What are the Health Consequences of Chronic Stress?
Chronic stress can exert considerable body-wide health effects. It can contribute to the onset or worsening of many types of ailments. The following discussion highlights some of the more common conditions to which chronic stress often contributes.
One of the most widely recognized health effects of chronic stress is heart disease. Through the effects of cortisol and catecholamines, and by disrupting circadian rhythms through sleep disturbance, chronic stress has been shown to impair nervous system regulation of cardiac function,49 and can cause high blood pressure, arrhythmia, and vascular inflammation leading to atherosclerosis and blood clots.50 Prolonged stress at home and at work has been clearly linked to increased risk of coronary artery disease and cardiac events including heart attack and stroke.12,51 A recent meta-analysis highlights the influence of work stress on heart disease risk: after analyzing data from more than 740,000 men and women, researchers found that people who work 55 or more hours per week have a 12% increased risk of coronary artery disease and a 21% increased risk of stroke compared with those who work less.52
Acute stress can also pose a threat to the heart. Studies have noted the incidence of heart attack increases following acutely stressful events such as earthquakes and World Cup soccer championships.53 Takotsubo cardiomyopathy, a sudden weakening of the heart muscle that mimics the symptoms of heart attack or angina and is potentially fatal, is another example of the danger of acute stress to the heart. Also known as stress cardiomyopathy, broken heart syndrome, and apical ballooning syndrome, Takotsubo cardiomyopathy typically occurs a few hours after a severe physical or emotional trauma and is most common in postmenopausal women.54,55
Psychiatric and Neurological Disorders
Persistently high cortisol levels, a marker of chronic stress, can trigger changes to neuronal structure and reduce brain plasticity (the ability to make new neuronal connections).56 Chronic stress is closely associated with several common neuropsychiatric disorders, including depression, anxiety, dementia, and Alzheimer disease.
Inflammation in the brain triggered by stress-related signaling appears to underlie a number of these illnesses.57 In Alzheimer disease, stress-related immune dysfunction appears to weaken the brain’s ability to clear amyloid-beta, a protein involved in Alzheimer disease development and progression.58,59 Early life, repetitive, or chronic stress may also reduce the activity of nerve growth factors, especially brain-derived neurotrophic factor (BDNF), involved in formation of new nerve connections.60-62 Low levels of BDNF are associated with mood disorders as well as learning and memory deficits.62 Furthermore, these stress-related changes may be encoded epigenetically, altering nerve system plasticity and function in lasting ways.63
A growing body of evidence suggests that the neurohormones of the stress response can promote the initiation and progression of cancer.64,65 Furthermore, chronic stress may be associated with behaviors, such as smoking, substance abuse, overeating, and decreased physical activity, that increase the risks of certain cancers.66,67 Coping with a cancer diagnosis, symptoms, and treatment is inherently extremely stressful for some individuals,68,69 yet a high burden of stress may negatively impact response to cancer treatment and prognosis.64,70,71
The mechanism by which stress influences cancer is likely to be multifaceted, but the cornerstone may be immune dysregulation, marked by decreased immune surveillance and systemic inflammation. HPA axis dysregulation suppresses immune defenses against cancer, and chronic systemic inflammation creates conditions that support cancer initiation, progression, and metastasis.72,73 Inflammation may stem from other stress-induced sequelae, including weight gain and metabolic disturbance, disruption of the gut microbiome, and epigenetic alterations72; in turn, inflammation can contribute to these processes.74 In addition, stress may affect cancer development by desynchronizing circadian regulation of biological activities.29,75
Metabolic Disturbance: Why Does Stress Make it Hard to Lose Weight?
One of the most important functions of the stress response is to ensure that adequate energy is available to cope with stressful circumstances. During episodes of acute stress, appetite is suppressed to reserve attention for fight or flight, and extra energy in the form of glucose is freed from stored fats and carbohydrates. Under conditions of chronic stress, however, appetite is typically up-regulated and cravings for high-sugar, high-fat, high-calorie foods can intensify as a result of long-term hyperstimulation of the HPA axis and its complex interactions with appetite-regulating neurohormones such as ghrelin and leptin. For reasons that are not entirely clear, an increased appetite as a reaction to chronic stress is more pronounced in women than men.10,76
To make matters worse, chronic stress and HPA axis dysregulation are associated with insulin resistance and type 2 diabetes , as well as fat tissue growth and obesity.77,78 In one study, salivary cortisol tests showed disturbances in the diurnal rhythm of cortisol release were correlated with body mass index (BMI) and waist circumference, a measure of visceral fat and one of the cardiovascular risk factors in metabolic syndrome.79 These metabolic consequences of long-term stress then promote widespread inflammatory signaling that damages blood vessels and increases cardiovascular risk.80,81 Systemic inflammation also affects the nervous system, contributing to mood and cognitive disorders, and creates a vicious cycle of increased HPA axis activation.10,82
Although widely believed that chronic stress can lead to weakened thyroid function, there is little evidence as of the date of this writing to support this notion. In one study, hair cortisol levels were higher in adults with overt hypothyroidism than in healthy adults, and were correlated with higher body weight and BMI; however, in participants with subclinical hypothyroidism, a condition characterized by normal to slightly abnormal lab values and possibly symptoms of hypothyroidism, hair cortisol levels were not significantly different from those of healthy participants.83 Findings from preliminary studies indicate stress may contribute to the onset of autoimmune hypothyroidism; however, a review of these studies was unable to confirm the connection.84 On the other hand, evidence from animal studies suggest hypothyroidism may trigger HPA axis dysregulation and, when chronic, reduce adrenal output.85,86
Additional Health Conditions Stress Can Worsen
Virtually any health condition can be negatively affected by stress. In addition to those already discussed, the following are some of the disorders and diseases that stress may impact:
- Atopic dermatitis88
- Autoimmune diseases89
- Chronic fatigue syndrome90
- Upper and lower respiratory infections91
- Irritable bowel syndrome93
- Pain disorders95,96
- Sexual dysfunction97