Researchers warn of a financial disaster waiting to happen among one-in-three Europeans, as the cost of treating brain disorders, such as depression, insomnia, Parkinson's and stroke, has more than doubled in just six years, according to a study.

In 2010, a survey revealed that one in three people in Europe suffers a brain disorder or care for somebody with one, bringing to almost 800 billion euro (£689 billion) the amount spent annually across Europe for brain disorder treatments.

In the UK alone, 9.7 million people are believed to have a brain disorder, at a cost of more than 134 billion euro (around £116 billion) a year.

Experts examined 30 countries and 19 groups of disorders, including anxiety disorders, addictions, brain tumours, childhood and adolescent developmental disorders, dementia, eating disorders, epilepsy, migraine, multiple sclerosis, Parkinson's, sleep disorders, stroke and traumatic brain injury.

The Telegraph reports, the researchers are experts from universities and hospitals across Europe. They warn their figures are ''very conservative'' and almost certainly an underestimate.

The team said dealing with brain disorders represents ''the number one economic challenge for European healthcare now and in the future.''

Mood disorders, such as depression and bipolar, are thought to be the most costly group, at more than 113 billion euro (£97 billion) each year, with 33.3 million sufferers.

Dementia ranks second at just over 105 billion euro (£90 billion), with more than 88 billion euro (£76 billion) of that coming from costs such as social care.

The number of people suffering brain disorders is expected to rise as people live longer.

''We have to emphasise that the burden of disorder of the brain will likely increase further, simply due to the continuing life expectancy in Europe,'' the experts said.

''Because of the ageing European population, degenerative disorders are particularly destined to become more common, such as dementia, Parkinson's disease and stroke, but anxiety and mood disorders are also very prevalent at high age.''

The team's report, calling for more investment in science and teaching, was published in the journal European Neuropsychopharmacology.

''Mental disorders represent a real challenge for society," said Professor Hans-Ulrich Wittchen, from the European College of Neuropsychopharmacology.

''They're not only highly prevalent but also very expensive - not because of their treatment costs, which are relatively low, but because of the indirect costs that come with the high levels of long-term disability they cause,'' he added.