The mother of a 19-year-old male is convinced his bipolar condition was caused by his drinking and drug use. Which of the following statements is true regarding bipolar disorder?
a. Patients with bipolar disorder have a better prognosis than patients with unipolar depression.
b. Patients with bipolar disorder usually do not require lifelong treatment compared to patients with major depression if they abstain from drugs and alcohol.
c. Bipolar disorder has a stronger genetic etiology than major depression.
d. Bipolar disorder is more common than depression in the United States.