The same is true of individuals who score very high on the test's depression scale. The risk is 40 percent higher for individuals who score very high on both anxiety and pessimism scales.

"There appears to be a dose-response pattern, in other words: the higher the scores the higher the risk of dementia,” says Yonas Geda, M.D., a Mayo Clinic neuropsychiatrist and the study's lead investigator.

Although it is common to see personality changes such as pessimism, depression, agitation or withdrawal once a person develops dementia, the Mayo Clinic investigators believe that pessimism and depression are more likely to be risk factors for dementia rather than early manifestations of the disease due to the significant time gap between the time of the personality test (in the 1960s) and the appearance of dementia or cognitive impairment (anytime between the 1960s and 2004).

Dr. Geda and colleagues extracted a sample of approximately 3,500 individuals from 50,000 individuals who took the Minnesota Multiphasic Personality Inventory (MMPI) as part of a research project - not for psychiatric reasons - at Mayo Clinic between 1962 and 1965. The test takers ranged in age from 20 to 69 when they took the test.

The Mayo Clinic investigators advise some caution in determining if one's personality traits may predispose to dementia. "One has to be cautious in interpreting a study like this,” says Dr. Geda. "One cannot make a leap from group level data to the individual.”

This test assesses thoughts, feelings, attitudes, physical and emotional symptoms, and life experiences. In 2004, Dr. Geda and fellow investigators used a structured interview of the individuals to arrive at a standard diagnosis of dementia or cognitive impairment.; Source: Mayo Clinic