Centenarians 'depression prone'
Depression is known to be widespread among elderly people
It may bring a congratulatory telegram from the Queen but reaching 100 is no guarantee of a happy, contented, old age, US research suggests.
A study by researchers at Temple University in Philadelphia of 244 people aged 100 or over found one in four showed clear signs of depression.
However, fewer than a third of these had been officially diagnosed by a GP.
Age Concern painted a similar picture, with its figures showing two million UK pensioners affected by depression.
People who suffer from depression tend to have a high risk of mortality, so it's puzzling to see higher numbers among the oldest old
Dr Adam Davey
The US has about 60,000 people over 100 and this is expected to quadruple as general life expectancy rises and the "baby boomer" generation arrives at extreme old age.
In the UK there are thought to be more than 9,000, the majority of them women, and that figure is currently rising at 5% a year, with some population predictions suggesting a total of more than 58,000 by 2032.
Despite this, studies focusing entirely on centenarians are still relatively uncommon.
The Temple study, presented at the Gerontological Society of America's annual meeting, found 25% of their subjects had "clinically relevant" levels of symptoms, yet only 8% reported having a current diagnosis of depression.
Dr Adam Davey, who led the study, said: "Centenarians are still rare, and depression hasn't been studied thoroughly in this group.
"We've found that it's a very under-diagnosed condition among people over 100 years old, yet it's one of the most easily treated forms of mental illness.
"People who suffer from depression tend to have a high risk of mortality, so it's puzzling to see higher numbers among the oldest old."
Fastest growing age-group
In the UK, mental health charities and those catering for older people both complain that depression is not taken seriously in the elderly.
Marjorie Wallace, from Sane, said: "It should come as no surprise that people of all ages can suffer from depression, and we welcome this contribution to our understanding of this condition amongst those aged 100 or more.
"With an increasingly ageing population it is vital that governments in the UK and elsewhere provide appropriate treatment for this illness regardless of how old someone is.
"Untreated depression can have profound consequences, yet with the right support it is possible to prevent much unnecessary suffering."
Gordon Lishman, from Age Concern, said: "Despite people aged 85 and over being the fastest growing age group in Britain, many NHS services are not tailored to meet the needs of our ageing society.
"The neglect of older people's mental health ruins lives and must no longer be ignored."
The charity is running a campaign, "Down but Not Out", which aims to draw attention to the mental health of older people.