Depression causes neurological changes in the brain resulting in mental, emotional and physical changes. Identified causes of these changes are alteration in the production of neurotransmitters such as serotonin and norepinepherine, and the functioning of neurotransmitter receptor sites. The American Psychology Foundation (2009) refers to these neuropsychosocial changes as neurovegetative signs of depression. They include alterations in sleep patterns, fatigue, and loss of appetite.
Endogenous Catecholamines (Stress Hormones)
It is important to recognize the connection between stress and depression. According to the National Institute of Mental Health (NIMH) severe acute stress and chronic stress can lead to depression. The physical effects of depression are compounded by the body’s stress response. Dr. Don Colbert, MD reports in his book Stess Less (2008) that over 1,400 physical and chemical reactions in conjunction with greater than 30 hormones and neurotransmitters are involved in the body’s stress response.
During a stress response, the body’s adrenal glands secrete three important hormones called epinephrine, norepinephrine, and cortisol (a corticosteroid). These stress hormones are responsible for the symptoms experienced when the body is in fight or flight mode. Elevated heart rate and blood pressure, elevated blood glucose and shunting of blood from the digestive organs to the brain help the body respond to perceived threats. Physical effects range from dry mouth, rapid and irregular heart rate, anxiety and loss of appetite.
According to the NIMH (2008) prolonged stress and depression affect corticosteroid production, which can result in stress hyperglycemia. According to the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health, hyperglycemia increases incidence of neuropathy, kidney disease, hypertension and poor wound healing.
Depression weakens the immune system, particularly natural killer T-cells which help protect the body from carcinogens (cancer-causing agents). A weakened immune system also affects the body’s inflammatory response. The NIHM reports that this physical effect of depression has been related to an increased incidence of osteoarthritis, asthma, heart disease and autoimmune disorders.
According to the American College of Cardiology (2005) the release of endogenous catecholamines (stress hormones) causes vasoconstriction and increased heart rate. This leads to an increase in blood pressure which requires the heart to work harder. The neurovegetative symptoms of depression make a person less likely to exercise, eat or sleep properly. These behaviors increase a person’s risk for developing cardiovascular complications such as high blood pressure, atherosclerosis, heart attack, and stroke.