Odds are, you've experienced déjà vu at some point in your life. The sensation can feel unnerving, mysterious, and even a bit mystical—but what does it really mean? To find out, we asked an expert and dug into the research. Here's what to know.
What is déjà vu?
Déjà vu is a sense that your current experience has happened before, registered clinical counselor Leslie Ellis, Ph.D., tells mbg. The term itself is French for "already seen," which succinctly describes exactly what déjà vu is all about.
One 1992 study on déjà vu defines it as "a dissociative phenomenon which can be characterized as a subjectively inappropriate impression of familiarity of the present with an undefined past."
It may happen when you see a scene that looks eerily familiar or hear a friend say something that you swear they've said before. What makes the experience of déjà vu so unnerving is that people usually can't place exactly why the scene feels familiar or when it originally happened.
Who experiences déjà vu?
According to Ellis, almost everyone experiences déjà vu sometimes, with roughly two-thirds (60 to 70%) of people experiencing it "fairly regularly."
It's thought to happen less as we get older and appears to be associated with stress and fatigue. The phenomenon is particularly common among people with temporal-lobe epilepsy and some other psychiatric conditions, according to research on epileptic patients—with virtually all people with epilepsy having experienced déjà vu. Interestingly, the sensation often happens right before a seizure, which is known as "ictal déjà vu." Other research has also linked it with dementia.
"Temporal lobe epilepsy, migraines, anxiety, and dissociation can be associated with more frequent and extended déjà vu experiences," Ellis notes, adding, "Neurobiologists suggest it could be explained by parts of our brain being out of sync, and they have been able to induce déjà vu in the lab by stimulating specific cortical structures."
All that to say, déjà vu is common, and while it can be related to certain conditions, it is not a cause for alarm. "Déjà vu can warn of epilepsy or other neurological issues, but in most cases, it is a benign and mysterious experience to wonder about and enjoy," Ellis says.
With that being said, if you're experiencing a seemingly high or bothersome amount of déjà vu experiences, talk to your doctor.
What it's caused by.
As Ellis explains, "Neuroscientists have identified the temporal region as the location in the brain responsible for the experience of déjà vu but not the reason behind it." There has been extensive research on the topic, though she adds the actual cause of it remains a mystery.
That said, one 2010 study on déjà vu published in the journal Psychology of Motivation and Learning identified three potential mechanisms that could trigger it:
In a split perception scenario, déjà vu is caused by "a brief glance at an object or scene just prior to a fully aware look." When this happens, your perception is "split into two parts and appears to be eerily duplicated," the study authors explain.
Implicit memory involves a previous setting that someone has indeed experienced before, but the scene was "stored in such an indistinct manner that only the sense of familiarity is resurrected."
This can also happen when one part of a larger scene seems familiar, but you can't place why, "with the result that the strong sense of familiarity associated with this portion inappropriately bleeds over onto the entire scene," the study authors say.
Lastly, gestalt familiarity involves a present setting "closely resembling something experienced before in outline but not in specifics." This is almost like the reverse of implicit memory, where rather than one part of a larger scene feeling familiar, the larger scene feels familiar even if the specifics do not.
Why does déjà vu happen?
While the jury may still be out on the exact neurological, psychological, and/or pathological cause of déjà vu, there are some spiritual theories as to why it happens.
Déjà vu has also been associated with precognitive dreaming (aka dreams that seemingly predict the future) and déjà rêvé, which translates to "already dreamed" and describes the sensation that you've dreamed about something before it happened in real life.
Ellis adds that from a spiritual perspective, déjà vu is considered to be linked to transcendence. Spiritual author Shannon Kaiser previously told mbg something similar, explaining that frequent synchronicities, including déjà vu, can be a sign of a spiritual awakening.
The bottom line.
While déjà vu remains somewhat of a mystery, it's typically not a cause for alarm, and rather an extraordinary (and maybe slightly creepy) phenomenon. Until we have all the answers on what's really going on when we feel that uncanny sense of familiarity, allow the experience of déjà vu to help you foster curiosity and wonder.
Sarah Regan is a Spirituality & Relationships Writer, as well as a registered yoga instructor. She received her bachelor's in broadcasting and mass communication from SUNY Oswego, and lives in Buffalo, New York.