CBD (Cannabidiol) is a phytocannabinoid with medicinal properties derived from the cannabis plant (i.e. marijuana). Of all ~113 active phytocannabinoids, or plant-based chemical constituents within the cannabis plant, cannabidiol is most abundant and accounts for approximately 40% of the plant’s extract. Unlike other phytocannabinoids that induce intoxicating effects (e.g. THC or tetrahydrocannabinol), cannabidiol is devoid of psychoactive effects.
Moreover, of all the phytocannabinoids within cannabis, cannabidiol is understood to exhibit the most prominent medicinal effects. Many people use cannabidiol or “CBD oil” to treat a variety of medical conditions, including: chronic pain, multiple sclerosis, drug addiction, anxiety disorders (read more: “CBD oil for anxiety“), schizophrenia, epilepsy, and chronic inflammatory disorders. When administered at proper dosages with professional medical instruction CBD is considered a safe substance, however, some individuals may be prone to experiencing CBD side effects and/or adverse reactions.
Cannabidiol (CBD) Side Effects & Adverse Reactions (List)
Included below is a comprehensive list of CBD side effects that persons who ingest cannabidiol might experience. Understand that the side effects experienced while using CBD are often subject to significant individual variation among users. For this reason, the specific side effects, severities of each side effect, and total number of side effects that you experience while using CBD – will be unique to you; not all users will share your experience.
That said, the most commonly reported CBD side effects include: tiredness, diarrhea, dry mouth, appetite reduction, and weight changes. If you have questions about CBD side effects, adverse reactions, or interactions, it is recommended that you consult a medical doctor.
Appetite reduction: While it’s widely known that “THC” can stimulate appetite and give users the “munchies,” most people won’t become ravenously hungry on CBD. In fact, evidence from both human and animal research suggests that cannabidiol (CBD) reduces or suppresses appetite. For this reason, you may notice that you’re not as hungry as usual and might even end up losing weight as a result of consuming fewer calories than usual (due to your reduced appetite).
Research by Morgan et al. (2010) suggests that CBD administration attenuates THC-induced appetite increases in humans smoking their favorite cannabis strains. It was hypothesized that CBD modulates appetite by mitigating the “wanting” and “liking” of food. These effects might be mediated by CBD’s action on CB1 receptors whereby it functions as a negative allosteric modulator. (Source: https://www.ncbi.nlm.nih.gov/pubmed/20428110).
Brain fog: While using CBD, you may experience the side effect of impaired clarity of thought, sometimes referred to as “brain fog.” More specifically, it may seem as though you’re spaced out and/or that your thought speed is exceptionally. It is suspected that brain fog occurring as a side effect of CBD is related to downregulation of the sympathetic nervous system and/or upregulation of the parasympathetic nervous system.
In most cases, the greater the dosage of CBD that you administer, the more likely you’re going to experience some brain fog, along with drowsiness, and/or cognitive impairment. Decreased production of stimulatory hormones, neurotransmitters, and brain waves may also explain the brain fog that emerges while using CBD. That said, do not assume that everyone experiences foggy thinking as a side effect of CBD.
Cognitive impairment: If you’re familiar with the Yerkes-Dodson law, you should know that physiologic arousal influences cognitive function. Individuals who are either excessively aroused (i.e. overstimulated) or suboptimally aroused (i.e. understimulated) will experience cognitive impairment. In some cases, CBD may enhance cognitive function by decreasing heightened arousal such as in a person with an anxiety disorder.
However, CBD could also cause cognitive impairment as a side effect if it ends up reducing arousal to the extent that you become drowsy. While under the influence of CBD, you might have a difficult time concentrating, memorizing things, learning new material, problem solving, or thinking critically. If you experience cognitive impairment from CBD, use it at times when you aren’t performing cognitively-demanding tasks.
Depression: The action of CBD across multiple neurotransmitter systems coupled with its ability to decrease systemic inflammation – sometimes makes it an efficacious intervention for depression. That said, some individuals might actually experience depression as a side effect of CBD. Any depression that occurs as a side effect may result from a neurochemical incompatibility with CBD, such that a user’s brain chemistry doesn’t react well to CBD’s neuromodulation.
