If you are like most people, chances are that you have experienced déjà vu. French for ‘already seen’, it is that thrilling yet eerie feeling that you have encountered a situation or been to a place before, knowing fully well that it is not the case. For most people, the feeling is sudden and fleeting. But for a 23-year-old British resident it became a prolonged affair that lasted for over eight years.

According to the international team of researchers, who published the findings of this unusual instance in the Journal of Medical Case Reports in December 2014, the young man's symptoms began in 2007. While he had always suffered from anxiety, his condition worsened when he entered university. Believing a break would help, he decided to take some time off.

But instead of helping it resulted in creating a vicious cycle of déjà vu - the feeling that he had encountered things before - over and over again. While some episodes would last for just minutes, others went on for a long time. The patient felt as though he was constantly 'trapped in a time loop.'

By 2010, the young man's symptoms had become so severe that he had given up watching television, listening to the radio and reading newspapers.

What was interesting is that until this case, researchers had seen recurring déjà vu occur only in patients suffering from seizures. They had therefore believed that it was caused by a temporary glitch in the brain's processing of incoming information.

Christine Wells, the researcher from Sheffield Hallam University that led the latest study says that they could, however, find no signs of neurological problems in this young man's case. This led them to speculate that persistent déjà vu may also be a side effect for people that suffer from severe anxiety issues. But in order to confirm that researchers need to conduct further studies on other patients with similar symptoms.

Fortunately these cases are rare and for most people déjà vu is a fleeting sensation that is gone before they even realize it. According to researchers, déjà vu is most frequently experienced by people between the ages of 15 and 20. They suspect that the hippocampus the part of the brain that plays an important part in memory is responsible for the sensation. However, its sudden and unforeseen occurrences makes it impossible to pinpoint the exact cause of déjà vu. There are a few theories that have been put forth.

According to Dr. Akira O' Connor, a psychologist from the University of St. Andrews, déjà vu may be caused by a "misfiring of brain neurons." She believes it occurs when the part of the brain that sends signals related to familiarity and memory has a momentary glitch and sends them out of turn.

Professor Anne Cleary at Colorado State University thinks that it occurs when a person encounters something that is genuinely familiar like the shape of a structure or the way a room is laid out. This causes the brain to believe that it has seen it all before, creating a sense of déjà vu. Then there are those that believe that déjà vu is a spiritual occurrence and others that think it is the work of aliens.

So the next time you experience that eerie feeling of 'already seen,' take a moment to reflect on one of these theories. Maybe you can help researchers pinpoint the reason behind this phenomenon that is just another example of the mysterious workings of the human brain.

Resources:jmedicalcasereports.com,bbc.com,livescience.com