Bruxism

Bruxism is the involuntary clenching of the jaw and grinding of the teeth.

As a drug effect it is acute and dose-proportional, easing as the substance wears off, which sets it apart from chronic bruxism arising from sleep disorders or habitual tension. It ranges from a subtle jaw tightness to sustained, forceful grinding that can produce soreness, headache, and cumulative tooth damage.

It is among the most reliably reported physical adverse effects of stimulants. It is most commonly induced at moderate to high doses under stimulants such as amphetamine, MDMA, and cocaine, and under psychedelics such as LSD and MDA; it also appears under nootropics such as 5-hydroxytryptophan and meclofenoxate, and occasionally under deliriants such as diphenhydramine.

Bruxism is felt as a persistent, involuntary urge to clench: the jaw muscles tighten, the teeth press together with more force than intended, and the jaw may shift sideways or forward.

It commonly comes with aching at the jaw hinge, facial tension radiating toward the temples, and a dull pressure behind the eyes. Attempting to relax the jaw typically brings only brief relief before the clenching reasserts itself.

At higher doses, particularly under stimulants, the grinding can become rhythmic and nearly continuous, deepening the muscular soreness with each passing hour.

Bruxism arises through different pathways depending on the drug class:

• Stimulants — elevate dopamine and norepinephrine, increasing muscular tension throughout the body including the masticatory muscles; MDMA additionally raises serotonin, producing a particularly pronounced clenching response.
• Psychedelics — act on 5-HT2A receptors and heighten general motor restlessness, which can manifest as jaw tension and clenching.
• Nootropics — serotonergic agents such as 5-hydroxytryptophan may modulate jaw motor tone through serotonin pathways.
• Deliriants — can produce involuntary muscle activity through anticholinergic mechanisms.

How much each pathway contributes in a given case is not fully understood.

Who experiences it, and how strongly, varies widely. Higher doses raise both its likelihood and intensity. Preexisting jaw tension, teeth-clenching habits, or temporomandibular joint sensitivity significantly amplify it — especially under stimulants and serotonergic psychedelics. Individual sensitivity to dopaminergic and serotonergic activity shapes how pronounced it becomes.

Going in with body awareness tends to make the clenching more noticeable once it starts. A soft mouthguard substantially reduces dental and muscular impact even when the clenching itself persists.