CBD Oil: The Science Behind This Cannabis Plant Extract

Cannabidiol (CBD) is a cannabinoid that is mixed with a carrier oil to make CBD oil.

Cannabinoids act on the body's endocannabinoid system to regulate anxiety, mood, and appetite. CBD is extracted from cannabis plants (e.g., Cannabis indica, Cannabis sativa, and Cannabis ruderalis). However, the hemp plant (Cannabis ruderalis) typically contains higher quantities of CBD.

The other main component of Cannabis indica and Cannabis sativa species—but not typically Cannabis ruderalis—is delta-9-tetrahydrocannabinol (THC).

THC can cause a sense of euphoria but can also cause other sensations, like paranoia. CBD oil should not contain more than 0.3% THC, so it does not typically cause a feeling of euphoria—so many people assume it's safe, although it may not be, especially for specific populations.

CBD products are of interest to researchers and consumers. One source projected that the products may make more than $20 billion in the United States alone by 2024. CBD has been studied for its use in seizures, chronic pain, anxiety, inflammation, and more. However, varying levels of scientific evidence exist for these claims, meaning it's unclear if CBD works for these conditions.

Note that CBD oil is different from hemp oil. Hemp oil is processed differently (pressing hemp seeds) and typically contains no CBD.

This article covers the latest evidence on over-the-counter CBD—its uses, interactions, and what to know before you try it.

CBD Oil Benefits

Proponents of CBD oil claim that it benefits people with various health problems. As CBD has gained popularity, researchers have been trying to study it more—but, so far, human trials remain sparse. There is little evidence to support its myriad health claims. 

Here's a deeper dive into CBD oil's more compelling health benefits.

Supports Brain and Nerve Conditions

In June 2018, the FDA approved a CBD oral solution called Epidiolex. Epidiolex is a prescription drug, not an over-the-counter (OTC) product.

Epidiolex is used to treat two rare forms of epilepsy in children under 2 years: Dravet syndrome and Lennox-Gastaut syndrome. These rare genetic disorders cause lifelong seizures in the first year of life. It’s also approved for use in tuberous sclerosis complex, a rare genetic condition that causes benign tumors to grow throughout the body, often accompanied by seizures.

Keep in mind that Epidiolex is not a supplement. It requires a prescription from a healthcare provider. 

CBD has also been studied for the following:

• Autism spectrum disorder
• Depression
• Parkinson's disease

While promising, further research is needed for these conditions. And over-the-counter CBD products are not regulated or standardized like prescription medications such as Epidiolex. 

May Help Treat Anxiety

CBD might help treat anxiety disorders, although there have not been many trials to look at CBD's anxiety-relieving effects in humans.

In one study, 57 men took either CBD oil or a sugar pill with no CBD (placebo) before a public-speaking event. The researchers assessed the participants' anxiety levels using blood pressure and heart rate measures. The researchers also used a reliable test for mood states called the Visual Analog Mood Scale.

The men who took 300 milligrams (mg) of CBD oil reported less anxiety than the men who were given a placebo; however, the men who took 100 or 600 mg of CBD oil did not experience the same effects. This trial was limited by a small sample size and only enrolled men, so more data is needed to see if CBD has a similar impact on women.

In another double-blind placebo-controlled study (meaning neither participants nor researchers knew who took the substance and who took a placebo), CBD was also shown to decrease symptoms of Social Anxiety Disorder in teenagers. This study was well-designed but very small; only 37 people were studied.

May Assist Substance Use Disorder Treatment

CBD may be able to inhibit the rewarding and reinforcing effects of addictive substances (e.g., tobacco, cocaine, methamphetamine (METH), heroin, and morphine). While the preliminary research is promising, more is needed to confirm results. 

Might Help Treat Schizophrenia

In a randomized controlled trial of 88 people already taking medication for schizophrenia, 1,000 milligrams per day of CBD oil decreased positive psychotic symptoms (hallucinations or delusions). However, there were no significant differences between CBD oil and placebo regarding negative psychotic symptoms (like blunt affect or disinterest in others).

Also, note that CBD oil was studied as an add-on therapy here since the people in the trial were already taking prescription medicines to treat schizophrenia.