Moreover, depression that emerges after using CBD could be due to downregulation of CNS activation. When CNS activity is downregulated, most individuals tend to experience fatigue, lethargy, and may be prone to bouts of depression. If you become depressed while using CBD, you may want to try reducing your dosage. Individuals with a history of neuropsychiatric disorders may be at highest risk of experiencing this side effect.
Diarrhea: In trials of CBD for epilepsy and psychotic disorders, one of the most common side effects of cannabidiol was diarrhea. Though it isn’t fully understood as to why diarrhea occurs as a side effect of CBD, it may be possible to prevent diarrhea with concurrently administered substances (e.g. Imodium). For this reason, if you experience an upset stomach, gastrointestinal distress, and diarrhea as a CBD side effect – ask your doctor whether it would be safe to try over-the-counter Imodium or another antidiarrheal agent along with CBD.
Dizziness: After ingesting CBD, you may experience a bit of dizziness as a side effect. The dizziness could be related to changes in: cerebral blood flow, neurotransmission, autonomic nervous system (ANS) activation, and/or reduced blood pressure. If you become dizzy while under the influence of cannabidiol, it is recommended that you evaluate your blood pressure.
The inhibitory effect of CBD upon the CNS may cause blood pressure to drop whereby you become dizzy and/or lightheaded. In some cases, dizziness may be a temporary side effect of CBD that new users experience during their first few weeks of treatment as their bodies adapt to the substance. If your dizziness is severe, you may want to evaluate your CBD dosage, its purity, and/or whether it might be interacting with another substance you’re using.
Dry mouth: Cannabidiol is understood to cause dry mouth or xerostomia in a subset of users. It is known that there are cannabinoid receptors in human salivary glands. CBD may interact with salivary cannabinoid receptors in ways that decrease or suppress salivary production, ultimately causing you to experience dry mouth, colloquially referred to as “cotton mouth,” while under its influence.
If you regularly experience dry mouth as a side effect of CBD, it is recommended that you stay hydrated, try over-the-counter dry mouth remedies, or chew sugar-free gum (to stimulate saliva production). Moreover, because dry mouth can increase concentrations of unfavorable bacteria in the mouth (which can cause cavities), regular dental check-ups are recommended for individuals with this side effect.
Heart rate change: Some individuals may notice that their heart rate changes while using CBD. Because most people find CBD to promote calmness, relaxation, and drowsiness – it’s common to experience lower blood pressure and a slowing of heart rate while under its influence. However, not everyone will experience decrease heart rate while using CBD – some might notice increased heart rate.
Increased heart rate could occur in a subset of CBD users due to dosing and/or stimulating effects. For example, research by Nicholson et al. (2004) suggests that CBD may increase alertness in some individuals. If CBD is increasing alertness and/or arousal, it’s possible that this could yield heart rate increases. If you notice any major changes in your heart rate while using CBD and/or have a history of cerebrovascular conditions, discontinue CBD and get your heart checked out by a medical doctor.
- Source: https://www.ncbi.nlm.nih.gov/pubmed/15118485
Irritability: While many individuals find CBD to effectively counteract irritability via stress reduction, others may experience irritability as a side effect. Among those who become irritable while using CBD, it’s possible that the irritability may stem from a neurochemical incompatibility with cannabidiol such that the user’s preexisting neurochemistry doesn’t respond well to CBD’s actions – ultimately triggering irritability, moodiness, and/or depression.
That said, the most likely cause of irritability while using CBD is downregulation of arousal and stimulatory neurotransmission. Some individuals may become frustrated with the resulting drowsiness, brain fog, and/or cognitive deficits that are attributable to decreased arousal from CBD, ultimately triggering irritability. Persons with preexisting neuropsychiatric disorders may be more prone to irritability as a side effect due to preexisting neurochemical abnormalities.
Insomnia: Though most individuals find CBD to induce relaxation whereby it becomes easier to fall asleep and/or cope with insomnia, others may [counterintuitively] find that CBD actually causes insomnia. A study by Nicholson et al. (2004) discovered that certain doses of CBD may exhibit alerting properties. This study reported that 15 mg of CBD increased alertness and counteracted sleep activity induced by THC. If you find that CBD is causing insomnia or impairing your sleep quality, you may want to try taking it in the morning rather than the late afternoon or evening. That said, if you’re already taking CBD in the morning, you may want to try taking it later in the day or adjust your dosing – as this may help with the insomnia.
