What Is Déjà Vu?

Déjà vu is French for "already seen" and describes the sensation of recognizing a situation and thinking it's familiar—when it's not. It's difficult to pinpoint how many people experience it, but one study found that it affected about two-thirds of the population.

Déjà vu generally isn't good or bad—unless it happens often or with certain symptoms. Experiences of the sensation with symptoms like pale skin or increased heart rate could signal a potential case of a neurological disorder such as epilepsy. Here's what else you need to know about déjà vu.

What Causes Déjà?

Despite being fairly common, there's not much research about deja vu. Because it is a subjective experience and is difficult to induce in research subjects, testing the theories behind it can be tricky.

Some researchers believe déjà vu is triggered when you enter an environment similar to one you've experienced in the past. For example, you could experience it when you enter a hotel lobby where the furniture is configured like the living room of your childhood home.

To test this theory, researchers had participants go through virtual tours with similar layouts. When they moved through the scenes with a similar series of turns, participants felt like they had already "been there."

Some people who have temporal lobe epilepsy experience déjà vu right before they have a seizure. Temporal lobe epilepsy is a type of epilepsy that occurs in the part of the brain that handles short-term memory.

This could be argued to be another sign that the phenomenon is connected with memory activation in the temporal lobe. That's why some experts think déjà vu is triggered by a disruption in the firing of neurons in the brain.

Who Experiences It?

Déjà vu is more likely to happen to people between the ages of 15 and 25. There isn't much information about other risk factors beyond age. Despite this, travel, stress, and tiredness have been suggested as factors in experiencing this sensation.

When To See a Healthcare Provider

Having occasional—once or twice a year—déjà vu is a typical experience, even if scientists don't yet know exactly why it happens. In some cases, however, it may indicate a neurological disorder like epilepsy.

Talk to a healthcare provider if déjà vu is accompanied by symptoms such as:

• Feelings of fear or depersonalization—an out-of-body experience
• Flushing
• Impaired awareness
• Increased heart rate
• Olfactory hallucinations—smelling odors that aren't present
• Pale skin
• Vivid memories

A Quick Review

Déjà vu occurs when you recognize something to be familiar to you, even though you may not have experienced it. It tends to happen more often to individuals in their late teens to early 20s, but research about the phenomenon overall is limited.

Symptoms like flushing, smell-based hallucinations, and pale skin with déjà vu can indicate neurological problems. As long as you don't have these or other signs with those moments, déjà vu may only be your brain's way of processing memories.