Anxiety is associated with helplessness, physiological arousal or somatic symptoms and is associated with anticipated threats while depression is characterized by hopelessness, anhedonia or social withdrawal and is preceded by loss (Stein & Hollander, 2002). In the tripartite model, anxiety and depression share a common element: they both have general negative affectivity, representing negative valence emotions and general distress with symptoms such as fear, sadness, and tension.
Anxiety, having the unique component of the physiological hyperarousal of the “fight-or-flight” response distinguishes from depressive disorders which have, on the other hand, a dimension of low positive affectivity, described as the ability to experience pleasure and/or engage in the environment. Patients with anxiety disorders are described as having high levels of general negative affectivity accompanied by physiological hyperarousal while patients with depressive disorders have high general negative affectivity; and of positive affectivity; and those with the comorbid condition or mixed expression would have high general negative affectivity, low positive affectivity, and hyperarousal symptoms (Soares & Gershon, 2003).
There are several processes that may influence the developmental course of mood and anxiety symptoms, and disorders during childhood and adolescence. The development of anxiety during early childhood is associated with early stressful experiences that occur under conditions of uncontrollability and uncertain helplessness. These may be followed by a sense of helplessness and uncertain hopelessness that is associated with the experience of mixed anxiety and depression. Finally after frequent stressful experiences and the development of patterns of negative cognitive interpretations of these events, a combination of helplessness-hopelessness may emerge, leading to a more purely depressive syndrome.
The role of both biological and environmental factors in the relationship between anxiety and depression are also being associated according to some evidences. Using behavioral genetics methods, shared and nonshared environmental factors, as well as genetic factors, are involved in the development of symptoms of anxiety and depression, as well as in the relationship between these symptoms. More than 50% of the variance accounted for the environmental factors on both anxiety and depression symptoms. Genes accounted for a greater portion of the variance in depressive symptoms (approximately 30%) than anxiety symptoms (approximately 10%); on the other hand, shared environmental factors accounted for more of the variance in anxiety (> 30%) than depressive (between 10% and 20%). Genes, on the other hand, accounted for the huge majority (approximately 80%) of the correlation between anxiety and depression symptoms.
These analyses suggest that both environmental and genetic factors play an important role in the development of depression and anxiety, and an even greater role in the association between these symptoms. Therefore there may be genetic factors that account for nonspecific effects in the development of internalizing symptoms of both anxiety and depression, while exposure to certain types of environmental experiences may determine the degree to which symptoms of anxiety, depression, or both, are manifested.
Moreover, there may be developmental differences in exposure to environmental factors that contribute to depression as opposed to anxiety, and/or in the cognitive process that lead to be interpretation of environmental experiences that lead to one or the other type of symptoms. Anxiety and depression may become increasingly differentiated with age, and symptoms of mixed anxiety and depression may lead to the onset of the full manifestation of an anxiety disorder or major depression, or may represent a link between the early development of anxiety and the later development of depression (Sameroff, Lewis, & Miller, 2000).
Sameroff, A. J., Lewis, M., & Miller, S. M. (2000). Handbook of Developmental Psychopathology: Springer.
Soares, J. C., & Gershon, S. (2003). Handbook of Medical Psychiatry: Informa Health Care.
Stein, D. J., & Hollander, E. (2002). Anxiety Disorders Comorbid With Depression: Social Anxiety Disorder, Post-Traumatic Stress Disorder, Generalized Anxiety Disorder and Obsessive-Compulsive Disorder: Informa Health Care.