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There are a lot of anecdotal reports of weed causing headaches but there is no clear answer as to why that happens. A lot of theories are floating around and we will take a look at the most likely causes but a lot more research into this field needs to undertaken before definite answers can be reached.

Poor Quality Marijuana

The legality of smoking weed is still in flux and it is banned in a lot more places than it is legal. This means that a large percentage of the population is getting its weed from sources that are dicey and the quality of the marijuana cannot be guaranteed.

The overuse of chemicals and fertilizers in growing the strains could lead to an increased amount of noxious gases being inhaled and resulting in a headache.

Some people also mix in weed with tobacco or are sold these mixtures without their knowledge which could again trigger headaches in their bodies.

Increased Blood Flow To The brain

There are studies which have investigated the change in cerebral blood flow after smoking marijuana and found that certain regions of the brain did see an increase in blood flow. This increased amount of dilatation and thus increased pressure could cause a headache in some individuals.

The drawback with this theory is that the same sort of physiological effect should be seen in most individuals and so a lot more people should be complaining about a headache.

The theory of increased regional cerebral blood flow could be much more useful in explaining the cognitive effects of marijuana smoking than headaches in our opinion.

Dopamine Release

Marijuana causes a release of dopamine by the brain and this is another reason for the mood uplifting and mood-altering effects that are observed. According to this theory, the brain actually starts to become a lot more stimulated under the effects of dopamine and becomes hyperactive causing it to be strained.

As the effects of the dopamine start to wear away, the brain starts to come back to a normal function and is stressed due to the overactivity it has been put through, resulting in a headache.

Allergic reaction

While it is certainly possible that some people suffer from headaches after smoking poor-quality marijuana, what about those people that buy their weed from licensed stores legally? Ideally, these stores should only be selling weed that has been checked for contaminants.

One of the possible causes of a headache could be an allergic reaction to the cannabinoid contents. Try and change the strain of marijuana to see if that helps or try taking a break for some weeks to let any contaminants in your system be flushed away.


Cannabis has been found to be useful in treating tension headaches in humans and there is currently no scientific evidence that says it actually causes headaches. This, however, could be because of a lack of research rather than any other reason.

In the meantime, it is better to make sure your weed is being Procured legally through licensed stores to minimize the chances of contamination since that seems the most likely culprit behind complaints of headaches.

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