Cannabis is used for a wide range of purposes, from treating specific medical conditions to everyday relaxation and sleep. Among people who use cannabis, roughly 59% report using it for relaxation, 47% for enjoyment, and about 31% for medical reasons like pain relief. On the medical side, the evidence base has grown enough that the U.S. Department of Health and Human Services has recognized a currently accepted medical use for cannabis, with more than 30,000 licensed healthcare practitioners across 43 U.S. jurisdictions now authorized to recommend it for over 6 million registered patients.
How Cannabis Works in the Body
Your body has a built-in network of receptors that respond to cannabinoids, the active compounds in cannabis. The two main receptor types, CB1 and CB2, are distributed throughout your body and serve different roles. CB1 receptors are among the most abundant receptors in the brain, concentrated in areas that control movement, memory, cognition, and pain perception. They sit at nerve endings and work by dialing down the release of chemical messengers between nerve cells, which is why cannabis can reduce pain signals, alter mood, and affect coordination.
CB2 receptors are found primarily in immune cells and tissues outside the brain. They play a larger role in inflammation and immune response. Interestingly, CB2 receptors appear to become more active in diseased brain tissue, including in conditions like Alzheimer’s disease and multiple sclerosis, which is one reason researchers are interested in cannabis for neurological and inflammatory conditions.
Chronic Pain
Pain relief is the most common medical reason people turn to cannabis, and it’s one of three uses for which the FDA has found credible scientific support. Across clinical trials, cannabinoids produce a modest but measurable reduction in chronic pain compared to placebo: 37% of patients using cannabinoids reported meaningful pain relief versus 31% on placebo, with an average drop of about 0.4 points on a 10-point pain scale.
The results look stronger for specific pain types. In trials of HIV-related nerve pain, 52% of people using inhaled cannabis reported at least a 30% reduction in pain, compared to 24% on placebo. For fibromyalgia, patients on THC treatment reported an average pain reduction of about 5 points on a visual scale. A cross-sectional study of migraine patients found that 61% of those using cannabinoids cut their monthly migraine frequency by more than half. Patients with multiple sclerosis-related muscle spasticity and pain reported a 61% reduction in symptoms with cannabis extract, compared to 46% with placebo.
Expert panels generally recommend starting with a CBD-dominant product and adding THC only as needed, beginning at 2.5 mg or less and increasing slowly up to a ceiling of about 40 mg of THC per day. Individual responses vary considerably, and starting too high can cause more problems than it solves.
Epilepsy and Seizure Disorders
The strongest regulatory endorsement for cannabis in medicine belongs to a purified CBD medication approved by the FDA for three severe seizure disorders: Dravet syndrome, Lennox-Gastaut syndrome, and tuberous sclerosis complex. These are rare, treatment-resistant conditions that often begin in childhood and can cause dozens of seizures per day.
In a major clinical trial for Dravet syndrome, children taking CBD saw their monthly convulsive seizures drop from a median of 12.4 to 5.9, a 39% reduction. The placebo group saw only a 13% reduction. That 26-percentage-point gap is significant for families dealing with a condition where standard medications often fail. The medication is approved for patients as young as one year old.
Chemotherapy-Related Nausea and Vomiting
Cannabis has been used for nausea since long before formal clinical trials existed, and this remains one of its best-supported medical applications. The FDA has approved synthetic THC-based medications specifically for chemotherapy-induced nausea and for appetite loss in AIDS patients.
A randomized trial published in the Journal of Clinical Oncology tested an oral cannabis extract containing both THC and CBD against placebo for chemotherapy nausea. The complete response rate, meaning no vomiting and no need for rescue medications, was 24% for cannabis versus 8% for placebo. Patients in the cannabis group also vomited less frequently (averaging 0.2 episodes per day versus 0.5) and reported significantly lower nausea scores. These numbers may sound modest in absolute terms, but for patients already on standard anti-nausea drugs who are still struggling, tripling the complete response rate represents a meaningful improvement in quality of life during treatment.
Anxiety, Sleep, and Stress
Among recreational and self-medicating users, stress relief, coping with anxiety, and improving sleep are some of the most frequently cited reasons for using cannabis. In survey data, 35% of cannabis users reported using it to cope with stress and anxiety, and about 30% used it specifically for sleep.
The relationship between cannabis and anxiety is complicated. At low doses, THC can reduce anxiety for many people. At higher doses, it can trigger or worsen anxiety and even cause paranoia. This dose-dependent flip is one of the most consistent findings in cannabis research, and it’s why recommendations for anxiety consistently emphasize starting below 2.5 mg of THC. CBD, by contrast, does not appear to cause anxiety at higher doses and has shown anxiolytic effects in some studies, though it is not FDA-approved for this purpose.
For sleep, the evidence is strongest in people who have trouble sleeping because of another condition, particularly chronic pain. Cannabis may help these individuals fall asleep faster and stay asleep longer, though whether it improves sleep quality in otherwise healthy people is less clear.
Recreational and Social Use
Most people who use cannabis do so for non-medical reasons. In a large cross-sectional study of Canadian workers, the top motivations were relaxation (59.3%), enjoyment (47.2%), and socializing (35.3%). These numbers reflect what most users already know: cannabis is widely used in the same social and personal contexts as alcohol, as a way to unwind, enhance experiences, or connect with others.
Risks and Side Effects
Cannabis is not without downsides, and the risks tend to scale with how much and how often you use it. Short-term effects can include impaired memory and coordination, increased heart rate, dry mouth, and at higher THC doses, anxiety or paranoia.
One condition unique to heavy, long-term cannabis users is cannabinoid hyperemesis syndrome, a disorder marked by cycles of severe nausea, vomiting, and abdominal pain that repeat every few weeks to months. It typically develops after several years of regular use and resolves only when cannabis use stops completely, confirmed by a negative drug screen. The condition can mimic other causes of cyclical vomiting, with patients sometimes experiencing 12 to 15 vomiting episodes per day during acute bouts. Many people with this condition find temporary relief in hot showers or baths, which is considered a hallmark clue for diagnosis.
Regular use can also lead to dependence, where stopping causes irritability, sleep disruption, and decreased appetite for a period of days to weeks. The risk of psychological dependence is a key reason that even the federal rescheduling recommendation placed cannabis in a category acknowledging “high psychological dependence” potential. Cognitive effects from heavy use during adolescence, when the brain is still developing, are a particular concern, with some evidence of lasting impacts on memory and executive function.
The Legal and Regulatory Landscape
Cannabis currently sits in a transitional space. As of 2023, the Department of Health and Human Services recommended moving cannabis from Schedule I (no accepted medical use, high abuse potential) to Schedule III (accepted medical use, moderate to low physical dependence potential). That recommendation was based on the FDA finding credible scientific support for cannabis in treating pain, appetite loss related to certain medical conditions, and chemotherapy-induced nausea and vomiting. The rescheduling process is still underway, and cannabis remains federally classified under its original schedule even as 43 state-level jurisdictions operate their own medical cannabis programs.