Does Smoking Weed Stunt Muscle Growth?

Cannabis does not appear to directly stunt muscle growth in any straightforward way, but the full picture is messier than a simple yes or no. THC interacts with receptors found on skeletal muscle cells, can temporarily shift hormone levels, and alters how your body handles stress and recovery. None of these effects have been shown in human studies to meaningfully block hypertrophy in people who train consistently, though some of the underlying biology raises legitimate concerns worth understanding.

Your Muscles Have Cannabinoid Receptors

The reason cannabis has any relevance to muscle growth at all is that your skeletal muscles contain CB1 cannabinoid receptors, the same type of receptor THC primarily acts on in your brain. These receptors sit mostly on cell membranes, though a subset lives on mitochondria, the energy-producing structures inside muscle cells.¹ The endocannabinoid system as a whole influences processes relevant to muscle, including protein balance, insulin sensitivity, mitochondrial metabolism, and muscle development.²

What this means practically is that when you consume THC, it does not just affect your brain. It binds to receptors throughout your musculature, at least in theory influencing how those muscles grow, repair, and use energy. The question is whether normal recreational use produces enough of an effect at those receptors to actually interfere with gains.

What Happens to mTOR and Growth Signaling

mTOR is a key molecular switch that tells your cells to build protein, and it is central to the process of muscle growth after training. In mice treated with THC over several weeks, researchers found that mTOR activity was temporarily increased at the two-week mark, with phosphorylation levels rising by about 47% in brain tissue compared to controls.³ That might sound like good news for muscle building, but the study showed this was a temporary shift that changed direction with continued exposure, and the work measured brain tissue rather than skeletal muscle. Still, it illustrates that THC does not simply suppress growth pathways in a one-dimensional way.

Meanwhile, preclinical research on blocking the CB1 receptor paints a more telling picture. When researchers used drugs or genetic tools to shut down CB1 signaling, the result was enhanced muscle growth through pathways including the very same mTOR system, along with improved insulin sensitivity and better mitochondrial function.⁴ The implication is that activating CB1 receptors, which is what THC does, could theoretically push things in the opposite direction. But “theoretically” is doing a lot of heavy lifting here. These are animal studies using receptor-blocking drugs, not measurements of what happens in a person who smokes a joint after a workout.

The Testosterone Question

One of the most persistent fears around cannabis and muscle is that it tanks testosterone. The data on this is surprisingly reassuring. A large study using nationally representative data from American men found no difference in serum testosterone between those who had ever used marijuana and those who had never used it, after adjusting for confounders.⁵ The average adjusted testosterone was virtually identical between the two groups.

The more nuanced finding was about timing rather than lifetime use. Recency of use, not how long someone had been smoking or how often, had the strongest relationship with testosterone. Among men aged 18 to 29, those who had used more recently tended to have slightly higher testosterone levels.⁵ This was an inverse association with time since last use, meaning the further out someone was from their last session, the lower the levels trended. Researchers have speculated this might relate to acute hormonal responses rather than any permanent shift. Either way, the popular claim that weed “kills your T levels” does not hold up in the population-level data.

Cortisol, Stress, and the Recovery Window

Cortisol is the other hormone people worry about. It is catabolic, meaning it promotes tissue breakdown rather than building, and chronically elevated cortisol works against muscle growth. Acute cannabis exposure does raise cortisol, sometimes substantially.⁶ Getting high triggers a measurable stress-hormone spike.

Chronic use, however, seems to flip this pattern. Regular cannabis users tend to show a blunted cortisol awakening response and a flatter cortisol curve throughout the day.⁶ A study of frequent users confirmed that while their morning cortisol was higher than non-users, their overall stress reactivity was dampened.⁷ Whether a flattened cortisol rhythm is good or bad for muscle depends on context. A chronically elevated baseline is harmful, but a blunted response to training might also mean your body is less responsive to the stress signal that drives adaptation. The honest answer is that nobody has directly measured whether these cortisol changes translate into different muscle growth outcomes in people who lift.

CBD and Muscle Recovery

CBD, the non-intoxicating compound in cannabis, has attracted separate interest for muscle recovery. In rodent studies, CBD reduced inflammation markers in muscle after eccentric exercise and in models of muscular dystrophy and obesity. There are also some human indications that CBD supplementation improved markers of recovery and even squat performance.⁸ One human trial found that oral CBD supplementation reduced markers of muscle damage, specifically creatine kinase and myoglobin, at the 72-hour mark after intensive resistance training, though the effect was not apparent at 24 or 48 hours.⁹

Before you start rubbing CBD cream on your biceps, though, a separate study testing topical CBD ointment on delayed-onset muscle soreness found no benefit at all. Arm swelling, strength loss, and soreness were all statistically identical between the CBD arm and the placebo arm.¹⁰ The delivery method seems to matter. Oral CBD reaching the bloodstream is a fundamentally different thing from a cream sitting on the skin over a sore muscle. Anyone spending money on topical CBD products for gym recovery should know the evidence so far says they do not work for that purpose.

