Cannabis affects nearly every major system in your body, from your brain and heart to your lungs and digestive tract. The primary psychoactive compound, THC, works by hijacking a signaling network your body already uses to regulate mood, pain, appetite, and memory. Today’s cannabis is also significantly stronger than what was available a generation ago, with average THC concentrations in seized samples reaching about 16% in 2022, roughly four times higher than levels measured in the mid-1990s.
How THC Interacts With Your Brain
Your body has its own cannabis-like signaling system called the endocannabinoid system. It uses naturally produced molecules that bind to two main types of receptors: CB1 receptors, concentrated heavily in the brain, and CB2 receptors, found mostly in immune cells, the spleen, and bone tissue. THC mimics your body’s own signaling molecules and activates CB1 receptors throughout the brain, which is what produces the high.
One of the most important things THC does is boost dopamine activity in your brain’s reward pathway. This is the same circuit activated by food, sex, and every other known drug of abuse. THC increases the firing rate of dopamine-producing neurons, flooding a key reward center with dopamine. This creates the pleasurable, reinforcing feeling that makes people want to use cannabis again. Repeated exposure can cause lasting changes in how this reward system functions, which is part of how dependency develops.
The High: Onset and Duration
How you consume cannabis dramatically changes what you experience and when. Smoking or vaping delivers THC from the lungs to the brain almost instantly, with effects typically peaking within minutes. Edibles take a completely different route through your digestive system, delaying onset by 30 to 90 minutes. Blood levels of THC after eating cannabis tend to start peaking around the 60-minute mark on average.
This delay is why edibles catch people off guard. You feel nothing for half an hour or more, eat more thinking the first dose didn’t work, and then the full combined dose hits at once. The effects of edibles also last considerably longer than smoking, often several hours, because THC is absorbed and metabolized more slowly through the gut and liver.
Effects on Your Heart
THC causes an acute, dose-dependent spike in both heart rate and blood pressure. The more you consume, the more pronounced the cardiovascular response. For most young, healthy people, this temporary increase is manageable. But for anyone with an underlying heart condition, the added strain on the cardiovascular system poses real risk. This is one reason cannabis-related emergency room visits sometimes involve chest pain or heart palpitations, particularly in people who aren’t aware of a pre-existing issue.
Why Cannabis Makes You Hungry
The “munchies” are a real physiological event, not just a stereotype. Cannabis has well-documented appetite-stimulating properties that work through multiple pathways. One involves ghrelin, often called the hunger hormone, a peptide produced in your gut that tells your brain it’s time to eat. Ghrelin receptors and cannabinoid receptors can form paired units in the brain’s reward circuits, and when both are activated simultaneously, the combined signal is stronger than either one alone. This amplified signaling likely explains why food doesn’t just sound good when you’re high; it feels intensely rewarding.
Interestingly, the relationship between THC dose and hunger isn’t linear. Lower doses tend to increase appetite, while very high doses can actually suppress it. The endocannabinoid system also appears to specifically influence the hedonic side of eating, the pleasure you get from food, rather than just caloric need. This is why cannabis tends to make you crave rich, flavorful foods rather than simply making you feel empty.
Memory and Cognitive Effects
One of the most consistent short-term effects of cannabis is impaired memory. THC interferes with your ability to form new memories by acting on CB1 receptors in the hippocampus, a brain region critical for encoding experiences into lasting memory. This is why you might struggle to remember conversations or lose your train of thought while high. Most of these effects are temporary and clear as THC leaves your system.
CBD, the other major compound in cannabis, actually exerts opposing effects to THC in the hippocampus and other receptor-dense brain regions. Products with higher CBD-to-THC ratios may partially buffer against some of THC’s cognitive downsides, though THC still dominates the experience in most commercial cannabis.
What Smoking Does to Your Lungs
Cannabis smoke contains many of the same toxins, irritants, and carcinogens found in tobacco smoke. According to the CDC, smoked cannabis can harm lung tissue and cause scarring and damage to small blood vessels regardless of how it’s smoked, whether through a joint, pipe, or water pipe. Regular smoking increases the risk of bronchitis, chronic cough, and excess mucus production.
The good news is that these respiratory symptoms generally improve after quitting. Unlike some tobacco-related lung damage, the airway irritation from cannabis smoke appears to be largely reversible once exposure stops. Vaping, edibles, and other non-combustion methods avoid most of these lung-specific harms, though each comes with its own considerations.
Risks for Adolescent Brains
The developing brain is particularly vulnerable to cannabis. Adolescents with histories of heavy use perform measurably worse on tests of flexible thinking, impulse control, and sustained attention compared to peers who don’t use. Those who start before age 15 show the most pronounced deficits in executive functioning, the set of mental skills that govern planning, decision-making, and self-regulation.
Brain imaging studies reveal structural differences as well. Adolescent cannabis users show reduced volume in the medial orbital prefrontal cortex, a region essential for judgment and impulse control, with younger age of first use linked to greater reduction. Other studies have found unusual volume changes in the cerebellum, a region involved in coordination and cognition, with larger cerebellar volume paradoxically associated with poorer executive function. These findings suggest cannabis doesn’t just temporarily impair a developing brain but may alter its architecture during a critical window of growth.
Dependency and Cannabis Use Disorder
Cannabis can be habit-forming. About 2.5% of American adults meet the criteria for cannabis use disorder in any given year, and roughly 6.3% develop it at some point in their lifetime, based on a large national epidemiological survey. The disorder is diagnosed when someone experiences two or more of eleven possible problems within a 12-month period, including cravings, withdrawal symptoms, using more than intended, and continued use despite negative consequences. Severity ranges from mild (two to three criteria) to severe (six or more).
Among people who do develop the disorder, use tends to be frequent. The average was about 225 days per year for those with a current diagnosis and 274 days per year for those with a lifetime history. Withdrawal symptoms, which were formally recognized as a diagnostic criterion in 2013, can include irritability, sleep difficulties, decreased appetite, and restlessness. They’re not dangerous, but they’re uncomfortable enough to keep many people using.
The repeated dopamine surges from regular use are part of what drives dependency. Over time, the brain’s reward circuitry adapts to the presence of THC, requiring more to achieve the same effect and leaving baseline mood and motivation feeling flat without it. This process, called neuroadaptation, affects not just the dopamine pathway itself but downstream brain systems involved in motivation and habit formation.