- Source: https://www.ncbi.nlm.nih.gov/pubmed/15118485
Lightheadedness: Lightheadedness is another reported CBD side effect that may occur in a subset of users. It is suspected that lightheadedness could be related to a combination of decreased arousal, changes in cerebral blood flow, neurochemical modulation exerted by CBD, and/or low blood pressure. If you experience lightheadedness from CBD, it may be accompanied by dizziness and low blood pressure. Always check your blood pressure if you’re feeling lightheaded and sit or lie down somewhere comfortable to minimize likelihood of fainting.
Low blood pressure: In medical research, one of the most common CBD side effects reported was hypotension (low blood pressure). In many cases, the blood pressure lowering effects of CBD are considered therapeutic – especially among persons with a history of hypertension (high blood pressure). That said, if you have a history of low blood pressure or a medical condition that increases your risk of low blood pressure, it is recommended that you carefully monitor your blood pressure while using CBD. If your blood pressure drops too low as a side effect of CBD, this could result in dizziness, lightheadedness, and possible fainting (i.e. syncope).
Motor impairment: Individuals who use CBD on a regular basis and are well-adjusted to their dosage may not experience drowsiness or motor impairment while under its influence. However, persons who are new CBD users, high-dose CBD users, and/or are using CBD with other substances – may experience impaired motor function while under its influence. In most cases, the impaired motor function is a result of reduced activation of the sympathetic nervous system – which leads to drowsiness, sleepiness, and suboptimal alertness. For this reason, it is recommended that you abstain from operating a motor vehicle, heavy machinery, or engaging in any task that requires optimal motor function – while using CBD (especially high-potency CBD).
Tiredness or Drowsiness: Among the most common of all CBD side effects is tiredness, drowsiness, and/or somnolence. The tiredness is probably a result of CBD’s ability to downregulate activation of the sympathetic nervous system (SNS) and upregulate activation of the parasympathetic nervous system (PNS). Because CBD can cause tiredness, lethargy, and/or fatigue – many people administer it in the evening or before bed to enhance sleep. If you notice that CBD is making you tired, avoid taking it in the morning or before activities that require alertness and/or increased arousal such as: driving a vehicle; exercising; and/or working.
Tremors: Assuming you’re healthy without preexisting medical conditions, you’re unlikely to experience tremor, shakiness, or involuntary bodily movements as a side effect of CBD. However, if you have a preexisting neuropsychiatric disorder, you might experience tremor – or a worsening of tremor as an adverse reaction to cannabidiol. Research has shown that high-dose CBD administration can exacerbate tremor among a subset of persons with Parkinson’s disease. If you have Parkinson’s disease or another neuropsychiatric disorder in which tremor is a symptom, be cautious of using CBD – especially at high doses.
Weight loss: There are numerous anecdotes circulating around the internet reporting that daily administration of CBD oil resulted in weight loss. Though it is unclear as to whether CBD is an efficacious weight loss drug, there are plausible mechanisms by which cannabidiol (CBD) might facilitate weight loss. Research indicates that CBD ingestion: stimulates genes and proteins that augment fat oxidation; upregulates the number of mitochondria within the body (which can help expend calories); and downregulates the expression of proteins involved in lipogenesis (fat cell production).
The aforementioned physiologic effects, paired with decreased “wanting” and “liking” of food (via negative allosteric modulation of the CB1 receptor) may yield weight loss. Particularly, you may notice that your body has an easier time burning fat while using CBD and/or that your appetite is reduced (which yields decreased caloric intake). Therefore, it is not surprising that a subset of CBD users report weight loss.
Note: The above list of CBD (cannabidiol) side effects and adverse reactions may be incomplete. If you know of additional CBD side effects that weren’t documented above, be sure to share them in the comments section.
- Source: https://www.ncbi.nlm.nih.gov/pubmed/28861514
Variables that influence CBD side effects
There are a host of variables that likely influence the specific CBD side effects that you experience – as well as the severities of each side effect. These influential variables include things like: CBD dose (relative to body size and tolerance); administration specifics (e.g. modality); CBD specifics (e.g. sourcing); concurrent substance use; duration of CBD use; and individual factors (e.g. genetics). In most cases, the combination of these variables can be used explain differences in CBD side effects among CBD users.
