Medical Uses for THC, CBD, and CBN

Cannabis is having a cultural moment that has in some areas outpaced the science. Legalization has normalized use across generations, CBD products crowd the wellness aisle, and yet the biology underlying cannabis and cannabinoid compounds remains complicated and in many respects, still unresolved.

The science

Cannabis and cannabinoids are compounds from the cannabis sativa plant. The two main active ingredients are delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). THC is the psychoactive component that produces the “high” associated with marijuana use, while CBD does not cause intoxication. Although cannabis also contains dozens of other cannabinoids, THC and CBD are the most widely studied and clinically relevant, so this article focuses primarily on these two compounds. 

We’re also focusing on clinical applications rather than recreational. Because cannabis is still a schedule 1 substance in the United States, meaning it is illegal at the federal level, legal restrictions continue to hinder scientific study. While research is increasing as more states legalize cannabis for medical and adult recreational use, the field remains heavily regulated and the evidence base is still emerging. 

Cannabis products vary widely in their THC and CBD content, and these different ratios produce distinct effects. Cannabis can be consumed in various forms including smoking, vaping, oils, edibles, and topical applications.

Cannabis works by interacting with your body’s endocannabinoid system, a network of receptors found throughout the brain and body.

THC primarily activates CB1 receptors, which are concentrated in brain areas involved in memory, thinking, coordination, and pleasure. This produces both the therapeutic and intoxicating effects of THC. 

CBD works differently. CBD produces its effects—tamping down anxiety and inducing calm—primarily by activating serotonin receptors, which are involved in mood and anxiety, and TRPV1 channels, or receptors involved in pain and inflammation. This explains why CBD can have potential therapeutic effects without causing intoxication.

What the research shows

Sleep:

• THC: THC products may improve subjective sleep quality, particularly in those with insomnia or poor sleep. Effects on sleep architecture, however, remain unclear. Early studies suggested that in higher doses, THC may suppress REM sleep, while more recent studies at lower therapeutic doses show mixed or neutral effects.
  • The dose and frequency are key. Chronic heavy use of THC may be associated with lighter, more fragmented sleep, and upon stopping, users often experience sleep disturbance and worsened insomnia. 
  • Guidelines do not recommend cannabis for insomnia due to limited evidence, tolerance, and rebound insomnia risk.
• CBD: Despite the many sleep-focused CBD products on the market, the latest research suggests CBD alone has no significant effect on sleep quality. Some studies have shown mixed results, and in some cases there were positive findings when CBD was mixed with other compounds, but clinicians do not currently recommend it for insomnia.
  • Studies have looked at whether CBD can help people who have insomnia due to anxiety, but even there, CBD showed no difference compared to placebo. Experts say this may be hard to measure and research is ongoing.
• Cannabinol (CBN): Recent research shows more promising results for a different cannabinoid known as cannabinol. Some studies show CBN can improve subjective sleep quality and help people stay asleep by reducing the number of times they wake during the night. Unlike CBD, which is not psychoactive, CBN has low levels of psychoactive compounds. The research here is also newer, so more studies are needed. 

Nausea and vomiting (from chemotherapy):

• THC: THC has been proven to help people with cancer who have chemotherapy-induced nausea and vomiting. Two synthetic THC medications—dronabinol (sold as Marinol or Syndros) and nabilone (sold as Cesamet)—are approved by the United States Food and Drug Administration (FDA) for chemotherapy-induced nausea and vomiting that doesn’t respond to standard anti-nausea drugs. For people whose nausea doesn’t respond to standard medications, adding a combination of equal parts THC and CBD may help, though side effects like sedation, dizziness, and anxiety are more common.
  • Note that most older studies were conducted before modern anti-nausea regimens, so it’s unclear how cannabinoids compare to current best practices.
• CBD: Animal studies suggest CBD may also have anti-nausea effects, but this has not been tested in humans with cancer. 

Appetite and weight:

• THC: Dronabinol is FDA-approved for HIV/AIDS-related loss of appetite and weight loss in people who haven’t responded to other treatments. A randomized, double-blind, placebo-controlled study showed statistically significant improvements in appetite, though the overall quality of evidence is limited.
• CBD: This is not an area where CBD alone has been shown to help.

Chronic pain:

• THC/CBD: The evidence on THC for chronic pain is mixed, and even when studies have shown benefits, they are typically small. The American College of Physicians’ 2025 guidelines recommend against using THC as a first-line treatment for people with chronic pain not related to cancer because of meager benefits and the other risks.
  • Evidence for THC-dominant products (those that are high in THC and contain low amounts of CBD) is mixed. The synthetic formulation nabilone may moderately reduce pain severity, but dronabinol does not show clear benefit. 
  • Medications that have balanced THC to CBD ratios may slightly increase the proportion of patients reporting improvement, though the effect is still small and evidence is low.
• CBD alone: There is no clear evidence that CBD-dominant products provide pain relief. 

