Multiple sclerosis is an auto-immune disease where the body attacks the protective coating, known as myelin, around brain cells.

The research, published in Lancet Neurology, could help doctors screen for the disease and start interventions earlier in a new direction for finding the root cause of the disease. "Proving that people with multiple sclerosis have already changed their behaviour in the five years before even the earliest medical recognition of the condition is very important because it means we have to look beyond those five years to understand how it is caused," said researchers from the University of British Columbia in Canada’s Vancouver.

The team examined health records of 14,000 people with multiple sclerosis for over a 20-year period and compared them to the health records of 72,000 people without the disease. They were looking for something called a prodrome, an early set of symptoms that can indicate the onset of a disease.

Prodromes have been identified for other neurological conditions like Alzheimer's and Parkinson's diseases. The recognition of these prodromes has provided clues about how the diseases might begin and have stimulated new research into causes or triggers.

"There's something going on here that makes this population of people unique," said first author Jose Wijnands. "When other degenerative brain diseases have a prodrome, it suggests that something may be happening,” senior author of the study Helen Tremlett explained.