CBD and its effects: What really happens in the body

Key takeaways

• CBD works via the body’s own endocannabinoid system and influences pain, inflammation, and mood
• The effects kicks in between 15 minutes and 2 hours, depending on how it’s used
• CBD is not psychoactive and, unlike THC, it doesn’t make you “high”
• Scientific studies show effectiveness for epilepsy, anxiety disorders, and chronic pain
• Side effects are rare and usually mild, but interactions with other medications are possible

Cannabidiol, better known as CBD, has sparked huge interest in medical research and among consumers in recent years. This active compound from the hemp plant promises therapeutic benefits without the intoxicating effects of cannabis. But how does CBD effects actually work in the human body, and what does current science say about it?

In this in-depth article, we take a closer look at the mechanisms through which CBD affects our body, examine proven therapeutic uses, and share practical tips for safe use. We base this on current studies and research findings to give you a solid foundation for making informed decisions.

What is CBD and how does it work?

Cannabidiol is a main component of the cannabis plant (Cannabis sativa and Cannabis indica) and belongs to the class of phytocannabinoids. Unlike tetrahydrocannabinol (THC), CBD has no psychoactive or intoxicating properties. The abbreviation stands for a chemical compound that, as a lipophilic molecule, can be taken orally, sublingually, by inhalation, or applied topically.

The crucial difference between CBD and THC lies in how they work: while THC binds directly to CB1 receptors in the brain and triggers psychoactive effects, CBD acts through various other mechanisms in the endocannabinoid system. This substance shows a wide range of potential effects on the human body without causing the typical “high” feeling.

The endocannabinoid system is a complex network of receptors, enzymes, and endogenous cannabinoids that plays an important role in regulating various physiological processes in our body. The two main receptors are:

• CB1 receptors: Located mainly in the central nervous system
• CB2 receptors: Found primarily in the immune system and peripheral tissues

However, CBD shows low affinity for both classic cannabinoid receptors. Instead, it acts as an inverse agonist at the CB2 receptor and interacts with various other receptor systems in the body.

How CBD works in the body

The CBD effects unfolds through several complex mechanisms that go far beyond the endocannabinoid system. At the TRPV1 receptor, CBD shows a effects similar to capsaicin, which suggests possible effects on neuropathic pain. This interaction could explain why some people experience pain relief.

On top of that, CBD interacts with μ and δ opioid receptors as well as serotonergic 5-HT1A receptors. The latter are suspected to be relevant for the antidepressant and anxiolytic effects of CBD. As an antagonist at the GPR55 receptor, it has further potential effects, for example on blood pressure and calcium regulation.

However, the oral bioavailability of CBD is relatively low, at around 6–19 percent. This is mainly due to extensive hepatic metabolism via the first-pass effect. The body breaks down CBD primarily in the liver, so that only a fraction of the amount taken actually reaches the bloodstream.

Influence on neurotransmitters and bodily functions

CBD influences various neurotransmitter systems and can therefore have effects on:

• Pain perception: Through interaction with pain receptors
• Immune system: Modulation of inflammatory processes
• Sleep–wake cycle: Influence on melatonin production
• Mood regulation: Activation of serotonin receptors

Studies show that CBD affects the release of cortisol, the main stress hormone. An interaction with cortisol secretion after stressful situations has been observed in humans, which could explain the relaxing effects of the substance.

Proven therapeutic effects of CBD

Scientific research has demonstrated concrete therapeutic effects of CBD in several areas. The strongest evidence is for the treatment of certain forms of epilepsy.

Antiepileptic effects

The approval of the first CBD-based medication, Epidiolex, by the FDA in 2018 marked an important milestone. The medication is approved for treating Dravet syndrome and Lennox–Gastaut syndrome – rare, severe forms of epilepsy. Randomized, controlled studies have shown clear efficacy in refractory forms of epilepsy.

Patients with these severe seizures, who do not respond to standard painkillers and other medications, showed a significant reduction in seizure frequency under CBD therapy.