CBD dosage (High vs. Low)
The dosage of CBD that a person uses relative to his/her body size and tolerance may determine whether side effects occur, and if they do, how severe they end up. In most cases, it is thought that side effects tend to be most severe and numerous among individuals using high doses of CBD relative to tolerance and body size. In fact, certain side effects such as tremor among individuals with Parkinson’s disease tend to only occur with high-dose CBD – but do not occur with low dose CBD.
Moreover, because high doses of CBD exert a more substantial effect upon physiology, it’s likely that side effects experienced at high doses will be more prominent or noticeable than at lower doses. For example, if you feel drowsy after using a low dose of CBD, doubling the dosage might amplify the drowsiness to a significant extent. At lower doses, less of the CBD is modulating physiology so users tend to experience fewer and/or less severe side effects.
CBD administration details
The administration specifics associated with your CBD use could influence the number and/or severity of side effects that you experience. Specifics that you may want to consider include: whether you took CBD on an empty or full stomach; modality of administration (e.g. sublingual); and administration timing (e.g. mid-afternoon). Someone who administers CBD sublingually on an empty stomach at night might have completely different side effects than if he/she administered CBD transdermally on a full stomach in the early afternoon.
- Empty vs. full stomach: Certain individuals may find that they experience a greater number of side effects and/or more severe side effects when taking CBD on an empty stomach. Yet others might report experiencing more total side effects when they use CBD on a full stomach. Nevertheless, your degree of fullness might impact the CBD side effects that you experience.
- Mode of administration: There are many different ways in which CBD can be administered. Mode of CBD administration can affect its bioavailability, metabolism, and ultimately influence the side effects that users experience. Administering CBD transdermally may minimize gastrointestinal side effects (e.g. diarrhea) because most of the CBD is absorbed locally. Realize that you might experience side effects with one modality of CBD administration that you wouldn’t with another.
- Timing: The time at which you administer CBD may influence your side effects or perception of them. It is known that there’s often a circadian rhythm interaction with substances. If you use CBD at night, you may find that it synergizes with your circadian rhythm to increase drowsiness to a greater extent than it would if administered in the morning. Understand that the time at which you use CBD may determine the side effects that you experience.
The specific attributes of the CBD formula that you administer, including: additives, brand, contaminants, potency, purity, sourcing, etc. – could determine whether you experience side effects. Administering a CBD formula containing additives (e.g. THC) or contaminants (e.g. pesticides) might increase risk of severe side effects and/or adverse reactions. Moreover, using CBD from one company (i.e. brand) might be of different purity and/or potency than CBD from another – even if dosages are listed as equivalent (listings aren’t always accurate)
- Additives: If you’re using pure CBD devoid of additives, you’ll probably experience fewer side effects than if you’re using a CBD formula with added substances (e.g. other phytocannabinoids or substances that modulate neurochemistry).
- Brand: Though there are many companies selling CBD online, not all of them retail a high-quality CBD product. Certain companies conduct zero quality control and simply cannot be trusted. Purchasing CBD from a reputable company should decrease risk of side effects compared to purchasing CBD from a company with an unknown or questionable reputation.
- Contaminants: Unless you’re personally testing the CBD that you order for quality, there’s a chance that it could contain contaminants. Ordering cheap CBD from countries outside of the United States may increase your risk of receiving a contaminated product. Contaminants such as pesticides and/or molds may be present in low-quality CBD products and cause side effects and/or adverse reactions as a result of toxicity.
- Potency & purity: The potency and purity of your CBD can influence whether or not you experience side effects. Utilizing a very potent CBD formula with high purity may increase risk of side effects due to the CBD exerting a more substantial effect upon physiology – than a less potent or lower purity CBD product.
- Sourcing: The sourcing of your CBD could also determine whether you’ll be at risk of experiencing side effects following its ingestion. Contact the company from whom you purchased your CBD to determine how their cannabis is cultivated, CBD is extracted, and whether there are any potential problems with their sourcing.
