George has gone into a deep depression after the death of his wife, for whom he had provided daily ...

George has gone into a deep depression after the death of his wife, for whom he had provided daily care for over 2 years after her first stroke. What role might cortisol play?
 
  a. Over-response of the hippocampus may have led to reduced cortisol in the bloodstream, which is associated with depression.
  b. Under-response of the hippocampus may have led to reduced cortisol in the bloodstream, which is associated with depression.
  c. Consistently elevated levels of cortisol due to stress can overwhelm the hippocampuss feedback loop and lead to excess levels of cortisol in the bloodstream, which is associated with depression.
  d. Erratic levels of cortisol due to stress can disrupt the hippocampuss feedback loop and lead to erratic levels of cortisol in the bloodstream, which is associated with manic depression.