Marijuana is not technically an anticholinergic drug, but it produces several effects that look and feel anticholinergic. THC, the primary active compound in cannabis, does not directly block acetylcholine receptors the way classic anticholinergic drugs do. Instead, it activates cannabinoid (CB1) receptors, which in turn reduce acetylcholine release in certain parts of the body. The result is a set of overlapping symptoms: dry mouth, increased heart rate, and short-term memory problems.
How THC Affects Acetylcholine Indirectly
Classic anticholinergic drugs like diphenhydramine or atropine work by physically blocking muscarinic acetylcholine receptors. THC takes a different route. It binds to CB1 receptors, which are located on the surface of nerve cells that release acetylcholine. When THC activates those CB1 receptors, the nerve cells release less acetylcholine. The end result is similar (less acetylcholine signaling), but the mechanism is upstream of the receptor rather than at the receptor itself.
Research on the hippocampus, a brain region critical for memory, shows that cannabinoids have a biphasic effect on acetylcholine. Depending on the dose and the specific brain circuits involved, THC can either reduce or increase acetylcholine release. Both effects operate through CB1 receptors coupled to the same type of signaling protein, but they involve different anatomical pathways. In practical terms, the net effect at typical recreational or medicinal doses tends to suppress acetylcholine activity in ways that matter for memory and certain body functions.
Why Cannabis Causes Dry Mouth
Dry mouth is one of the most common side effects of cannabis use, and it’s also a hallmark of anticholinergic drugs. For years, the mechanism behind cannabis-induced dry mouth was unclear. Recent research published in Scientific Reports has filled in the picture: CB1 receptors sit on the cholinergic nerve fibers that control the submandibular gland, one of the major saliva-producing glands.
When THC activates those CB1 receptors, it reduces acetylcholine release from the nerves supplying the gland. Less acetylcholine means less saliva production. Importantly, THC does not block the acetylcholine receptors on the gland itself. If you apply acetylcholine or a drug like pilocarpine directly to the salivary gland tissue, it still responds normally. This confirms that THC is reducing the signal rather than blocking the receiver, a key distinction from true anticholinergic action.
Heart Rate Effects
Tachycardia, or a noticeably faster heart rate, is another effect cannabis shares with anticholinergic drugs. Smoking marijuana causes an immediate increase in heart rate and elevated blood pressure. In one study, a CB1-selective blocker reduced the peak heart rate increase by 59% in healthy volunteers, confirming that CB1 activation drives most of the effect.
The mechanism appears to involve multiple pathways. Cannabis enhances sympathetic nervous system activity (the “fight or flight” side), which speeds the heart. It also inhibits parasympathetic input to the heart, reducing the vagal tone that normally acts as a brake on heart rate. This parasympathetic suppression is the part that most closely resembles anticholinergic action, since the vagus nerve uses acetylcholine as its signaling molecule. On top of these, THC-induced blood vessel dilation triggers a reflex increase in heart rate.
The cardiovascular picture is dose-dependent. Lower doses tend to stimulate the sympathetic system and raise heart rate, while higher doses can paradoxically slow the heart and lower blood pressure through parasympathetic activation. This biphasic pattern mirrors what researchers see in the brain with acetylcholine release.
Memory Impairment: Similar Outcome, Different Path
Both cannabis and anticholinergic drugs impair short-term and working memory, which is one reason people wonder whether they share a mechanism. Cannabis-induced memory problems are primarily driven by CB1 receptor activation in the hippocampus, not by direct blockade of acetylcholine receptors. The downstream effects likely involve reduced brain glucose availability and shifts in neurotransmitter levels, including but not limited to acetylcholine.
Animal research highlights an important interaction between the two. When mice were given both cannabis and scopolamine (a classic anticholinergic), their memory performance was significantly worse than with scopolamine alone. They took longer to complete memory tasks, suggesting that the two substances compound each other’s cognitive effects even though they work through different receptor systems. This additive impairment is worth keeping in mind if you use cannabis alongside any medication with anticholinergic properties.
Not Listed as an Anticholinergic Drug
Clinical tools like the Anticholinergic Cognitive Burden (ACB) scale, which pharmacists and physicians use to assess how much anticholinergic load a patient carries from their medications, do not include cannabis or THC. This is because THC does not bind directly to muscarinic acetylcholine receptors with meaningful affinity. Its effects on the cholinergic system are indirect, mediated entirely through the endocannabinoid system.
From a pharmacological standpoint, calling marijuana “anticholinergic” would be imprecise. A more accurate description is that it has anticholinergic-like effects through CB1-mediated suppression of acetylcholine release.
Risks When Combined With Anticholinergic Medications
Even though cannabis works through a different mechanism, combining it with true anticholinergic medications can amplify side effects. Tachycardia is a specific concern when cannabis is used alongside first-generation antihistamines (like diphenhydramine) or tricyclic antidepressants, both of which have strong anticholinergic properties. The sedation, slowed reaction time, and concentration difficulties caused by THC are also additive with other central nervous system depressants, including sedating antihistamines.
Older adults are particularly vulnerable to these compounding effects, since they are more likely to take multiple medications with anticholinergic activity and are more sensitive to cognitive side effects. If you take any medication that lists dry mouth, constipation, or blurred vision among its side effects, those are markers of anticholinergic activity, and cannabis could make each of them more pronounced.