It is also worth keeping CBD conceptually separate from THC and whole-plant cannabis. A person asking whether “smoking weed” hurts their gains is mostly asking about THC. CBD is a different compound with different receptor activity, and the recovery benefits observed in some studies do not transfer to conclusions about getting high.

Exercise Performance Under the Influence

Training quality matters enormously for muscle growth, and this is where cannabis use may have its most practical impact. A review in Sports Medicine concluded that studies of whole cannabis and THC have generally shown either no effect or a negative effect on exercise performance in both strength and aerobic activities.¹¹ That said, the researchers noted the studies that exist are not rigorous enough to make a definitive call in either direction.

Cardiovascular responses during exercise paint a similar picture of mild disruption. Research on acute cannabis use and cycling performance found that while blood pressure during maximal effort was unchanged by cannabis, THC-predominant cannabis elevated pulse pressure after exercise and altered a measure of cardiac systolic function in the post-exercise period.¹² During the actual exercise, though, cardiac function and blood pressure were not measurably different. The concern here is less about muscle growth directly and more about training while high: if THC reduces your coordination, focus, or willingness to push through hard sets, you will train less effectively, and that subpar training is what could limit your progress over time.

The Body Composition Paradox

One of the more puzzling findings in this area is that cannabis users tend to be leaner than non-users, despite THC’s well-documented ability to increase appetite and food cravings. A review of available data found that the average BMI of cannabis users was about 26, compared to 27.5 for non-users. Among the heaviest users, the average BMI dropped further to about 25.5, putting them near the boundary of the healthy range.¹³ The effect size was large and the difference clinically meaningful.

This paradox persists across studies. A more recent review confirmed that despite cannabis being associated with increased appetite, overconsumption, and decreased physical activity, most evidence suggests it is not associated with weight gain, and may even facilitate weight loss.¹⁴ Nobody fully understands why. The leading theories involve changes in gut microbiome signaling, metabolic rate adjustments, or the downregulation of CB1 receptors with chronic use, which as discussed above would push metabolism in the same direction as the CB1-blocking drugs that promote leanness in animal studies.

For someone worried about body composition, this data is counterintuitive but consistent. Cannabis users are not, on average, getting fatter. Whether the munchies might cause you to under-eat protein or over-eat junk food on a given evening is a separate, more personal question that depends on your habits rather than on pharmacology.

Neuromuscular Effects

Beyond muscle tissue itself, cannabinoids affect the nerve signals that control your muscles. A systematic review of how cannabinoids influence motor neuron output found that activating CB1 receptors at motor neuron synapses generally promoted excitation by enhancing excitatory signals and suppressing inhibitory ones.¹⁵ CB1 activation also increased the frequency of cyclical motor patterns. However, the effects on acetylcholine release at the neuromuscular junction, the actual chemical handoff that makes a muscle fiber contract, were inconsistent across studies. Some showed enhancement, some showed suppression, and the reviewers concluded more work is needed to sort it out.

In practical terms, this might partly explain why some people feel their mind-muscle connection changes when high. The subjective experience of altered body awareness during cannabis use likely reflects real changes in how motor circuits are firing, though whether this helps or hurts a workout depends on the task and the individual.

Sex Differences in How Cannabis Affects Muscle

Men and women respond differently to cannabinoids, and some of that difference traces directly to body composition. Because THC is fat-soluble, it distributes and persists differently depending on the ratio of muscle mass to fat tissue, which varies significantly between sexes.¹⁶ Women on average have higher body fat percentages, which means THC may accumulate more and be released from fat stores over a longer period. Hormonal interactions with estrogen and progesterone further modify how cannabinoids are metabolized and how strongly they bind to receptors. If research ever does identify a meaningful effect of THC on muscle growth, it would almost certainly differ between men and women, and studies that pool both sexes without accounting for this could easily miss or understate real effects in one group.

When Cannabinoids Actually Protect Muscle

In a twist that complicates the “weed kills gains” narrative, cannabinoids have shown genuine protective effects against muscle wasting in disease contexts. In a mouse model of colorectal cancer, treatment with THC and CB2 receptor activation reduced the skeletal muscle atrophy that typically accompanies the disease. The mechanism involved modulating immune cell infiltration into muscle tissue.⁸ This is obviously not the same as recreational cannabis use in a healthy person trying to build muscle, but it demonstrates that cannabinoids are not simply anti-muscle compounds. In the right context, they actively preserve muscle mass.

