Depression, antidepressants and immune system: A new look to an old problem

Abstract

Background: The monoaminergic hypothesis of depression does not answer certain questions, such as "what are the causes of the monoaminergic disturbances?" and "how to explain the existence of 30% refractory patients to antidepressants?". Therefore, other theories have emerged, such as those focusing on the immune and endocrine systems. Objectives: To analyze the role of the immune-inflammatory system on depression and, furthermore, the interactions between antidepressants and this system, from basic and clinical points of view. Methods: literature review was carried out in the Medline and SciElO databases. Results: Patients suffering of chronic stress and depression present an activation of both inflammatory responses and hypothalamic-pituitary- adrenal axis, which, directly or indirectly, influence neurotransmission. Therefore, the use of antidepressants not only increases the availability of neurotransmitters in the synaptic cleft, but also changes the pattern of Th1 immune response - pro-inflammatory - to the Th2, which is antiinflammatory. Moreover, it is known that patients who do not respond to antidepressant treatment have hyperactive immune-inflammatory response system. However, there are several controversies in the literature, and evidences suggest a different immune profile according to the type of depression. Discussion: The understanding of the neuroimmune aspects of depression might contribute to a better comprehension of the biological basis of this disorder and, therefore, to a new perspective in the search for a more effective therapy.