Psychological stress is caused by a stimulus that induces the brain to react with different mechanisms of the endocrine, immunological and nervous systems [7].

The skin is constantly exposed to a wide range of stress agents that can cause signs of aging in the skin. It has long been acknowledged that some of these triggers come from the environment, UV radiation, chemical products, smoking and environmental changes. This may cause allergies, infections, the production of free radicals and metabolites [7].

The brain and skin share the same ectodermic origin and therefore have a close relationship [8]. Both the skin and nervous system resulted simultaneously during embryonic development from the same primary germ layer. It has also been shown that neuronal signaling pathways contain a protein that is also present in skin cells. This may explain how the activities in the central nervous system can also influence cellular function in the skin and the appearance of many inflammatory, autoimmune and allergic diseases that may be triggered during stressful periods [7].

Although there is limited evidence linking psychological stress to skin aging, there are an increasing number of publications that cite research showing the relationship between psychological stress to neurological, endocrine, and immune reactions that influence the mechanisms which are known to cause aging [9] (Fig. 4.2).

In response to acute stress a part of the brain called hypothalamic-pituitary-adrenal (HPA) is activated, triggering the production and release of glucocorticoids, such as cortisol and some neurotransmitters called cathecolamines, particularly dopamine, norepinephrine and epinephrine. Cathecolamines activates an area called amygdala, which appears to trigger an emotional response to a stressful event. The brain releases neuropeptide S, a small protein that modulates stress by decreasing sleep and increasing alertness and a sense of anxiety. Cathecolamines also suppress areas at the front of the brain concerned with short-term memory, concentration, inhibition, and rational thought that allows a person to react quickly. At the same time, neurotransmitters signal the hippocampus to store the emotionally loaded experience in long-term memory. The stress response also affects the heart, lungs and circulation. The skin response to acute stress moves blood flow away to support the heart and muscle tissue. Once the threat has passed and the effect has not been harmful, the stress hormones return to normal. This is known as the relaxation response [9].