Concurrent substance use
It is understood that concurrent substance (medication, supplement illicit drug) use might influence the side effects that you experience while using CBD. Certain substances could exacerbate side effects of CBD or induce interaction effects, whereas others might attenuate certain side effects of CBD whereby it is easier to tolerate (than when used as a standalone). Because CBD may interact with hepatic CYP3A and CYP2C enzymes, any concurrently administered agent that undergoes metabolism via the aforementioned enzymes may yield a pharmacokinetically-mediated interaction effect and/or increase risk of side effects.
In addition, even if a concurrently-administered agent doesn’t pharmacokinetically-interact with CBD, there’s a chance that it could potentiate or modulate its neurochemical influence throughout the brain and central nervous system (CNS) to potentiate or attenuate certain side effects. For this reason, you should beware of the fact that concurrently-administered agents might be to blame for some of the side effects that you experience while using CBD.
Duration of CBD use
The total amount of time over which you’ve consistently administered CBD may influence the side effects that you experience. Over a short-term, individuals may be prone to experiencing CBD side effects as a result of their brain and/or body adjusting to the presence of the drug. With continued long-term use, many of these adjustment-related side effects that occur over the short-term will subside as the brain and/or body become adjusted to CBD treatment.
That said, although many adaptation-related side effects can abate with longer-term use of CBD, new side effects might emerge throughout long-term treatment. Long-term CBD use may cause tolerance and corresponding increases in dosage – each of which might yield new side effects. In any regard, know that side effects may change depending on how long you’ve consistently utilized CBD.
A myriad of individual factors such as: a CBD user’s genetics, lifestyle, and/or medical conditions could impact CBD side effects. Individuals who express certain genes, have certain medical conditions, and/or live unhealthy lifestyles – may be at greater risk of severe side effects and/or adverse reactions than healthy persons (without medical conditions) expressing other genes.
- Genetics: It is thought that having certain genes or expressing certain epigenetic signatures may influence the side effects that you experience on CBD. Genes that are implicated in CYP450 (cytochrome P450) metabolism may influence how quickly you metabolize CBD – as well as its side effects. Genetic variants in CYP3A or CYP2C enzyme expression might increase (or decrease) your risk of CBD side effects. Moreover, differences in genes that encode for cannabinoid receptor densities may determine CBD side effect risk.
- Lifestyle (diet, sleep, stress): Your lifestyle choices such as: diet, hydration, sleep quality, and stress level might influence the number and/or severities of CBD side effects. Someone who eats a poor diet, lacks proper sleep, and/or is under high stress – may experience unwanted side effects (partly attributable to poor lifestyle choices). Comparatively, someone who eats a balanced diet, maintains a low stress lifestyle, and gets adequate sleep – may find it easier to cope with CBD side effects.
- Medical conditions: Having certain medical conditions may increase your risk of side effects while under the influence of CBD. For example, it is known that individuals with Parkinson’s disease are at increased risk of experiencing tremor as a side effect of CBD – compared to others. This is because the neurochemical abnormalities implicated in Parkinson’s disease coupled with the neurochemical effects exerted by CBD may be partially incompatible. Other medical conditions like hypotension, cerebrovascular conditions, and neuropsychiatric disorders may increase risk of adverse reactions from CBD. Always consider that your medical diagnoses and medical history could increase your risk of CBD side effects.
CBD (Cannabidiol): Do the medicinal benefits outweigh the side effects?
If you’re regularly using CBD, you should evaluate whether the medicinal benefits derived from CBD administration outweigh the side effects that you’re experiencing during treatment. The majority of CBD users will experience medicinal benefits with a few side effects of modest magnitude. Moreover, a subset of CBD users will report significant medicinal benefit with zero unwanted side effects while using CBD.
Among those who derive medicinal benefit from CBD without problematic side effects, it makes sense to continue using the substance indefinitely under the guidance of a medical doctor. On the other hand, if you’re experiencing CBD side effects that interfere with aspects of your life, general health, and/or well-being – you may need to discontinue CBD – regardless of its medicinal effect. It doesn’t make logical sense to continue using a substance with side effects that you dislike or that endanger your health.
