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Feeling of déjà vu can arise in moments of stress, sleep deprivation, and neurological changes linked to memory, according to specialists. The phenomenon usually lasts a few seconds, but frequent or intense episodes can indicate imbalances in brain function and require medical investigation.
The feeling of déjà vu occurs when a new experience evokes the impression of having been lived before, even without any concrete memory associated with the situation. Although the episode usually lasts a few seconds, specialists warn that frequent repetition can indicate changes in brain function.
Despite being considered common and generally harmless, the phenomenon continues to pique scientific interest because it involves mechanisms linked to memory and recognition. Researchers relate this perception to temporary failures between brain systems responsible for identifying familiarity and retrieving contextualized memories.
According to psychiatrist Oswaldo Petermann Neto, from the Doctoralia platform, the brain has different structures for recognizing something familiar and for retrieving complete memories. “The brain has distinct systems: one that recognizes something as familiar and another that retrieves contextualized memories. In déjà vu, there is an activation of familiarity without a real associated memory,” he states.
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In the assessment of neurologist Diogo Haddad, from Alta Diagnósticos, in São Paulo, the phenomenon also has a consistent neurological explanation. “From a neurological point of view, we believe it is a mismatch between memory systems. The brain recognizes something as familiar before it can identify where that memory comes from,” he explains.
How the brain interprets memories and familiarity
Contrary to what many people imagine, memory does not function as a simple file stored linearly within the brain. To recognize environments, voices, faces, or events, different brain areas work together in an extremely fast and almost imperceptible process.
In this mechanism, perception, attention, emotions, and previous experiences are processed simultaneously so that the brain can differentiate what is new from what has already been experienced. When a temporary failure occurs in this integration, the feeling of familiarity can arise incorrectly.
The hippocampus plays an important role in the formation and organization of memories, while the temporal lobe participates in the processing of emotions, language, and recognition. Momentary alterations in these regions can make the brain interpret a new experience as something already known previously.
Still, specialists emphasize that isolated episodes do not usually represent a significant neurological problem. Tired people, young adults, or individuals subjected to strong emotional pressure frequently report déjà vu without presenting significant alterations in clinical exams.
Stress, anxiety, and sleep deprivation can favor episodes
In addition to the natural functioning of memory, emotional and physical factors also directly influence the occurrence of déjà vu. Prolonged situations of anxiety, intense stress, or few hours of sleep increase brain excitability and hinder the proper processing of information.
With an overloaded brain, the checking between new experiences and old memories can lose precision for a few moments. According to Petermann Neto, mental fatigue interferes precisely with this mechanism responsible for validating whether a certain situation has actually happened before.
“This can generate a false sense of recognition, as if the brain identified something that, in reality, is new,” says the psychiatrist. The explanation helps to understand why the phenomenon tends to appear more frequently during periods of emotional overload or irregular routine.
In addition to anxiety disorders, some dissociative disorders and, in rarer situations, psychotic disorders can involve feelings of strangeness, perceptual distortions, or false familiarity. In these scenarios, medical analysis considers the set of symptoms presented by the patient.
When déjà vu can be linked to epilepsy
Among the neurological conditions associated with the phenomenon, temporal lobe epilepsy is one of the most notable for specialists. In these patients, déjà vu can appear as a neurological aura, functioning as an initial sign of a focal epileptic seizure.
According to Haddad, episodes related to epilepsy usually present greater intensity and can occur repeatedly over time. In some cases, the sensation is accompanied by sudden fear, altered consciousness, memory lapses, or automatic behaviors.
Among the main warning signs are an intense feeling of strangeness, momentary loss of contact with the environment, brief confusion, and recurrent episodes of false familiarity. Even so, specialists emphasize that not every déjà vu indicates epilepsy or another serious neurological disorder.
Epilepsy is characterized by abnormal electrical discharges in the brain capable of causing recurrent seizures. When these changes occur in the temporal lobe, areas linked to memory, emotions, and perception are directly affected.
Frequency of episodes requires medical attention
Although occasional episodes are considered normal, the recommendation changes when déjà vu becomes frequent, prolonged, or interferes with daily routine. In these cases, specialists advise seeking medical evaluation to investigate possible neurological or psychiatric changes.
“Clinical evaluation is recommended when episodes become frequent, intense, prolonged, or are accompanied by altered consciousness, memory lapses, or an intense feeling of strangeness,” advises Petermann Neto.
Depending on the frequency of symptoms and the patient’s history, exams such as electroencephalogram and magnetic resonance imaging may be requested to analyze brain activity and rule out structural or electrical changes.
In addition to neurological conditions, the use of alcohol, drugs, and certain medications can also interfere with the circuits responsible for memory and perception. Therefore, lifestyle habits, sleep quality, and family history are part of the clinical investigation.
In most situations, déjà vu remains merely a curious experience of human mental functioning. However, when episodes begin to deviate from the usual pattern or appear accompanied by other symptoms, specialists recommend attention to identify possible silent changes in the brain.
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