European neuroscientists said on Tuesday that the withdrawal by some big drugmakers from research into illnesses like depression, schizophrenia and Alzheimer's could halt the discovery of new drugs.

A report published by the European College of Neuropsychopharmacology (ECNP) said brain diseases and mental disorders like depression, dementia and addiction account for more a third of the burden of disease in Europe, but public and corporate research and development (R&D) funding is being cut.

"These are dark days for brain science," David Nutt, a professor of Neuropsychopharmacology at Imperial College London and a former president of the ECNP told a briefing in London.

Some European big pharma companies such as GlaxoSmithKline and AstraZeneca have in recent years backed away from brain research, citing the difficulty and expense of finding new drug candidates.

The ECNP report said public funding for research in Europe into disorders of the brain lags significantly behind similar investment in the United States.

Yet experts estimate that in any given year, almost 80 million Europeans, or 27 percent of the European Union's population, are affected by disorders of the brain.

"The issue here is not just that a very key part of Europe's knowledge economy is under serious threat, it's that the withdrawal of research resources means the slowdown, and even outright cessation in some areas, of new treatments being developed," said Guy Goodwin, a co-author of the report and head of Oxford University's psychiatry department. "This will inevitably affect patient well-being."

Nutt and Goodwin said a major part of the problem in persuading public and private organizations to fund research into mental illness is the stigma that it carries.

Unlike research into cancer or heart disease, they said, which commands huge public support and can return a swifter profit to drugmakers who find successful treatments, research into brain diseases is seen as difficult, expensive and ultimately less fruitful.

According to the report, the economic cost to the EU region of brain diseases and mental disorders was conservatively estimated at $555 billion a year in 2005, the last time a full costing analysis was done. That cost, the authors said, far exceeds the cost to the region of any other disease area, including heart disease and cancer.

"The human cost, in terms of illness-related work disability, social role failure and premature death, is similarly immense," they wrote. And as Europe's population ages, those costs are likely to rise further.

Alastair Benbow, executive director of the European Brain Council, said the report showed the urgency of the region's funding crisis in neuropsychiatric drug discovery.

"If steps aren't taken now ... to stimulate research and investment in both the public and private sector, the field could really suffer lasting damage," he said.