Chronic depression and dementia are often seen together in older people. Why do these happen? What are the mechanisms?
Studies have found that chronic stress may lead to the alterations in the hypothalamic-pituitary-adrenal (HPA) axis, as well as serotonergic and immune dysfunctions (Leonard and Myint, 2009). These alterations may in turn result in anxiety and depression disorders.
Specifically, the alterations in the HPA axis and the immune malfunctions may often cause neurodegenerative problems in the hippocampus, prefrontal cortex and amygdalae in the older people (Leonard and Myint, 2009).
Studies in psychoneuroimmunology (PNI) have shown that chronic stress and depression may lead to the increased levels of pro-inflammatory cytokines and glucocorticoids (Leonard and Myint, 2009). Such alterations may in turn result in behavioral symptoms related to depression. These mechanisms may help explain the connections among stress, depression, dementia, and inflammation in the elderly.
Leonard BE, Myint A. The psychoneuroimmunology of depression. Hum Psychopharmacol. 2009 Apr;24(3):165-75. doi: 10.1002/hup.1011.