Deja vu

Déjà vu is a compelling sense that a current moment has already been experienced, despite knowing it has not.

As a drug effect it is acute and dose-dependent, easing as the substance wears off — distinguishing it from the persistent déjà vu of certain neurological conditions. It ranges from a fleeting impression of uncanny familiarity to a sustained conviction that the present is a repetition of the past.

It is an uncommon effect across the substances that can produce it. It is most commonly induced at moderate to high doses under psychedelics such as LSD, psilocybin mushrooms, and DMT, and under dissociatives such as ketamine, dextromethorphan, and 2-fluorodeschloroketamine. It also appears at lower doses under depressants such as zolpidem.

Déjà vu is felt as an uncanny doubling of the present: the scene, conversation, or moment seems simultaneously new and already known, producing a mild cognitive vertigo that resists rational correction.

It commonly comes with a brief suspension of forward-moving attention as the mind loops back, searching for the remembered original. Attending to the feeling tends to prolong it — the effort to resolve the mismatch deepens the sense of repetition. At higher doses under psychedelics and dissociatives, it can extend into sustained loops that blur past and present.

Déjà vu arises through different pathways depending on the drug class:

• Psychedelics — act on 5-HT2A receptors, altering the timing of memory encoding and retrieval; an ongoing moment may be tagged as already-stored before it is fully processed.
• Dissociatives — block NMDA receptors, disrupting the normal sequencing of perception and memory formation and producing fragments of familiarity decoupled from their source.
• Depressants — zolpidem in particular is associated with transient memory anomalies at sleep onset that can present as déjà vu.

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 duration. It is more likely in sleep-deprived states and during periods of dissociated attention — especially under psychedelics and dissociatives — and in people with a prior history of spontaneous déjà vu.

Expectation plays a role: entering an experience already primed for unusual temporal perception makes it more likely to appear. Grounded, calm attention and familiarity with a substance tend to reduce its frequency.