stressA scientific review paper published this month in the journal, Current Opinion in Psychiatry, warns that chronic stress can lead to an elevated risk of neuropsychiatric disorders. The review was led by the Rotman Research Institute at Baycrest Health Sciences, and it surveyed a number of animal and human studies. The researchers concluded that stress, anxiety and fear seem to affect the brain’s neurocircuitry, and are implicated in the development of many cases of depression and dementia.

Of course, anxiety, fear and stress are impossible to avoid. They are part of the human condition, and they are usually temporary. When we face an exam, or are awaiting the results of medical tests or an employment evaluation, we experience stress. But generally, once the situation resolves, the stress disappears as well.

It is only when stress, anxiety and fear become frequent or chronic that they begin to significantly impact the activities of daily life in areas such as work, school and relationships. Chronic stress is categorized as a pathological state, caused by a prolongation of the brain’s acute physiological response. This prolongation negatively impacts our immune, metabolic and cardiovascular systems. It actually causes atrophy of the hippocampus, the area of the brain responsible for long-term memory and spatial navigation.

Dr. Linda Mah, clinician scientist at Baycrest’s Rotman Research Institute and the lead author of the review, writes:

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 studies included in the Rotman research were based on animal models, as well as neuroimaging studies of healthy individuals and clinical populations experiencing stress and anxiety. Dr. Mah and her colleagues examined key structures in the neurocircuitry activated by fear and anxiety: the amygdala, medial prefrontal cortex, and hippocampus. They observed similarities in the patterns of abnormal brain activity with individuals experiencing fear and anxiety, and chronic stress, specifically an overactive amygdala (which reacts to emotional responses) and an underactive PFC (the areas of the brain that govern emotional reactions through cognitive appraisal). These comprise the “see-saw” relationship that was first identified more than ten years ago by world-famous neurologist and depression researcher, Dr. Helen Mayberg.

Dr. Mah, who is also an assistant professor of Psychiatry in the Department of Geriatric Psychiatry at the University of Toronto, offered her opinion that damage to the hippocampus and PFC caused by stress is “not completely irreversible.” She cited evidence that treatment with antidepressants and physical activity have both been shown to increase hippocampal neurogenesis (the generation of new, healthy cells). She added:

Looking to the future, we need to do more work to determine whether interventions, such as exercise, mindfulness training and cognitive behavioural therapy, can not only reduce stress but decrease the risk of developing neuropsychiatric disorders.

In an earlier paper published in October 2014, Dr. Mah found strong evidence that anxiety may speed the development of full-blown Alzheimer’s disease in patients diagnosed with mild cognitive impairment.