Buyer beware. Nearly 75 percent of CBD marijuana extracts sold online are mislabeled, with many of the products containing little to none of the active ingredient, according to a study led by a University of Pennsylvania researcher.

CBD, or cannabidiol, is a molecule found in cannabis believed to have therapeutic properties. Preliminary studies have found it to be effective in treating some forms of intractable seizures, pain and anxiety. It does not deliver the high associated with the better known psychoactive molecule, THC. CBD products are widely available despite a federal prohibition on their use. The DEA, and the states of Pennsylvania and New Jersey, consider CBD a Schedule 1 substance without a valid medical use.

Marcel O. Bonn-Miller, of the Perelman School of Medicine at Penn, headed a team of scientists who bought and analysed 84 mail order CBD products.

The study found 43 percent of the products had more cannabidiol and 26 percent had less cannabidiol than was noted on the label. Some of the products contained THC at levels that might cause children to become intoxicated or trigger a positive result for a drug test. The team concluded there was a need for manufacturing and testing standards if CBD products are going to be used for medicinal purposes.