Anti-inflammatory and pain-relieving properties

In pain management, however, the evidence is mixed. While animal experiments have shown anti-inflammatory and analgesic effects in joint wear and tear, a controlled human study by MedUni Vienna from 2023 with 86 patients suffering from severe knee osteoarthritis could not demonstrate a significantly better effects of orally administered, high-dose CBD compared to placebo.

Based on the current state of research, CBD is therefore not an evidence-based replacement for classic painkillers in clinical human medicine. However, research in this area is still ongoing.

Anxiolytic and mood-regulating effects

For anxiety and stress, studies are showing promising results. According to a cross-sectional study with 387 participants, most CBD users regularly report subjectively perceived improvements in stress, sleep, and anxiety even at low doses.

In placebo-controlled studies with pure CBD application in humans (usually doses up to 300 mg per day), positive effects on subjective well-being were found. However, robust, long-term clinical studies are rare and sometimes show conflicting results.

CBD for specific conditions

The use of CBD spans various health areas, with different levels of evidence.

Epilepsy and seizures

As already mentioned, the effectiveness for certain forms of epilepsy is the best documented. The Epidiolex studies showed a clear reduction in seizure frequency by an average of 25–40 percent compared to placebo in patients with Dravet syndrome and Lennox-Gastaut syndrome.

Anxiety disorders and depression

For anxiety disorders, several smaller studies point to positive effects. Activation of 5-HT1A receptors by CBD could be responsible for this anxiolytic effects. For depression, the data is still insufficient for definitive conclusions.

Chronic pain and arthritis

Despite the disappointing results of the Vienna arthritis study, many people report relief from chronic pain. A combination of THC and CBD is used, for example, for multiple sclerosis and chronic pain, where the side-effect profile needs to be assessed in a differentiated way.

Sleep disorders and other complaints

For sleep disorders, menstrual discomfort and general malaise, CBD is often used for self-medication. Practical examples are CBD oils, capsules, creams or foods such as gummies that are marketed with soothing effects.

Onset and duration of effects

The onset of effects of CBD strongly depends on the form of application. These factors influence both the speed and intensity of the effects:

Form of application	Onset of effects	Duration of effects	Bioavailability
Sublingual (oil)	15–45 minutes	4–6 hours	20–35%
Oral (capsules)	30–120 minutes	6–8 hours	6–19%
Inhalation	2–10 minutes	2–4 hours	25–60%
Topical (creams)	15–30 minutes	2–4 hours	Local

Sublingual absorption vs. oral intake

Sublingual absorption of hemp oil under the tongue partially bypasses the first-pass effect and leads to faster and more efficient uptake. The oil should be held under the tongue for about 30–60 seconds before swallowing.

With oral intake of capsules or other products, CBD first has to pass through the digestive tract and is metabolized in the liver, which leads to a delayed but longer-lasting effects.

Steady-state concept with regular intake

With regular use, a baseline concentration of CBD builds up in the body. This steady-state level is usually reached after 3–5 days of regular intake and can lead to a more consistent effects.

Dosage and intake recommendations

The right dosage of CBD varies a lot from person to person and depends on several factors. The basic principle is “start low, go slow” – start with a low dose and increase it slowly.

Individual factors in finding the right dose

The following factors influence the optimal CBD dose:

• Body weight: Heavier people often need higher doses
• Metabolic rate: Influences absorption and breakdown
• Severity of symptoms: Stronger complaints may require higher doses
• Tolerance: Can develop with long-term use
• Simultaneous use of medication: Can cause interactions

Recommended starting doses

For different uses, the following starting doses are recommended:

• General well-being: 5–10 mg daily
• Stress and anxiety: 10–25 mg daily
• Sleep disorders: 25–50 mg before going to bed
• Chronic pain: 25–50 mg daily
• Severe epilepsy: Only under medical supervision, often 100+ mg daily

Adjusting the dosage

The dose should be increased by 5–10 mg every 2–3 days until the desired effects is reached. It’s important to listen to your own body and reduce the dose if you notice unwanted side effects.

Maximum daily doses from studies in healthy adults are around 300–600 mg daily, and such high doses should only be used under medical supervision.