Products with significant amounts of THC may worsen symptoms of psychosis, schizophrenia, and paranoia.

May Support Sleep

There is conflicting evidence to support the use of cannabinoids to treat sleep disorders. Although some study outcomes have been favorable, most have not.

For example, a 2022 comprehensive review of the effects of cannabinoids on normal sleep and sleep disorders showed that cannabis products have minimal to no effects on sleep and may produce negative effects in some individuals. 

A 2017 study found that CBD products containing THC may decrease the time needed to fall asleep. but could also impair sleep quality in the long term. And, a 2021 meta-analysis on CBD's effects as an appetite suppressant and as a sleep aid concluded that, while there was a moderate positive impact on appetite control, CBD showed no effect on sleep.

May Lower High Blood Pressure

CBD may produce favorable outcomes for people attempting to lower their blood pressure. Multiple recent studies have shown CBD's effectiveness in reducing blood pressure in those with hypertension.

Accumulated data (both from human and animal studies) suggest that CBD may be associated with improved cardiovascular function, marked reductions in blood pressure, and enhanced endothelial function.

Although the data is preliminary, CBD oil has also been studied for the following uses:

• Acne
• Arthritis
• Chronic pain
• Digestive disorders
• Skin conditions (e.g., eczema or psoriasis)

There’s not enough data to recommend CBD oil for any of these uses quite yet.

What Are the Side Effects of CBD Oil?

Clinical research has shown that CBD oil can cause side effects. In one study, 91% of people with seizure disorders who took the prescription product Epidiolex had side effects from the medicine. The specific side effects and their severity vary from one person to the next and from one type of CBD to another.

Common Side Effects

The most common side effects of CBD oil that were reported include the following:

• Change in appetite
• Drowsiness or fatigue
• Diarrhea
• Change in liver enzymes

Severe Side Effects

Severe side effects have been noted in people with treatment-resistant epilepsy (ongoing seizures despite multiple medications). These include:

• Status epilepticus (a life-threatening medical emergency where a seizure lasts longer than five minutes)
• Pneumonia (infection of the air sacs in the lungs)

Also, consider that CBD products are not regulated and may be adulterated or labeled misleadingly. One study found that 21% of CBD products sold online also had THC. Severe side effects of THC, particularly at doses above 2.4 mg, can be quite severe and include:

• Anxiety
• Impaired cognition (lowered IQ scores and memory loss)
• Psychosis (including suspiciousness, emotional withdrawal, and hallucinations)

If you notice these effects while using CBD oil, discontinue and discuss side effects with a healthcare provider as soon as possible.

Adolescent users are at increased risk of psychological disorders from THC. These psychological disorders include an increased risk of psychosis and schizophrenia.

Precautions

Your healthcare practitioner may advise against using CBD oil if you:

• Have liver disease: CBD oil may increase liver enzymes, a marker of liver inflammation. Talk with your healthcare provider before taking CBD oil. You may need to check your liver enzymes regularly if you use CBD.
• Have eye issues: CBD oil may also cause eye-related side effects. A 2018 study found that it may increase pressure inside the eyes. For people with glaucoma, this can make the condition worse. Some people also report dry eyes as a side effect of CBD oil.
• Are pregnant or nursing: You should not use CBD oil if you're pregnant or breastfeeding. Even though the effects of CBD are not fully understood, it does pass through the placenta. The American Academy of Pediatrics (AAP) further states that pregnant people should not use marijuana products because of the potential risks to developing fetuses.
• Drink alcohol or take other sedating medications: Using CBD with these drugs could cause excess drowsiness.
• Are a child: Children should not use CBD oil.
  

Dosage: How Much CBD Oil Should I Take?

There are no guidelines for CBD products or a "correct" dose of CBD oil. CBD has been used in doses ranging from 40 to 1,280 mg per day. For example, in one trial, patients admitted to the emergency room for acute back pain were given a one-time dose of 400 mg of CBD oil.

In another trial, schizophrenic patients were given 600 mg per day of CBD oil for six weeks. As a general rule, never take more than the recommended dose.

What Happens if I Take Too Much CBD?

