Choice A rationale:

Chronic stress is known to activate the Hypothalamic-Pituitary-Adrenal (HPA) axis, which leads to increased cortisol production. While cortisol is important for various physiological functions, chronic elevation of cortisol due to stress can actually have detrimental effects on the brain. Elevated cortisol levels have been associated with impaired neurogenesis (the formation of new neurons) and synaptic plasticity (the ability of synapses to change and adapt), both of which play crucial roles in maintaining cognitive function and mental health.

Choice B rationale:

This statement is not accurate. Chronic stress typically leads to hyperactivity, not hypoactivity, of the HPA axis, resulting in increased levels of cortisol. The increased cortisol levels can negatively impact neurogenesis and synaptic plasticity, which are key factors in depression and cognitive function.

Choice C rationale:

This is the correct statement. Chronic stress triggers hyperactivity of the HPA axis, causing elevated levels of cortisol. While cortisol is meant to help the body cope with stress in the short term, chronic elevation can lead to adverse effects on the brain. High cortisol levels have been linked to impaired neurogenesis and synaptic plasticity, contributing to the development of depression and cognitive deficits.

Choice D rationale:

This statement is not accurate. Chronic stress tends to lead to hyperactivity of the HPA axis and elevated cortisol levels. Reduced cortisol levels, as suggested in this choice, are not commonly associated with chronic stress and its impact on depression.