marijuana and fatigue

Why Does Smoking Cannabis Make You Feel Tired?

Several studies could point towards a more complex link between cannabis and the feeling of tiredness experienced after smoking.

Every regular cannabis smoker has experienced drowsiness, lethargy, or a general lack of motivation after or while smoking weed. Many will shrug this off as the nature of a specific strain, while some may find these attributes desirable—especially if insomnia is an issue. Newly published research may point to excessive cannabis consumption as a cause of long-term feelings of drowsiness or laziness. For those choosing to use recreational cannabis to avoid the hangover or comedown of other drugs, this strategy may prove somewhat ineffective.


A strong indica strain will undoubtedly knock you down onto the sofa, where, let’s be honest, not a lot gets done. For a vast majority, this is a desirable trait, and the reason users choose indica strains to begin with. If you enjoy smoking cannabis and live an otherwise active lifestyle, then smoking will not suddenly make you lazy or lethargic for the long-haul. The answer to why marijuana makes us feel drowsy and in turn, less motivated, could actually come down to the way THC is absorbed and subsequently interacts with the neurotransmitter dopamine.


Published by The National Institute For Biotechnology Information, the following research points to an apparent reduction in dopamine levels as a result of excessive cannabis use. In summary, the study found that heavy smokers of cannabis, those who were borderline dependent, produced significantly less dopamine than that of non-smokers or light users.

Using a sample group of 19 frequent cannabis smokers and 19 non-smokers, this study stands out because, although similar tests have been undertaken before, none have included active smokers. Importantly, the frequent cannabis smokers had all admitted to suffering from psychotic-like symptoms when smoking, a sign of excessive use.

Michael Bloomfield, PhD stated that “After a period of time, your brain cells aren’t able to make as much tyrosine hydroxylase, an important enzyme that’s a key component in making dopamine”.

This stunting of chemical processes is a result of the way the cannabinoid THC interacts with our body’s natural endocannabinoid system.


With heavy THC consumption seemingly impacting dopamine levels, what does the release of dopamine mean to our bodies? Dopamine acts as a regulator for effort threshold—how much effort is required to complete a task and what the rewards are. Those with higher levels of dopamine are more likely to undertake functions that require energy. Dopamine also plays a role in giving us that “rewarding” feeling when taking part in pleasurable activities like sex, eating, and exercise. If the level of dopamine released during these activities is reduced, then it stands to reason that motivation to perform would also decrease.


Cannabis is a complex organism. Alongside key cannabinoids THC, CBD, and CBN, cannabis contains terpenes. These molecules provide the vast array of aromas we have come to love. More than that though, theorists suggest that terpenes work in unison with cannabinoids to boost or enhance the relative effect.

A 2011 study examined the impact of the terpene myrcene. Myrcene is known for giving cannabis a musky, mango-like aroma. Furthermore, myrcene was found to induce a hypnotic effect, as well as display muscle-relaxant properties. Combined with THC, these two compounds work in conjunction to make individuals feel tired. Previous studies have found similar attributes with the terpene linalool, although this time, linalool partnered with CBD to produce a drowsy effect.


Playing a potential role in reducing dopamine levels, what else can smokers expect THC to impact? Well, the answer may reside in the land of Nod. Anecdotal evidence from users would suggest we sleep better after smoking cannabis. Many have reported that we sleep so much better that the feeling of drowsiness can be hard to shake the morning after. With so many swearing by cannabis as a sleep aid, what scientific research is there to support this thesis?

Two studies, the first conducted in 1975 and more recently in 2004, delivered relatively inconclusive results. Both noted a decrease in REM sleep (rapid eye movement sleep phase), but our deep sleep phase remained roughly the same. It could be surmised that a reduction in REM sleep could result in the feeling of increased tiredness experienced the morning after smoking cannabis.

Both investigations have something in common—the vast number of variables yet to be explored. The results are still too inconclusive to draw a satisfactory conclusion. Instead, further studies will be needed, in which sample size, age of participants, strains smoked, and any previous medical issues, etc are taken into account. One thing is for sure; there does seem to be some correlation between smoking cannabis and the feeling of tiredness. The exact cause of this phenomenon is still unknown.


