Figure 3. Individuals with chronic emotional disorders such as depression or who experience chronic stress may be subject to chronic physiological stress responses characterized by chronic overstimulation of the hypothalamic–pituitary–adrenal (HPA) axis and sympathetic nervous system (SNS). The resultant dysregulation of these systems may lead to decreased cortisol variability, hypercortisolemia, high norepinephrine levels, autonomic dysfunction, elevated resting heart rates, and other peripheral affects that are not shown. The chronic stress response is also characterized by a prolonged recovery to physiological stimulation and to enhanced cardiovascular reactivity to novel stressors.