Which of the following is a well-established difference between major depression and bipolar disorder?

a. Depression is more common than bipolar disorder in the general population.
b. Depression is more common in men, whereas bipolar disorder is more common in women.
c. Depression has a stronger genetic basis than bipolar disorder.
d. Depression is acute, whereas bipolar disorder is chronic.

Answer: a. Depression is more common than bipolar disorder in the general population.