Separately, hemp seed extract, which comes from the same plant but contains negligible THC, has been shown to promote muscle cell proliferation in lab cultures by stimulating growth factor signaling, specifically IGF-1 production through the JAK2/STAT5b pathway.¹⁷ Hemp seeds are a legitimate protein source used in some fitness nutrition, and their growth-promoting effects operate through completely different mechanisms than THC. Conflating hemp foods with smoking cannabis would be a mistake in either direction.

What Probably Matters More Than the Pharmacology

The gap between cellular-level findings and real-world muscle outcomes is enormous. Your muscles grow because you train with progressive overload, eat enough protein and calories, sleep adequately, and stay consistent over months and years. Cannabis intersects with several of these factors indirectly. If smoking before bed disrupts your deep sleep architecture, that could impair overnight recovery and hormone secretion. If getting high makes you skip the gym, eat poorly, or train half-heartedly, the cumulative effect on your physique will be far larger than any receptor-level interaction.

The Sports Medicine review’s conclusion is probably the most honest framing available: studies have generally shown null or slightly negative effects on performance, but the research quality is not strong enough to make definitive claims.¹¹ Nobody has run a long-term, well-controlled trial comparing muscle hypertrophy in cannabis users versus non-users who follow the same training and nutrition program. Until that study exists, the best available answer is that cannabis is unlikely to be a major direct obstacle to muscle growth for most people, but the behavioral and lifestyle effects around its use, from training motivation to sleep quality to dietary choices, are where the real risks to your gains probably live.

Smoking Versus Other Delivery Methods

How you consume cannabis adds another layer. Smoking anything, whether cannabis, tobacco, or anything else, introduces carbon monoxide and combustion byproducts into your bloodstream. Carbon monoxide binds to hemoglobin far more readily than oxygen does, temporarily reducing your blood’s oxygen-carrying capacity. For someone doing high-intensity training, this means less oxygen reaching working muscles during and after a session. Chronic smoking also causes airway inflammation that can limit aerobic capacity over time.

Vaporizing, edibles, and tinctures avoid combustion entirely. The cardiovascular study mentioned earlier included both smoked and vaporized THC conditions and found that smoked THC produced more pronounced changes in post-exercise cardiac function than vaporized THC.¹² If you are going to use cannabis and care about training performance, the delivery method is a variable you can control. Edibles and vaporizers eliminate the respiratory burden, though they come with their own considerations around dosing precision and onset timing.

1
PubMed Central. Genetic Manipulation of CB1 Cannabinoid Receptors Reveals a Role in Maintaining Proper Skeletal Muscle Morphology and Function in Mice
2
PubMed Central. Endocannabinoid system and skeletal muscle health: Insights from cannabidiol
3
ACS Pharmacology & Translational Science. Bidirectional Effect of Long-Term Δ9‑Tetrahydrocannabinol Treatment on mTOR Activity and Metabolome
4
PubMed. Impact of CB1 receptor antagonism on skeletal muscle hypertrophy and metabolic health: a systematic review of preclinical studies
5
PubMed Central. Marijuana use and serum testosterone concentrations among U.S. males
6
PubMed Central. A review of the effects of acute and chronic cannabinoid exposure on the stress response
7
Cannabis. Subjective Stress and Diurnal Salivary Cortisol in Adults with Frequent Cannabis Use
8
Biomedicine & Pharmacotherapy. The protective effect of cannabinoids against colorectal cancer cachexia through modulation of inflammation and immune responses
9
PubMed Central. Effects of Cannabidiol Supplementation on Skeletal Muscle Regeneration after Intensive Resistance Training
10
PubMed Central. Topical Cannabidiol and the Progression Rate of Delayed Onset Muscle Soreness
11
PubMed Central. Cannabis and Athletic Performance
12
PubMed. The acute cardiovascular response to dynamic exercise and recovery following cannabis use
13
PubMed Central. Theoretical Explanation for Reduced Body Mass Index and Obesity Rates in Cannabis Users
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PubMed Central. Cannabis, Weight, and Weight-Related Behaviors
15
PubMed Central. A systematic review of how cannabinoids affect motoneuron output
16
PubMed Central. How important are sex differences in cannabinoid action?
17
PubMed Central. Hemp seed extract as a catalyst for cell proliferation via IGF-1 and growth hormone signaling