<p>Depression is one of the most common neuropsychiatric disorders.&nbsp; However, its etiology is not completely understood.&nbsp; This literature review aims to discuss and integrate scientific literature of depression as a biopsychosocial phenomenon (Engel, 1977).&nbsp; The cognitive theory of depression (Beck, 2008) and the cognitive neurobiological model of depression (Disner, Beevers, Haigh &amp; Beck, 2011) serve as a theoretical framework for a holistic understanding of depression.&nbsp; Research about the neurobiological, socio-environmental and cognitive aspects of depression is discussed by sections.&nbsp; According to the literature reviewed, it is concluded that the different biological, socio-environmental and cognitive aspects of depression are nourished and modified by each other.&nbsp; Therefore, for the comprehension, diagnosis and treatment of affective disorders such as depression, it is necessary to consider their biopsychosocial character. The development of more interdisciplinary research is proposed, as well as a focus on a multidisciplinary approach to treatment and the expansion of depression theories and models.</p>