The bill for treating those with mental health disorders is expected to rise
The cost of caring for people with mental health disorders in England is expected to spiral, a report says.
This is due to a predicted rise in the number of people with dementia, the King's Fund study argues.
In total, it will cost £47bn a year, compared with £22.5bn in 2007, the think tank said.
The early detection of mental problems and prompt therapy could help the wider economy by keeping those affected in work, the report added.
The ageing population means that diseases of old age are set to rocket in the next two decades, according to the King's Fund.
It is predicting a 61% rise - hundreds of thousands of extra cases a year.
This, coupled with inflation in healthcare costs, is almost completely responsible for the rise in the annual bill shared between the NHS and social care services.
Niall Dickson, the chief executive of the King's Fund, said: "The fact that we are living longer is cause for celebration, but it will mean that the health and social care systems will have to cope with a dramatic increase in the number of people suffering from dementia."
The incidence of other mental disorders, such as depression and schizophrenia, is expected to stay roughly the same, said the report.
In 1997, in addition to the £22.5bn directly spent by the NHS and social care providers, it is estimated that the mental disorders cost the economy an additional £26.1bn, as people affected were unable to work.
Researchers suggested that early diagnosis and treatment of more people with conditions such as depression could help reduce this.
As well as calling for increased detection and treatment of mental disorders, the King's Fund report also called on future governments to ensure that funding for services keeps pace with the likely increase.
A spokesman for the Department of Health said that it recognised dementia as a "significant health challenge" for society.
She added: "That is why we are determined to bring dementia out of the shadows and later this year we'll launch the first ever national strategy to improve the quality of life for people with dementia and their families."
Mental health charities welcomed the release of the report.
Mind chief executive Paul Farmer said: "This makes a robust economic case to invest more broadly in mental health because it's worth it."
And Andrew McCulloch, from the Mental Health Foundation, said: "The scale of the problem regarding old age and dementia is a serious worry."
But Marjorie Wallace, from Sane, said: "We are concerned that the increasing need to channel resources into the treatment of dementia could force savings to be made elsewhere, in particular through cuts to psychiatric beds and inpatient care."
Rebecca Wood, chief executive of the Alzheimer's Research Trust, said: "With dementia research severely underfunded compared with other health problems like cancer, we are sleepwalking towards a healthcare timebomb.
"The government must act now by drastically increasing its investment in research."