Why Do People Experience Déjà Vu?

If you’ve ever thought, “I’ve done or seen this before,” in the middle of a new experience, it might have been the neurological phenomenon known as déjà vu. While it’s fairly common, it occurs in some people more than others—and although it’s typically harmless, frequent experiences of it are associated with some neurological conditions.

What does déjà vu feel like?

This term is French for “already seen.” The dictionary definition is “a feeling of having already experienced the present situation.” Usually very brief and fleeting, this odd sense can feel unsettling and inexplicable because your brain is telling you that you recognize a place, scene, or event that you know is brand-new to you. It’s not just a feeling of familiarity, but also the knowledge that the familiarity is false.

It typically occurs on an irregular basis, but déjà vu can leave some with such a strange sensation that they remember it for months or years. The sudden feeling of familiarity during déjà vu could be linked to nerve cell activity in a healthy brain, as the brain processes new information and tries to connect it to existing memories.

It’s also been found to happen more frequently in those between the ages of 15 and 25, with the frequency of the experience tapering off with age. While all aspects of this phenomenon aren’t fully understood yet, researchers have identified some trends and potential causes.

What causes déjà vu?

There are a few theories about the cause of déjà vu according to literature and cultural or religious traditions. These theories may involve different concepts ranging from reincarnation to unconscious memories. 

In an academic review of research on the topic, a connection between frequent déjà vu and certain neurological conditions, such as temporal lobe epilepsy, has been made. In individuals with this condition, a sense of déjà vu may precede the onset of a seizure. People who experience focal seizures may suddenly feel an intense déjà vu before the seizures occur.

In neurologically healthy individuals, the underlying causes are still unknown. Some various theories, connections, and findings include:

• Less gray matter.One study compared gray matter volume in the brain between healthy subjects that did and did not experience déjà vu. It found that the volume was inversely correlated with the frequency of the phenomenon. In other words, those who had less gray matter volume in a certain part of the brain tended to experience déjà vu more frequently.
• A brief lag in neural transmission. Other research postulates that it’s caused by a brief change in the normal speed of neural transmission. The result of this temporary lag is “a slightly longer separation between identical messages received from two separate pathways.” You can think of this as the brain taking an extra second to process a memory it just made. So when it does, you recognize it as a past memory.
• A brief split in a perceptual experience. The research cited above also proposed that déjà vu could be caused by “a brief split in a continuous perceptual experience that is caused by distractions and gives the impression of two separate perceptual events.” If your brain gets distracted for a split second while you’re taking in a new experience and then returns to the experience, it might process the first moments of it as separate—a past memory.

Who is more likely to experience déjà vu?

Again, researchers are still in the process of discovering why some people may experience déjà vu more than others if they don’t have a neurological condition.

There may also be a link to stress and tiredness since both can affect short-term or long-term memory. Interestingly, another frequently cited study found a correlation between more frequent déjà vu and people who:

• Tend to remember their dreams
• Are well-educated and/or have a high income
• Travel frequently
• Are politically liberal

Yet another study found a link between frequent déjà vu and the use of the flu medications amantadine and phenylpropanolamine—including one case study where a person had several instances of déjà vu per hour until they stopped taking the medication. In other words, this relatively mysterious occurrence in the brains of those who do not have a neurological condition may be linked to a variety of causes or contributing factors. More research is necessary in order to know for sure.

When is déjà vu a cause for concern?

Déjà vu seems to be a relatively common, harmless phenomenon in most cases. However, there are some instances when it may be a sign of a condition that requires medical attention. According to the Cleveland Clinic, if you’re experiencing déjà vu as often as several times a month, you may want to consult a neurologist. This is especially true if it’s accompanied by unusual dream-like memories, a loss of consciousness, a racing heart, or a feeling of fear. In a case like this, it’s possible that an underlying neurological condition may be at play.

Even if you only experience déjà vu occasionally and it's not accompanied by other symptoms, it can be an unsettling, uncomfortable feeling. Some people in this situation may find it helpful to speak with a therapist about it. Simply vocalizing the experience to share it with someone else may feel calming, and a counselor can help you address any fears that may be associated with it. In addition, if a condition like anxiety or depression is causing you to react more strongly to an occurrence like this, a mental health professional can help you manage your symptoms.

Seeking therapy can be a unique process that depends on the individual. Some feel more comfortable connecting virtually with a therapist from their home. Since research suggests that this format can provide similar benefits to in-person sessions, it’s a viable option for those who prefer it. A virtual therapy platform like BetterHelp can match you with a therapist who you can speak with via phone, video, or chat to address the concerns and challenges you may be facing. Or, you can seek a provider in your area for face-to-face sessions. It’s typically best to choose the method that feels right for you.