Introduction

My first experience with CBD oil as a physical therapist came from one of my patients. She was an 85-year-old woman who had back pain for decades. Nothing really helped her, including multiple courses of physical therapy, medications, injections, and other products. She tried just about everything. Then one day she came in with excitement.

She had mentioned that her doctor approved her for medical cannabis and gave her a card that allowed her to go to the only dispensary on Long Island to get marijuana-related products. She came back with massage cream with Cannabidiol, or CBD, in it. She wanted me to use it in place of the typical massage cream I use for soft tissue mobilization. Remarkably, after a few weeks of CBD oil massages, she reported that her back was in fact feeling better.

With the softening of marijuana laws around the country, CBD products are entering into the spotlight and allegedly have significant health benefits. These proposed benefits include help with chronic pain, epilepsy, depression, anxiety, inflammation, weight loss, and even cancer. So what does the science really say?

What is CBD Oil?

The relationship between hemp, marijuana, and their related products may be a bit confusing. First, they all come from the cannabis sativa plant. Different varieties of this plant, cultivated in specific ways, can have different chemical components, termed cannabinoids.

One cannabinoid is cannabidiol, or CBD, which can be extracted and put in oil form and has no psychoactive properties. Another is tetrahydrocannabinol, or THC, and that is responsible for the high people get when they use marijuana. Hemp plants have a high concentration of CBD and a low concentration of THC and thus do not get you high. Marijuana plants have the opposite concentrations (30).

Both plants have different medical, recreational, and other uses. Both compounds have generated significant medical interest, but this article will focus specifically on CBD.

Is There Any Research?

With growing popularity, the research on CBD oil and other cannabis-based products is emerging. Much of the research now is preclinical, meaning the experiments are performed in laboratory conditions on cells or animals, but some small-scale clinical trials on humans have been performed. A preliminary search on PubMed, a website that indexes scientific research, reveals about 2,000 matches. A similar search for medical marijuana reveals about 4,000 matches.

Does CBD Oil Calm Childhood Epilepsy?

Cannabis-based products have long been said to be effective for helping to reduce and control seizures in children. A few recent studies have shown that CBD oil does in fact help to do this. Three placebo-controlled studies on patients with Dravet Syndrome or Lennox-Gastaut syndrome, both associated with severe seizures, were recently completed in 2017 and 2018.

Each study had similar results; a daily cannabidiol solution, in addition to their normal medication, was able to significantly reduce seizure frequency over a period of 14 weeks compared to a placebo (6, 7, 26). Each study reported significant side effects, including diarrhea, fatigue, fever, sleepiness, vomiting, and changes in appetite.

A 2018 review of 35 randomized controlled trials (including the ones above) and observational trials found that the evidence to date shows that cannabinoid-based products can result in reduced seizure frequency. However, there are relatively few placebo-controlled trials, and these trials show significant side effects. We need more research for patients with other groups of diseases (25).

Bottom Line

There is strong evidence CBD oil can help reduce and control seizures in some children, but there are side effects and we need more research for other types of epilepsy.

Does CBD Oil Provide Relief from Chronic Pain?

chronic painAnecdotally, many report cannabis-based medications can relieve pain of all types. Much of the research thus far has focused on specific populations such as patients with cancer-related pain, multiple sclerosis, or other conditions involving neurological pain. In addition, CBD has mainly been tested in combination with THC in the form of oromucosal spray.

One thorough review of cannabis-based medications for neuropathic pain relief found that the majority of the research focused on the THC/CBD mixture. While the placebo-controlled trials available showed some small benefits, the overall quality of the research was very low, and the side effects reported may not outweigh the benefits (18).

Two placebo-controlled trials for THC/CBD spray found that compared to a placebo, there were no additional pain-relieving benefits for patients’ cancer-related pain (8, 13). However, two similarly-designed trials found there were improvements as compared to a placebo for patients with neuropathic pain and cancer-related pain (10, 22). One study from 2006 compared THC/CBD spray to a placebo for patients with rheumatoid arthritis and found there were small improvements in pain over the placebo group (3).

I was unable to find any human studies that focused on CBD oil specifically, or any studies that looked at typical aches and pains associated with musculoskeletal injuries or surgeries. As the author of one narrative review put it, “it has to be concluded that rigorous clinical evidence is really not available supporting this claim at this point in time” (17).

Bottom Line

We have no strong evidence that shows CBD is helpful for pain relief despite some studies showing positive outcomes. Much of the current research on THC/CBD spray shows mixed results. We need more placebo-controlled trials on different populations with different conditions to get a better sense of what it can do.

Does CBD Oil Reduce Anxiety and Depression?

Due to many reports of people self-medicating themselves with cannabis-based products, some scientific research has been performed on the effects of CBD oil on anxiety and depression. Much of the preclinical research on animals and some non-experimental human research suggests there are some beneficial effects for various mental conditions (4, 11, 24). But what does the experimental research say?

One small study was performed in 2011 on 24 people with generalized social anxiety disorder (SAD) and 12 healthy control subjects. Half of the subjects with SAD were given a CBD solution, while the other half were given an identical placebo solution. The results showed the experimental group had significantly lower self-reported anxiety and discomfort during a simulated public speaking task as compared to placebo controls (1).

A similar study was performed in 2017. Researchers divided a group of sixty healthy people into five groups; three had various doses of CBD, one group had a placebo, and one group had a Clonazepam, a commonly prescribed anxiety medication. They made each subject perform a public speaking task and measured their anxiety levels, among other things. They found that a moderate dose of CBD was best able to reduce anxiety, compared to a low dose or a high dose during the test (29).