Doses of up to 1,400 mg per day seem well-tolerated in adults. Keep an eye out for serious side effects like fatigue, changes in appetite, seizures, or pneumonia. Also, be aware that CBD may be adulterated (containing unlisted ingredients such as THC) and may not contain the amount of CBD listed on the bottle.

Children can be especially vulnerable. Dangerously slowed breathing has been noted in a pediatric case report of a child who unintentionally ingested too much CBD.

CBD is also found in many foods and drinks in the U.S., so if you plan to consume these, discuss your total daily dose with your healthcare provider.

If you have questions or concerns about the use or unintended (accidental) ingestion of CBD products, contact your healthcare provider, health department, or local or regional Poison Control Center at 800-222-1222. Call 911 in case of emergency.

Interactions

CBD oil can interact with medications, including many used to treat epilepsy. One of the reasons for this has to do with how your body breaks down (metabolizes) drugs.

Cytochrome P450 (CYP450) is a liver enzyme your body uses to break down some drugs. CBD oil is broken down by and can also affect  CYP450. That means taking CBD oil with these drugs could have a more substantial effect than you need or make them not work as well.

Drugs that could potentially interact with CBD include:

• Anticonvulsants like phenobarbital, Lamictal (lamotrigine), Onfi (clobazam), Dilantin (phenytoin), Tegretol (carbamazepine) and Trileptal (oxcarbazepine). In general, these will decrease the level of CBD. CBD increases lamotrigine levels.
• Antidepressants like Paxil (paroxetine), Celexa (citalopram), Remeron (mirtazapine), and Tofranil (imipramine). CBD may increase the levels of these medicines and exacerbate their side effects.
• Antifungals like ketoconazole
• Antipsychotics like Haldol (haloperidol)
• Benzodiazepine sedatives like Klonopin (clonazepam), Ativan (lorazepam), and Valium (diazepam). CBD decreases the effect of clonazepam and increases the impact of the others, which may increase side effects like drowsiness.
• Echinacea species 
• Erectile dysfunction drugs like Viagra (sildenafil)
• Immune-suppressants like Sandimmune (cyclosporine). CBD may increase the levels of these drugs.
• Macrolide antibiotics like clarithromycin 
• Opioid painkillers like morphine. CBD increases the effect of morphine.
• Rifampin-based drugs used to treat tuberculosis.
• Statins to treat cholesterol like Lipitor (atorvastatin) and Zocor (simvastatin)

Always tell your healthcare provider and pharmacist about all your medicines, including prescription, OTC, herbal, or recreational drugs. Alcohol or other recreational drugs that cause drowsiness may have increased side effects if used with CBD oil.

The interactions between these medications and CBD may be mild, and you might not have to change your treatment. However, in some cases, you might have to change drugs or space out your doses to avoid a reaction. Never change or stop medication without talking to your provider.

It is essential to carefully read a product's ingredient list and nutrition facts panel to know which ingredients and how much of each ingredient is included. Please review this supplement label with your healthcare provider to discuss potential interactions with foods, other supplements, and medications.

Sources of CBD Oil and What to Look For

CBD can be derived from two types of cannabis plants: marijuana, which has a higher amount of THC, and hemp, which has a low amount of THC. Since 2018, the FDA has allowed CBD products to be sold as long as they have less than 0.3% THC. The FDA has made it illegal for companies to market CBD as dietary supplements or to claim that they treat specific conditions.

Remember that CBD oils are unregulated. There's no guarantee that a product is what it claims to be on its packaging. You also can't know for sure that it's safe and effective. 

Summary

The FDA does not regulate CBD oil, and contrary to popular opinion, it does come with some risks. Until more research is done on CBD oil, it's important to remember that it may not live up to the hype and could even be dangerous. CBD products have not shown strong evidence of benefit for most of the advertised conditions.

There is significant variability among the products you'll find at dispensaries, smoke shops, or online. Each product can contain very different amounts of CBD or THC than what's listed on the package and can also contain harmful additives.

If you choose to use CBD oil, always discuss it with your healthcare provider to ensure it doesn't interact with your prescription medications. CBD is not appropriate for pregnancy, breastfeeding, or in children.