If you’re having a difficult time deciding whether CBD is more medicinal than problematic, it is recommended to document how you feel in a daily journal during your treatment. By documenting how you react to CBD each day in a journal, you’ll be able to look back at your journal after a month or two of treatment and know whether the medicinal effects outweighed the side effects; or vice-versa. Additionally, a journal will also provide documentation of side effects that you experienced, making it easier to explain your reaction to a medical doctor.
Possible ways to reduce CBD side effects
Listed below are some strategies that may prove helpful in decreasing the number of and/or the severities of CBD side effects. Realize that the effectiveness of these side effect mitigation strategies will be subject to significant individual variation. In other words, some people might find that these strategies are very helpful in reducing CBD side effects – whereas others might find them completely useless. Before implementing any of these side effect mitigation strategies, be sure to consult a medical doctor to verify that they’re safe and potentially useful.
- Alter CBD dosage: If you’re experiencing unwanted CBD side effects, you may want to try tweaking the dosage. Sometimes individuals experience side effects at lower doses that do not occur at higher doses; and vice-versa. Because high doses of CBD increase side effect risk, you may want to first try decreasing your CBD intake to the “minimal effective dose” – or lowest quantity needed to facilitate therapeutic benefit. Using a minimal effective dose may prove useful in facilitating medicinal effects without the bothersome side effects.
- Modify administration specifics: If you’ve tried modifying your CBD dosage but are still experiencing unwanted side effects, you may want to try taking altering CBD administration specifics such as: timing (morning vs. afternoon vs. evening); taking on a full vs. empty stomach; and modality of administration (sublingual vs. vaporization).
- Switch CBD brands: It is understood that certain CBD brands are less reliable than others in terms of manufacturing quality products. If you experience unwanted side effects with one brand – regardless of the dosage and/or administration specifics, you may want to try a different CBD brand or source. Not all CBD is created equal. If your CBD is contaminated (e.g. moldy) or contains unwanted additives, then switching to another brand may yield fewer side effects.
- Cease concurrent substance use: If you’re using other substances with CBD (or on the same day as ingesting CBD), you may want to discontinue all medically-unnecessary agents. As was mentioned, concurrent substance use can increase risk of CBD side effects and/or interaction effects. Discontinuing all medically-unnecessary substances may eliminate CBD side effects for some individuals.
- Add other substances: Although discontinuing medically-unnecessary substances may help reduce CBD side effects, adding other substances to your daily regimen could also counteract certain side effects. For example, if you’re experiencing unremitting diarrhea from CBD, you may want to try using an antidiarrheal agent (e.g. Imodium) to determine whether the diarrhea subsides. If you aren’t sure what substances are safe to use in effort to treat CBD side effects, ask a medical doctor.
- Continue using: If you’re a new CBD user, there’s a chance that the side effects you’re experiencing are due to lack of physiologic adaptation to CBD’s presence and/or effect. With continued usage, your physiology may adapt to the presence and/or effects exerted by CBD such that you no longer experience side effects stemming from lack of physiologic adaptation. For this reason, you may want to continue using CBD for a while (if you’re a new user) and reassessing whether side effects improve.
Note: If none of these interventions helps reduce your CBD side effects, you may need to discontinue CBD and ask a medical doctor about alternative therapies for your medical condition.
Have you experienced any CBD side effects?
If you’ve used CBD (cannabidiol) and have noticed side effects, share the specific side effects that you experienced in the comments below. Of the side effects that you experienced, document the severities of each side effect by rating them on a scale of 1 to 10 (with 10 being most severe). To help others get a better understanding of your situation, provide some details in your comment including: the brand of CBD that you use; your CBD dosage; your modality of CBD administration (e.g. inhalation, sublingual, transdermal, etc.); and the time of day at which you usually take CBD.
It may also be helpful if you’d mention things like: whether you use other substances with CBD (e.g. medications or supplements). If you take other substances with CBD or on the same days as CBD – have you considered that the side effects you’re experiencing may be caused by the other substance(s) or an interaction effect between the other substance(s) and CBD? Moreover, mention how long you’ve consistently used CBD as well as any medical conditions that may increase your risk of side effects.
Overall, you should realize that CBD is generally well-tolerated in most users and is unlikely to cause severe side effects or adverse reactions. That said, not everyone responds perfectly to CBD or finds it tolerable. If you find the side effects of CBD to be unbearable, work with a medical doctor and ask about alternative therapies.