Déjà vu is a fleeting, false memory — it can be harmless or a sign of something more

Déjà vu is a fleeting sensation of having already lived a totally identical situation at some point in the past — though, in reality, you haven’t. Translated from French, déjà vu means “already seen.”

An estimated 97% of people have experienced déjà vu at least once in their lives. Most of the time, it’s nothing more than a quick sensation that gives you pause for just a moment. Then, it’s back to normal.

But are there times when that momentary off-kilter feeling is trying to tell you something?

What is déjà vu?

“Déjà vu is a false sense of familiarity,” says neurologist Jean Khoury, MD. “Your brain creates a sensation as if you’ve been in a certain situation before, but you haven’t. So, you’re unable to retrieve it from your memory and can’t identify the actual situation.”

Maybe you know the feeling:

  • You’re in the midst of a conversation when, all of a sudden, you’re overwhelmed by the sensation that you’ve had this same talk before. You might even feel like you already know what the person is going to say.
  • You’re in line at the coffee shop and feel like you’ve seen this scene before. The other customers are standing just where you “remember” them.
  • You’re visiting a friend’s new place for the first time, but the layout, lighting or even a scent triggers a strong sense that you’ve been there before.

“There’s usually an incongruence between having this sense of familiarity but also knowing that the situation shouldn’t feel familiar,” Dr. Khoury notes.

What causes déjà vu to happen?

“Déjà vu is caused by dysfunctional connections between the parts of your brain that play a role in memory recollection and familiarity,” Dr. Khoury explains. “It’s a misfire that blurs the line between memory and new experience.”

In other words, it happens when there’s a miscommunication between two parts of your brain: The one responsible for memories (your temporal lobe) and the one responsible for taking in new information ( your hippocampus).

“If there’s a problem with how the hippocampus interacts with its surroundings, it can create a false memory that we experience as déjà vu. Memories and new experiences get wrapped up in each other,” he continues. “It’s a disruption of the recognition and memory systems that gives you that false sense of familiarity.”

Though researchers aren’t exactly sure why, some suggest you may be more susceptible to déjà vu if you:

  • Have a high level of education
  • Travel a lot
  • Remember your dreams

Health conditions and déjà vu

Some health conditions can cause déjà vu, including:

  • Fatigue or sleep deprivation: If you’re not getting enough sleep (or enough restful sleep), it can disrupt the recognition processes in your brain. That may also explain why people are often more likely to experience this phenomenon in the evenings.
  • Stress and anxiety: In times of stress, your brain can change how you perceive and process information. It’s a kind of coping mechanism to create some distance between what’s happening around you and how you’re experiencing it.
  • Migraines: People who are prone to migraines may find that they experience déjà vu either during the aura phase or during the migraine episode itself. Migraine pain can be disorienting and make it harder to process new information and recall memories.
  • Dementia: People who have frontotemporal dementia often experience persistent déjà vu and tend to try to rationalize the illusion.
  • Temporal lobe epilepsy and seizures: Not all seizures are what you see in the movies. “Seizures that are restricted to the temporal lobe can cause a misfire that creates the feeling of déjà vu, rather than shaking or other motor symptoms,” Dr. Khoury reports.

When to get help for déjà vu

Occasional déjà vu is nothing to worry about. But if you experience it often, or if it lasts longer than a few seconds or comes with other symptoms, it’s worth getting checked out.

“Déjà vu is an occasional phenomenon in healthy individuals, usually occurring a couple times a year,” Dr. Khoury confirms. “If it happens often enough to make you wonder, it’s worth talking to your provider.”

You should also tell a provider if your déjà vu episodes are accompanied by other potentially troubling symptoms, like:

  • Confusion
  • Headaches
  • Loss of awareness
  • Weakness
  • Seizures
  • Shaking

Bottom line? That occasional “been here, done this” experience probably isn’t anything to worry about. But don’t let persistent or worrisome déjà vu linger. If you have any doubts about the cause of your déjà vu, it’s important to consult with a healthcare provider or go straight to a neurologist.