How THC Works in the Brain

THC works in the brain mainly by activating CB1 cannabinoid receptors, the same receptors that the body’s own cannabinoids, such as anandamide, act on. Where those receptors sit shapes what THC changes, and NIDA notes that cannabis can cause altered time perception and impaired thinking, memory and body movement. The sections below go area by area.

THC comes from Cannabis sativa, the plant known colloquially as weed, pot, dope or ganja. Hemp is the same species grown with very little THC, mainly for fiber and seed oil, and under federal law, hemp has no more than 0.3% delta-9 THC by dry weight today; a 2026 law delays the new federal THC limits until at least December 11, 2026. First, a short look at how brain cells signal.

What Is the Endocannabinoid System?

Our brains are made up of neurons and neural circuits. Neurons do not touch one another, but they must communicate. To cover the gap between the neurons, our brain produces chemicals called neurotransmitters. These neurotransmitters deliver messages by passing from one neuron to another, where they attach to a special kind of molecule called a receptor. One family of these receptors is called cannabinoid receptors.

The body also makes cannabinoids of its own. These endocannabinoids, such as anandamide, act on these receptors and appear to have a role in pain, movement, appetite, mood and memory.

There are two primary cannabinoid receptors that have been identified by scientists:

• CB1 Receptors: these are mainly in the brain and nervous system, with some in other organs. THC acts on CB1 much like the body’s own anandamide, and activating CB1 is what produces the “high.”
• CB2 Receptors: these are found mainly on immune cells, and researchers study them for their role in inflammation.

Our body’s natural cannabinoids, like anandamide, help to regulate and react appropriately to incoming information. THC acts on the same receptors, so it changes signals the body normally controls itself. Which effects THC has depends on which CB1 receptors it activates, and where they sit.

CB1 receptors are found throughout the brain and nervous system. Each area below has its own job. The effect listed with each one comes from the linked source, which in most cases describes cannabis in general rather than that one area:

• Amygdala: the part of the brain that regulates emotions such as fear, pain, and anxiety. Anxiety, fear and distrust are more common with large amounts or high-THC products.
• Basal Ganglia: this part of the brain controls planning and starting a movement. Cannabis can slow reaction time.
• Brain Stem: this part of the brain sends information between the brain and spinal column. The FDA has approved dronabinol, a synthetic cannabis-related drug, for nausea and vomiting from chemotherapy; how much of that effect comes from the brain stem is not settled.
• Cerebellum: This regulates motor coordination and balance. Cannabis can impair body movement.
• Hippocampus: This is the learning center where new information is processed and stored for later. Cannabis can impair memory in the short term.
• Hypothalamus: This part of the brain helps control appetite. Increased appetite is a commonly reported effect of cannabis, and NCI notes that CB1 receptors here may be involved in the reward side of eating.
• Neocortex: This part of the brain presides over complex thought, feeling, and movement. Cannabis can impair thinking and alter time perception.
• Nucleus Accumbens: This is the motivation and reward center of our brain. Many people use cannabis to feel high, and it can make people feel happier or more relaxed.
• Spinal Cord: This transmits signals from the brain to other areas of the body. NCI notes that cannabinoids act on pain pathways here as well as in the brain and in nerves elsewhere in the body.

Why Does the Amount of THC Matter?

The effects of cannabis can vary greatly from individual to individual and are also dependent on the dosage as well as the delivery method. Smoking, vaping, and edibles can all have different effects, and their timing is covered below.

Cannabinoids can have biphasic effects, meaning a lower amount and a higher amount can act in opposite directions. The studies are small, and a physician should guide any medical use.

Two small trials found this pattern. In a 2017 randomized trial of 42 healthy adults, a lower oral THC dose eased stress during a public speaking task, while a higher dose worsened mood. Another example comes from a 2007 trial in 15 healthy volunteers: a medium dose of smoked cannabis reduced experimental pain, while a high dose increased it.

Dronabinol, a synthetic drug, is FDA-approved for chemotherapy nausea. A 2018 review NCCIH describes found a small benefit for some chronic pain. THC is also the compound behind the high. Some users report feeling more creative, elated or sleepy, though these are personal accounts, not trial results. But when the dosage of THC is too high, you might experience feelings of anxiety, paranoia, disorientation, hallucinations, and a heightened sensitivity to pain.

Does the Way You Take THC Change Its Effects?

The method of ingestion can also affect how quickly the effects of THC on the brain are felt and how long the effects last. Vaping and smoking cannabis deliver THC to the brain quickly, but smoke harms the lungs and NIH notes the FDA has warned against THC vaping products. The effects of inhaled THC also fade sooner.

THC in an edible or a drink takes longer to act, because it must pass through the digestive system first. While it can take 30 minutes to 2 hours for any of the effects to be felt, the effects last longer than the effects from smoking or vaping. CDC notes that many people who use edibles are caught off guard by their strength and long-lasting effects.

THC is one of the primary compounds found in the marijuana plant. The FDA has approved two prescription drugs that contain a synthetic form of it, dronabinol, but it can also have side effects that must be considered carefully. Before adding THC to your medical treatment, consult a doctor familiar with the drug about whether it fits your needs and how it may interact with your medicines.

Last updated October 16, 2026 by the Dr. Green Relief Editorial Team.

Sources

• NIDA. Cannabis (Marijuana)
• NCCIH. Cannabis (Marijuana) and Cannabinoids: What You Need To Know
• National Cancer Institute. Cannabis and Cannabinoids (PDQ), Health Professional Version
• FDA. FDA and Cannabis: Research and Drug Approval Process
• FDA. FDA Regulation of Cannabis and Cannabis-Derived Products, Including Cannabidiol (CBD)
• FDA. What You Need to Know (And What We’re Working to Find Out) About Products Containing Cannabis or Cannabis-derived Compounds, Including CBD
• CDC. Cannabis Health Effects
• CDC. Cannabis and Poisoning
• Howlett AC, et al. CB1 cannabinoid receptors and their associated proteins. Curr Med Chem. 2010 (PubMed)
• Childs E, et al. Dose-related effects of delta-9-THC on emotional responses to acute psychosocial stress. Drug Alcohol Depend. 2017 (PubMed)
• Wallace M, et al. Dose-dependent effects of smoked cannabis on capsaicin-induced pain and hyperalgesia in healthy volunteers. Anesthesiology. 2007 (PubMed)
• Public Law 119-103, section 2019 (govinfo)