Atopic dermatitis (AD) is a complex disease traditionally involving interaction of genetic, environmental, and immunologic factors. Recent studies suggest psycho-neuro-immunologic factors and emotional stress are important in its evolution. The observations that internal (bacterial infections) or external (psycho-logic) stressors may induce AD flares is explained by studies showing that stress impairs the skin barrier function and favors a shift in immunity toward a T helper type 2 cell/allergic response. Furthermore, those with AD appear to have an inherited hypothalamic deficiency that impairs normal hypothalamic-pituitary-adrenal axis function. Neuropeptides released in the skin may also mediate neurogenic inflammation, including mast cell degranulation. AD causes significant stress and impaired quality of life in patients and their family members. Psychologic and stress-reduction interventions were recently shown to improve patient well-being, and to significantly improve cutaneous manifestations.
Psoriasis is a common dermatologic disorder with psychiatric comorbidity that often goes undetected and untreated. Psoriasis has higher associations with psychiatric illness than do other dermatologic conditions. We conducted a comprehensive qualitative review of all published medical literature on psoriasis and psychiatric comorbidities since 2005. We found that psoriasis patients suffer psychiatric and psychosocial morbidity that is not commensurate with the extent of cutaneous lesions. Biologic therapies and nonpharmacologic psychosocial interventions show promise in treating comorbid psychiatric illness. The main limitations of this review are the low quality of published studies and the infrequent use of basic science endpoints in reporting treatment outcomes. The literature examining the psychiatric comorbidity of psoriasis is expanding but remains of variable quality. Stronger studies will be necessary to more accurately estimate comorbidities and help identify and comprehensively treat suffering patients.
Psychoneuroimmunology (PNI) is a discipline that has evolved in the last 40 years to study the relationship between immunity, the endocrine system, and the central and peripheral nervous systems. In this manner, neurotransmitters, hormones, and neuropeptides have been found to regulate immune cells, and these in turn are capable of communicating with nervous tissue through the secretion of a wide variety of cytokines. Of critical importance is the effect of products of the CNS and nerves on the maintenance of the delicate balance between cell-mediated (Th1) and humoral (Th2) immune responses. A good example of how this concept operates in vivo becomes evident when analyzing the effects of stressors. Chronic stress affects significantly the function of the immune system as well as modifies the evolution of a variety of skin diseases, as psychosocial interventions have proved to be effective in their therapy.
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