The effects of CBD oil on depression has not been studied as extensively. A systematic literature review from 2017 was unable to find any clinical trials assessing the effectiveness of CBD as an antidepressant, and the literature is limited to preclinical science so far (12).

According to the authors, the current body of research on CBD oil for psychiatric conditions is promising, but we don’t have any experiments we can be confident in for the majority of the conditions CBD oil is proposed to treat (12).

Bottom Line

There is promising preclinical research on CBD oil and a few trials that show it may reduce anxiety, but we do not have enough strong research to be confident it can treat other psychiatric disorders.

Does CBD Oil Fight Multi-Drug Resistant Bacteria?

Many purveyors of CBD oil and related products claim it can help fight against bacteria and can be used like an antibiotic medication. I was unable to find any studies with an appropriate design to test this claim in humans. These claims are based on preclinical research or animal studies, which while interesting, are not adequate to appropriately address whether CBD oil can fight bacteria.

Bottom Line

There are no human trials on CBD oil assessing if it can fight bacteria.

Does CBD Oil Reduce Oxidative Stress And Inflammation?

Both inflammation and oxidative stress (the imbalance between free radicals and our body’s ability to remove them) have been implicated in many disease processes, and thus much clinical interest has gone into medications that can help treat it. CBD oil has been said to be beneficial to help with these two things and some preclinical research has been performed looking at this relationship.

According to one review, cannabidiol has been shown in animal models to suppress the inflammatory response of various diseases such as multiple sclerosis, rheumatoid arthritis, colitis, and hepatitis (19). However, I was unable to find any high-quality human trials assessing these claims.

Bottom Line

The research on the anti-inflammatory effects of CBD oil is in its infancy and is restricted to preclinical research. We don’t know if CBD oil is effective in humans for achieving these goals.

Does CBD Oil Promote Healthy Weight?

CBD oil has also been proposed by many as a weight-loss treatment and has been said to help regulate metabolism. Unfortunately, I was unable to find any clinical studies on humans investigating the effects of CBD oil on weight. There are some cell studies and animal studies, but these are exploratory studies that cannot tell us if CBD oil is effective in real-world scenarios.

Bottom Line

There are no studies that show CBD oil can help with promoting a healthy weight, and any claim to the contrary is not based on science.

Does CBD Oil Fight Cancer?

Like with many supposed cure-all treatments, it has been suggested by some that CBD oil can help fight cancer. As usual, these claims seem to be exaggerated when looking at the available evidence. The current body of evidence is extremely small, and limited to preclinical and non-human research. I was unable to find any trials in humans showing CBD oil was able to fight cancer. A few interesting studies on cell cultures and mice suggest CBD oil has some effects on tumors (14, 15, 16, 23). However, these studies are not designed to show CBD oil is effective to treat cancer; they are only designed to explore its potential.

More often, CBD oil has been studied as an adjunct to help patients deal with the associated symptoms of cancer, including pain, nausea, and vomiting, but the research on this is not strong either (5).

Bottom Line

Despite compelling preclinical research, there is no strong evidence that shows CBD oil can help fight cancer. Any claim to the contrary is premature at best, or a lie at worst.

Does CBD Oil Treat Skin Conditions?

The potential benefits of CBD oil on skin conditions have begun to be explored. A 2014 study on human skin cells found that cannabidiol can disrupt cellular pathways that can lead to acne (20). Another study from 2013 found cannabidiol can affect cell proliferation and specialization in skin cells, which led the authors to conclude it may play a role in new therapeutic drugs for skin conditions (21).

One study from 2007 found that cannabidiol can inhibit the proliferation of keratinocytes, which are skin cells that are overproduced when a patient has psoriasis (28). Despite a few non-human laboratory studies, I was unable to find any studies on CBD oil use in human subjects with skin conditions.

Bottom Line

The research on CBD oil for skin conditions is very limited and we don’t know if it is helpful in humans.

Is CBD Oil Safe?

CBD oil seems to be safe and is generally well-tolerated (2). Some of the most common side effects that patients reported were tiredness, diarrhea, and changes in appetite and weight (9). In addition, one review on all types of cannabinoids found that in 79 studies, the most commonly reported adverse events were “asthenia [weakness], balance problems, confusion, dizziness, disorientation, diarrhea, euphoria, drowsiness, dry mouth, fatigue, hallucination, nausea, somnolence, and vomiting” (27). The authors suggested that the side effects they found were not strongly asscociated with any one type of cannabinoid but given that cannabidiol is often paired with other types, it is important to keep in mind other side effects.

However, as one author points out, we need to have longer-term studies with higher numbers of patients in order to complete our knowledge (9).

We still do not know the effects of long-term CBD use, its interactions with other drugs, or its effects on other systems of the body. If you are interested in CBD oil, you should consult your doctor.

Conclusion

The scientific research behind CBD is limited to studies on cells in a lab or in animals, and few human trials exist. There is some strong evidence that CBD oil may help with epilepsy and anxiety. However, any claims suggesting it can help with pain, depression, weight loss, inflammation, or cancer are not based on strong science and are likely an exaggeration of a non-human study designed to sell you something.

CBD oil may have some potential uses, but the science is currently lacking for the majority of claims surrounding it. I hope we see more solid scientific research on CBD in the future.