Mental health:

• THC: Evidence does not support THC-dominant cannabis for post traumatic stress, and Veterans Affairs guidelines recommend against using cannabis for this condition. When it comes to anxiety, depression, or ADHD, there is also insufficient evidence. Regular use of high-THC products—especially in adolescents and young adults—is linked to higher risks of psychosis, substance use disorder, and self-harm in those with mood disorders. 
• CBD: Emerging evidence suggests CBD may reduce anxiety symptoms in people with anxiety disorders, though the evidence base remains small and short-term.

Epilepsy:

• THC: There’s no evidence that THC can help with epilepsy.
• CBD: A pharmaceutical-grade CBD medication known as Epidiolex is FDA-approved for use in patients 1 year of age and older who have seizures associated with Dravet syndrome, Lennox-Gastaut syndrome, and tuberous sclerosis complex. In clinical trials, CBD reduced seizure frequency by 50% or more in these severe, treatment-resistant epilepsies. CBD can interact with other seizure medications, particularly clobazam, so close monitoring by your doctor is essential.
  • Evidence remains insufficient to recommend cannabis or cannabinoids for treatment for epilepsy in adults outside of these specific conditions.

Cognitive function and neurodegenerative disease:

• THC: THC impairs cognition in a dose-dependent manner, affecting memory, decision-making, and executive function, and the effects may persist beyond the time when you are high. Chronic heavy use is associated with worse cognitive performance, and adolescents who use cannabis regularly may experience small declines in IQ. Current evidence does not show that cannabis causes dementia, but research is limited, and caution is warranted in older adults and those at risk for cognitive impairment.
  • In multiple sclerosis, a combination THC and CBD mouth spray called nabiximols, which is used in the United Kingdom, Canada, and some European countries may reduce patient-reported spasticity, though it does not improve objective measures. It is not approved by the FDA.
• CBD: CBD, on the other hand, does not appear to impair cognitive performance. Human trials (75–1,000 mg) show minimal cognitive effects across populations including healthy adults, those with Parkinson’s disease, psychiatric disorders, and substance use disorders. In Parkinson’s disease, 75–300 mg may produce small improvements in daily functioning, but evidence that CBD improves cognition in humans remains limited.

Addiction:

• THC: The evidence for THC treating substance use is limited and most research shows it does not help.
  • The THC/CBD mouth spray nabiximols has shown some promise for reducing cannabis use, but more research is needed.
• CBD: There are several studies that show CBD may help reduce cravings and anxiety associated with opioid use disorder. CBD also shows promise for helping those with alcohol use disorder and cannabis use disorder, while results are mixed on whether it can help with nicotine.

Usage guidelines

If you’re considering cannabis for a medical condition, talk with your clinician about whether it makes sense for your specific condition, medical history, and other medications. You should also review possible drug interactions, particularly with sedatives, blood thinners, and other psychoactive medications.

Most cannabis products in the U.S. have not been approved by the FDA and may not be covered by insurance, so it’s important to know exactly what you’re taking—especially the THC and CBD content, which can vary widely across products. Some studies have shown widespread inaccuracy in the labeling of cannabinoid products, with both higher and lower amounts of CBD and THC than advertised. To check the contents, you can ask for a certificate of analysis (COA), which provides lab confirmation of the exact concentration by batch. Licensed dispensaries and most reputable online providers will offer this.  

There is no standard dosing for most conditions, so the general approach is to start low and go slow, especially with THC-containing products. The way cannabis is used also matters: smoking and vaping act quickly but wear off faster, while edibles take longer to work and last longer, increasing the risk of taking too much too soon.

• Safety: THC can cause dizziness, sedation, dry mouth, increased heart rate, and anxiety. It also impairs driving and other tasks requiring coordination or judgment, so you should avoid driving while using it. More serious risks include cannabis use disorder, motor vehicle accidents, and worsening of psychiatric symptoms, including psychosis, in vulnerable individuals. CBD is generally better tolerated, with fewer side effects, but can still interact with other medications. All cannabis should be avoided during pregnancy.
• Legality: In 2018, Congress made hemp legal as long as it has less than 0.3% THC, so if your CBD is under that limit, it is legal to buy. However, some states still have legal restrictions on possessing CBD. As of this year, 40 states and Washington D.C. allow medical use of cannabis products and 24 states plus D.C. allow recreational use, but it’s always important to be careful when traveling with cannabis products and check the laws of your destination. At the federal level in the U.S., THC is still illegal.

Bottom line

Cannabis and cannabinoids have clear evidence-based uses in only a few situations, most notably pharmaceutical-grade CBD for certain severe epilepsies and prescription THC medications for chemotherapy-related nausea and HIV/AIDS–related anorexia. Evidence for chronic pain, sleep problems, and anxiety show small potential benefits in the right people. Other conditions show mixed data. Always check with your care team before experimenting.