Cynics are three times more likely to develop dementia than those who have faith in humanity, a study has shown.
Believing that others are motivated by selfishness or that they lie to get what they want appears to radically increase the risk of cognitive decline in later life.
Cynicism has previously been linked to health problems such as heart disease, but this is the first time it has been associated with dementia.
"These results add to the evidence that people's view on life and personality may have an impact on their health," said Dr Anna-Maija Tolppanen, the lead researcher at the University of Eastern Finland, whose study is published online in the journal 'Neurology'.
Academics asked nearly 1,500 people with an average age of 71 to fill out a questionnaire to measure levels of cynicism.
They were asked how much they agreed with statements such as "I think most people would lie to get ahead".
Those taking part were monitored for eight years, during which time 46 of them were diagnosed with dementia. The academics found that those who had scored highly for cynicism were three times more likely to have developed dementia than those with low scores.
However, responding to the study's conclusions, charities cautioned that the early symptoms of Alzheimer's and dementia could make people more cynical about life.
Dr Doug Brown of the Alzheimer's Society in Britain said: "There were far too few people in this study that actually developed dementia to be able to draw any firm conclusions.
"However, we do know that some people with dementia experience symptoms of paranoia, confusion and mood changes which can lead to cynicism and distrust." (© Daily Telegraph, London)