A British student was forced to drop out of university after a bizarre case of chronic déjà vu left him unable to lead a normal life.
The 23-year-old even stopped watching TV, listening to the radio or reading newspapers and magazines because he believed he had seen it all before.
He told doctors he was "trapped in a time loop" and felt as if he was reliving the past moment by moment.
Details of the case have been revealed in a report published by the Journal of Medical Case Reports.
Doctors are baffled because the man, who is not named in the report, does not suffer from any of the neurological conditions usually seen in people who suffer frequent déjà vu. It is thought panic attacks might have triggered the phenomenon, or that LSD exacerbated it.
The author of the report, Christine Wells, a psychology expert from Sheffield Hallam University, said it could be the first case of a person experiencing persistent déjà vu stemming from anxiety.
Though most people experience occasional feelings of déjà vu, more frequent and intense forms are usually seen only in people who have seizures in the temporal lobe, a condition called temporal lobe epilepsy.
But brain scans showed no sign of seizures or neurological conditions in the man. Psychological tests to check his memory also failed to show any major issues.
The student first complained of symptoms of déjà vu early in 2007, shortly after starting university. He had a history of feeling anxious, particularly a fear of germs, which led him to wash his hands very often and to shower two to three times a day.
But his anxiety worsened when he began university. Anxiety and low mood led him to take a break from his studies, and he then began experiencing déjà vu.
By 2010, he was avoiding reading or watching TV because he felt as if he had already "encountered the content".
"Rather than simply the unsettling feelings of familiarity that are normally associated with déjà vu, our subject complained that it felt like he was actually retrieving previous experiences from memory, not just finding them familiar," said Wells.
"Most cases like this occur as a side effect associated with epileptic seizures or dementia.
"In this instance it appears as though the episodes of déjà vu could be linked to anxiety causing mistimed neuronal firing in the brain, which causes more déjà vu and in turn brings about more anxiety.
"If proved, this could be the first recorded instance of psychogenic déjà vu, which is déjà vu triggered by anxiety rather than a neurological condition.
"In relation to our case, distress caused by the déjà vu experience might itself lead to increased levels of déjà vu: similar feedback loops in positive symptoms are reported in other anxiety states, for example panic attacks.
"It is plausible on neurobiological grounds that anxiety might lead to the generation of déjà vu," Wells said.
Academics from the UK, France and Canada were called in for the study, led by Wells.
She is looking to undertake more research to discover a possible link between clinical anxiety and episodes of déjà vu.
"The case on its own cannot prove that there is a link between anxiety and déjà vu, but our findings raise the question and it should be studied further," she said.
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