Occasional and temporary anxiety is a normal part of life.It helps to direct our attentional resources to pertinent information in the environment and mobilise appropriate behaviour in response.Persistent or excessive anxiety is pathological. Would such anxiety cause any deleterious effects on brain? Linda Mah and colleagues ( Canada) review the present evidence to answer this question.
Amygdala is key in threat detection.Prefrontal cortex play crucial role in threat appraisal. Hippocampus helps to build the contextual sense of the event. Balanced activities in these systems result in emotional regulation.
In anxiety disorders, detection threshold is low, amygdala become hyperactive and PFC control over amygdala is poor.Hippocampus fails to discriminate between threat and safety cues (impaired discriminative conditioning) and this lead to overgeneralisation of fear stimulus.
It is well known that anxiety is a risk factor for disorders like depression.Significant psychosocial stress in middle age is shown to increase the risk for developing Alzheimer’s disease 20 years later.Presence of anxiety among those with Mild cognitive impairment can also increase the risk of conversion to dementia.
Anxiety increase glucocorticoids and this lead to hippocampal atrophy and diminished neurogenesis. This may explain the cognitive dysfunctions associated with anxiety. Persistent anxiety can cause loss of dendrites and spines in Pre frontal cortex.
Stress-induced damage to the hippocampus and PFC is not completely irreversible. Antidepressants ( desipramine, SSRI) and Lithium as well as CBT can restore some of the above brain changes.There is a range of evidence ( mostly animal studies) to support this idea.
Pathological anxiety can cause damages (structural and functional) to brain. Interventions can mitigate these changes. It is not known whether anxiety interventions can reduce the risk of developing neuropsychiatric conditions (dementia/depression).
Summary of the article
Can anxiety damage the brain? Mah L, Szabuniewicz C, Fiocco AJ. Curr Opin Psychiatry. 2016 Jan;29(1):56-63.PMID: 26651008