Evidence from a major review of published research suggests that chronic stress and anxiety damage key brain regions involved in emotional responses, thinking and memory.
Lead author Dr Linda Mah, from the Baycrest Centre for Geriatric Care in Toronto, Canada, said: "Pathological anxiety and chronic stress are associated with structural degeneration and impaired functioning of the hippocampus and the prefrontal cortex (PFC), which may account for the increased risk of developing neuropsychiatric disorders, including depression and dementia."
The review paper, published in the journal 'Current Opinion in Psychiatry', pooled findings from a number of recent studies of stress and fear conditioning in animals, and people undergoing brain scans.
Dr Mah's team looked specifically at neural circuits linked to fear and anxiety in three brain regions, the amygdala, PFC, and hippocampus.
A see-saw pattern was seen in response to chronic stress with the amygdala, associated with emotional responses, becoming over-active and the PFC under-active.
The PFC contains "thinking" areas of the brain that help to regulate emotional responses by appraising them in a rational way.
Temporary episodes of anxiety, fear and stress - experienced before an exam or job interview, for instance - are part of normal life.
But the scientists point out that when such acute emotional reactions become chronic they can "wreak havoc" on immune, metabolic and cardiovascular systems, and damage the brain.