were presented. If the side-effects were, in fact, genuine, then whatever the cause, the unregulated products were causing their users unwanted ill-effects and were in some cases, either wilfully or incompetently, mis-labeled.

What does the future hold?

The research notes that CBD degradation products are still unknown, and without this, it is not possible to say if the side effects are due to CBD itself or degradation or contamination. The unregulated market and production of these products makes the situation even more complex, with no standardized process for purification and storage, for example.

It is important, however, that manufacturers that are deliberately misleading consumers and ignoring the legal situation must be challenged. In a telling quote from Pal Pacher, president of the International Cannabinoid Research Society, he stated that CBD users should be fully aware that they were “participating in one of the largest uncontrolled clinical trials in history”. 

Perhaps an unanticipated risk might also include users testing positive for cannabis in occupational or sports-related testing, for example, as a quarter of products tested had sufficient THC to cause a false-positive result. 

It is clear that the current legal framework is inadequate to regulate cannabis-derived products like CBD, which fall between being categorized as a foodstuff, illegal narcotic, or prescription-based medicine. It would seem appropriate that governments recognize CBD products alongside other medicinal cannabis products or as dietary supplements, so that stricter manufacturing regulation and accurate and honest labeling are mandatory, along with standard safety testing and approval.


Lachenmeier DW, Habel S, Fischer B, et al. Are side effects of cannabidiol (CBD) products caused by tetrahydrocannabinol (THC) contamination? [version 3; peer review: 2 approved, 1 approved with reservations] F1000Research. 2020, 8:1394.

Kruse D, Beitzke B. Comment on Lachenmeier et al (2020) “Are side effects of cannabidiol (CBD) products caused by tetrahydrocannabinol (THC) contamination?”: disputation on various points in the publication. F1000Res. 2020, 9:900. Published 2020 Aug 4. doi:10.12688/f1000research.25354.1