A 13-year-old Norwich terrier, previously limping and stiff, able to enjoy walks again. A toy poodle with epilepsy, finally relieved from seizures. In case reports, these and other dogs had their ailments eased with CBD — cannabidiol — after scant success with conventional treatments.
Evidence is growing that CBD, a non-psychoactive ingredient of cannabis, is potentially effective in treating various pet maladies, from pain and itching to seizures, says Chie Mogi, lead veterinarian of the Animal CBD Research Society in Japan, who has reported such cases in veterinary publications.
The positive reports also extend to more rigorous trials with placebos. “This was exciting to me because, quite honestly, I was worried that, despite the hype, it wouldn’t show a difference when studied more objectively,” says veterinary neurologist Stephanie McGrath of Colorado State University, coauthor of a review of CBD for dogs and cats in the 2023 Annual Review of Animal Biosciences.
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Though the evidence for effectiveness is still mixed, and pet owners and researchers must contend with inconsistent ingredients, many scientists have hope that CBD can expand the therapeutic options for furry patients.
The CBD boom follows relaxed cannabis regulations over the past decade that opened the door both for the cannabis industry and research. In 2018, the US Farm Bill legalized hemp containing 0.3 percent or less THC (tetrahydrocannabinol, the cannabinoid mainly responsible for marijuana’s high). Companies could now sell products consistent with that guideline, including supplements containing CBD. Since then, hemp pet products have proliferated, and the global market is expected to hit $3.05 billion by 2025.
Although CBD does not create a high, it does interact with numerous receptors in the brain, providing a rationale for therapeutic effects. Plus, CBD is processed more slowly in dogs and cats than in people, making any effects last longer, says Cornell University veterinarian Joseph Wakshlag, who also serves as the chief medical officer for ElleVet Sciences, a pet CBD company. Surveys suggest many owners have tried treating pets with CBD, mostly for issues related to pain, sleep, anxiety and seizures.
Only recently have a few states passed laws explicitly allowing veterinarians to recommend CBD products, leaving prescription of hemp products a gray legal area in other parts of the country. And many vets remain skeptical. Recently, though, research has shown benefits for specific conditions.
Two 12-week clinical trials, totaling 30 dogs, reported that CBD eased symptoms of epilepsy, picking up the slack in cases where other drugs haven’t adequately helped. In both trials, dogs that were already taking anti-seizure medication were dosed twice daily with CBD — one study with 2 milligrams per kilogram of body weight, the other 2.5 milligrams. Compared with placebo treatments in which dogs received only the regular medicine, CBD-dosed dogs, on average, experienced about 30 percent fewer seizures over the course of the trial.
Some dogs and cats are very itchy, seemingly allergic to the world, and sometimes even veterinary diets and medications don’t make much impact. In one 2021 study, 24 kenneled shelter dogs were dosed with up to 4.5 milligrams (per kilogram of body weight) of CBD daily for three weeks. The canines wore activity monitors on their collars that logged how long they spent walking, running, shaking their head, scratching and resting. The study reported that dogs given CBD scratched up to 50 percent less, though some of the results did not reach statistical significance.
Another report documented reduced skin redness and hair loss in eight dogs with atopic dermatitis, or chronic skin irritation. Cannabinoids may be able to protect against inflammatory responses in the skin — and thus itchiness, other research has suggested.
Some studies have reported a benefit in arthritic dogs, though the results are mixed. In one paper, 16 dogs with osteoarthritis were given CBD oil twice a day for four weeks. At two weeks and four weeks, owners responded to surveys about their dog’s pain and activity levels. Compared with a placebo treatment, owners reported greater decreases in their pets’ pain, alongside increases in activity, while taking CBD. In one measurement, a subjective rating scale with a maximum score of 40, pain ratings went down from an average of 21 to an average of 14. “Dogs that jump in the car again … they climb the stairs, they jump on the bed — all these things are what the owners notice,” says Wakshlag, a coauthor on the paper.
But another pain study reported no improvement in arthritis in 23 CBD-dosed dogs. In this report, the researchers relied on veterinary assessments of mobility, which included having the dogs walk on a treadmill-like device that measured the force of their paws — making it possible to detect subtle differences in gait, such as reduced limping.
Testing CBD’s effectiveness in calming pets has also produced mixed results. In a 2020 study during which 16 dogs listened to an audio track of fireworks, CBD showed no effect on signs of stress such as blood cortisol levels and tail-tucking. But in a more recent study, dogs taking CBD showed fewer stress signs on car trips, including lowered cortisol and less frequent lip-licking and whining.
Conflicting results don’t necessarily mean that CBD is ineffective. For one thing, every measurement method and protocol has limitations, says Pernille Holst, a veterinary oncologist at the University of Copenhagen. Doses used in studies also vary widely — in the car-trip study, for example, dogs received doses nearly three times higher than did dogs in the firework-noise study.
Even the chemistry of the hemp product used may make a difference, says Wakshlag. Full-spectrum hemp extracts that contain cannabinoids in acid forms may act differently than do CBD isolates.
More research could clear up these questions and also help fill in the CBD picture for cats, for which research is especially scarce. But large-scale clinical trials are not cheap, and pet CBD companies don’t have the same resources as human pharmaceutical companies, says animal science researcher David Harmon of the University of Kentucky, who coauthored the firework-noise study. “There’s no conglomerate with large capital to accomplish these things,” he says.
Further complicating matters for owners is the fact that pet cannabis companies have little oversight and sometimes produce questionable products. In one study of 29 hemp products, more than half were outside the advertised range of CBD by 10 percent or more. In four products, researchers detected heavy-metal contamination. “I wish there was more oversight and regulation to ensure the labels match the product, but currently there is not,” says McGrath.
A good bet for pet owners is to buy from companies that participate in voluntary programs such as the National Animal Supplement Council, Wakshlag says.
Kris Paige, a retired veterinary technician, enrolled her dog Purdy in a Colorado State University clinical trial for CBD treatment after the Anatolian shepherd began having grand mal seizures about every three weeks. Over the six-month trial, Paige observed Purdy’s seizure frequency go down — albeit not as much as she’d hoped — to an average of one every four weeks. These days, she no longer gives Purdy hemp oil daily but only after a seizure, which appears to lessen the dog’s confusion and anxiety.
Paige is glad Purdy participated in the research. “While the results weren’t what we were hoping for,” she says, “it added to the knowledge.”
This article originally appeared in Knowable Magazine, an independent journalistic endeavor from Annual Reviews. Sign up for the newsletter.