Déjà vu, the eerie suspicion that you've seen or done something before, is experienced by more than 70 percent of people at some point.

Trapped in a time loop: That's how one man felt because of his recurring déjà vu episodes. Unlike the vague, fleeting sensation most people experience in déjà vu, his episodes were persistent and long.

The 23-year-old British man started to have "frightening" episodes of déjà vu shortly after starting college, said the researchers who detailed his unusual case in a new report. For minutes, and sometimes even longer, he would feel that he had already experienced all of those moments. The episodes grew in intensity and became debilitating.

"Rather than simply the unsettling feelings of familiarity which are normally associated with déjà vu, he complained that it felt like he was actually retrieving previous experiences from memory, not just finding them familiar," the researchers said. [16 Oddest Medical Case Reports]

Three years after the experiences began, the young man could no longer even watch TV or read the paper because he would have a disturbing feeling that he had encountered the content before, the researchers said.

The haunting sensation was stronger than just a feeling of familiarity. The man said he felt that at every present moment, he was reliving the past.

What made the case even more peculiar was that the man didn't suffer from any of the neurological conditions previously reported in people who experience frequent déjà vu episodes. Instead, he suffered from anxiety, suggesting that anxiety disorders could be more related to déjà vu than previously thought, according to the report, which was published Dec. 8 in the Journal of Medical Case Reports.

Déjà vu in the brain

Scientists have yet to find a complete explanation for déjà vu, which is French for "already seen," but a popular idea is that the false sensation of familiarity is the result of a failure in the brain's memory system, which resides in the temporal lobe of the brain.

"Most explanations of déjà vu suggest that it's a phenomenon that arises from activity within the temporal lobe. Some kind of mistimed firing of neurons, perhaps — a temporary glitch in our processing of incoming information," said Christine Wells, a psychologist at Sheffield Hallam University in the United Kingdom who co-authored the new report of the man's case.

"A key structure within the temporal lobe is the hippocampus, which is heavily involved in memory," Wells said. "We have every reason to believe that's the area that's involved in déjà vu."

In fact, although almost anyone can have an episode of déjà vu every once in a while, more frequent and intense forms of the phenomenon are usually seen in people who have seizures in the temporal lobe, a condition called temporal lobe epilepsy.

In this man's case, doctors looked for signs of seizures, but neurological examinations, including EEGs (electroencephalograms) and brain scans, didn't turn up anything. His brain activity, as far as doctors could measure, looked normal. And a set of psychological tests of his memory didn't reveal any major problem, either.

Could it be anxiety?

Although the researchers didn't find neurological clues that could explain this man's déjà vu, it is still possible that there are signs they missed, Wells said. The available technologies may not be sophisticated enough to pick up on what could be very subtle differences in the brain, she said.

The other explanation for the man's chronic déjà vu is his anxiety disorder.

"A lot of the previous research has focused — quite rightly — on temporal lobe epilepsy," Wells said. "But it is possible that there are other disorders, such as anxiety disorders, in which people experience déjà vu slightly more often than normal."

The young man's anxiety was so severe that he had to take a short break from college, and that's when his déjà vu episodes began. These episodes caused him even more anxiety and distress, possibly creating a vicious circle, the researchers said.

At one point, the déjà vu became fairly continuous — this happened right after the man took the hallucinogenic drug lysergic acid diethylamide (LSD), he told the researchers.

Still, the case of a single man cannot prove that there's a link between anxiety and déjà vu, the researchers said. But the case raises the question, and should be studied further, they said.

Email Bahar Gholipour. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.