Narrowing down risk factors that are specific to Alzheimer’s disease and other dementia-related conditions has become increasingly more important seeing as some of these factors follow a person throughout their life. A recent study conducted by researchers from the University of Southern California has found that people who have suffered from high anxiety levels at some point in their lifetime have a 48 percent higher risk for dementia compared to those who have not experienced anxiety.

"Anxiety, especially in older adults, has been relatively understudied compared to depression," said Andrew Petkus, a postdoctoral research associate of psychology in the USC Dornsife College of Letters, Arts, and Sciences, in a statement. "Depression seems more evident in adulthood, but it's usually episodic. Anxiety, though, tends to be a chronic lifelong problem, and that's why people tend to write off anxiety as part of someone's personality."

Petkus and her colleagues examined 28 years of data taken from the Swedish Adoption Twin Study of Aging, which included 1,082 twins, both fraternal and identical. Participants were asked to complete in-person tests every three years, several questionnaires, and be screened for dementia. Researchers compared the dementia risk for those who reported high anxiety to those who reported lower anxiety levels.

Participants with anxiety who end up developing dementia "are people that experience more than usual symptoms of anxiety," Gatz explained. The research team found that participants with high levels of anxiety also had high levels of stress hormones, like cortisol. Past research has shown the continually high levels of cortisol can damage various areas of the brain, including the hippocampus, which is responsible for memory storage, and the frontal cortex, which is responsible for high-level thinking.

"They are people who you would say operate at a 'high level of anxiety,'" said Margaret Gatz, a professor of psychology in the USC Dornsife College of Letters. "They are frantic, frazzled people. Those in the high anxiety group were about 1.5 times more likely to develop dementia"

Findings also revealed that the relationship between anxiety and dementia was stronger among fraternal twins who had only one twin develop dementia compared to identical twins. This could point to genetic factors shared by anxiety and dementia. Although a number of recent studies have examined the link between dementia and psychological variables, such as anxiety and depression, none have established a link between anxiety and dementia that was independent of depression’s role.

Source: Gatz M, Pederson N, Kremen W, Wetherell J, Reynolds C, Petkus A.Anxiety is associated with increased risk of dementia in older Swedish twins. Alzheimer's & Dementia. 2015.