What does that mean for us? Well, for now, the usual rules apply. Enjoy cannabis as you usually would, while being aware that every user will experience symptoms differently. If you do find yourself having periods of drowsiness or lethargy the morning after smoking cannabis, then a few simple steps can be taken to counteract this.

These include selecting a strain with less THC, smoking less, and hydrating. And of course, exercise, a healthy diet, and good ole coffee can help shake the fatigue as well; be it a result of smoking weed or not.

Numerous users will have experienced drowsiness when smoking cannabis. Is this a natural reaction, or is there a long-term impact on our bodies?


Updated on January 25, 2019. Medical content reviewed by Dr. Joseph Rosado, MD, M.B.A, Chief Medical Officer

When you meet with your physician, they’re always considering whether the benefits outweigh the side effects of a medication, whether it’s a prescription drug or medical marijuana. While medical weed can cause side effects, like fatigue, its availability in different strains offers you and your doctor the opportunity to develop a treatment plan with minimal side effects.

Potential Side Effects of Medical Marijuana

While medical marijuana can cause unwanted side effects, like fatigue, it can also cause ones patients need. Those diagnosed with cancer and undergoing chemotherapy, for instance, may use medical weed as an appetite stimulant, which is also considered one of its potential side effects.

It’s crucial to note that your medical marijuana physician considers both the benefits and side effects of therapeutic cannabis before recommending it. If they feel it may cause you more discomfort, they won’t advise you to consider it as a treatment option. For them, it’s making sure your treatment plan offers you more pros than cons.

How Does Medical Weed Cause Fatigue?

Medical cannabis can cause both fatigue and drowsiness. With fatigue, you’re low on energy and motivation, whereas with drowsiness, you’re experiencing an intense need to sleep, which is one reason why those with insomnia use medical weed.

Fatigue from medical marijuana results from overuse, whether in a single dose or the long-term. One of marijuana’s primary cannabinoids, called tetrahydrocannabinol (THC), is thought by researchers to cause a lack of energy and motivation.

In the case of short-term overuse, your body has too much THC and is still processing it. With dependency, your brain’s dopaminergic neurons — which serve as transportation routes for dopamine, a chemical associated with your motivation and energy levels — become altered and decrease dopamine production. With less dopamine, you become fatigued.

Signs of Fatigue From Medical Cannabis

Symptoms of fatigue from medical cannabis often include:

  • Low motivation
  • Zero energy
  • Headaches
  • Slow responses or reflexes

Long-Term Side Effects of Fatigue

Experiencing fatigue for an extended period can lead to other issues, such as low performance at work and a decreased interest in your favorite hobbies. Being fatigued day-in and day-out takes a lot out of you, which is why it’s essential you speak with your medical cannabis physician if you’re experiencing chronic fatigue.

In some cases, it may not even be a side effect of your medical weed. Fatigue is also a primary symptom of several conditions, including anemia, fibromyalgia, diabetes and even thyroid issues. That’s why it’s vital to see a doctor when coping with fatigue.

How to Avoid and Manage Fatigue From Medical Marijuana

By working with your physician, as well as monitoring your dosage and intake of medical marijuana, you can prevent medical cannabis-induced fatigue. The most critical factor is taking a proactive approach and working with your doctor.

If you’ve started using medical weed and are now experiencing fatigue, it’s possible you’re consuming too much throughout the day. By adjusting your dosage plan with your physician, you can alleviate this side effect. If your doctor suspects your fatigue is the result of dependency, their primary goal will be to ensure your health.

Talk to Your Medical Marijuana Doctor About Your Fatigue Symptoms

Even though medical weed can cause fatigue, many patients still opt to use it under their medical marijuana doctor’s supervision. Quick changes to your treatment plan often make this symptom a non-issue, which is why it’s essential to have open, honest conversations with your medical cannabis doctor. With their help, you can customize your treatment plan to your needs.

Learn why some cannabis users experience fatigue as a side effect and how to combat side effects to get the most out of your cannabis.