Side effects and safety

CBD is generally considered well tolerated but can still cause side effects. These are usually mild and dose-dependent.

Common side effects

The most commonly reported side effects include:

• Tiredness and drowsiness
• Dry mouth
• Dizziness
• Diarrhea
• Changes in appetite
• Nausea

Rare but serious side effects

From doses above 300–600 mg daily, the following have been observed more frequently:

• Liver-damaging effects (elevated liver values)
• Negative changes in the nervous system
• Hormonal disorders
• Gastrointestinal problems
• Impaired reproduction and fertility
• Safety profile in comparison

Compared to THC, CBD is not psychoactive and shows a better safety profile. Unlike many conventional medications, CBD does not lead to physical dependence or severe withdrawal symptoms.

Most people tolerate CBD well, but if side effects persist or are severe, you should see a doctor. Medical advice is especially important if you’re taking other medications at the same time.

Interactions with other medications

CBD can affect the effects of other medications because it inhibits certain liver enzymes that are responsible for breaking down many drugs.

Important drug classes with known interactions

Be especially careful with:

• Antiepileptics: Possible increase or decrease in effects
• Blood thinners: Increased risk of bleeding
• Cardiovascular medications: Changes in blood pressure
• Sedatives: Stronger sedative effects
• Immunosuppressants: Altered immune response

Importance of medical advice

Before taking CBD products, people who regularly take medication should definitely talk to their doctor. This is especially true for people with chronic conditions or complex medication plans.

Regular monitoring of blood values and the effectiveness of existing therapies may be necessary to detect unwanted interactions at an early stage.

Factors that influence CBD effects

Various factors can significantly influence the effectiveness and intensity of CBD.

Quality and purity of the CBD product

The quality of the hemp products used plays a crucial role. Factors such as:

• Extraction method (CO2 extraction is considered optimal)
• Level of contaminants (pesticides, heavy metals)
• Actual CBD content (often differs from the advertised value)
• Storage and shelf life

Full-spectrum vs. isolate products

Full-spectrum products contain not only CBD but also other cannabinoids, terpenes, and flavonoids from the plant. These can have synergistic effects (the so-called “entourage effect”).

CBD isolate contains only pure cannabidiol without other plant components. It’s neutral in taste and suitable for people who want to avoid other cannabinoids.

Genetic factors and enzyme activity

Individual differences in enzyme activity can influence how CBD is metabolized. People with certain genetic variants may break down CBD faster or more slowly.

Lifestyle and diet

• Food intake: CBD is absorbed better with fatty foods
• Smoking: Can influence enzyme activity
• Alcohol consumption: May potentially increase sedative effects
• Stress: Can reduce effectiveness

Current research and future prospects

Research on CBD is developing rapidly, with new studies on different areas of application.

Ongoing clinical studies

Current research focuses include:

• Psychiatric indications: Psychosis, anxiety disorders, PTSD
• Neurological diseases: Alzheimer’s, Parkinson’s, multiple sclerosis
• Supportive cancer therapy: Nausea, loss of appetite, headaches
• Formulation optimization: Increasing bioavailability

New areas of application under investigation

Scientists are investigating CBD’s potential for:

• Neurodegenerative diseases
• Inflammatory bowel diseases
• Skin conditions like acne and eczema
• Addiction disorders as therapy support

Limitations of current research

Despite growing interest, there are still considerable research gaps:

• Lack of large, placebo-controlled long-term studies
• Insufficient evidence in food-level dosage ranges (under 300 mg daily)
• Heterogeneity in study designs and populations
• Lack of standardization of products and dosages

The effectiveness of CBD in the typical food dose range has not been scientifically confirmed with certainty, while potential risks with high or long-term dosing should not be underestimated.

Regulatory developments

Legislation in the EU and the USA is increasingly distinguishing between medicinal products and over-the-counter products. Further tightening of regulations is expected to ensure consumer safety.

Large-scale, placebo-controlled long-term studies are needed so that CBD products can be validated and properly regulated either as medicinal products or as functional foods.