The Fact That Bright Light May Be an Effective Treatment

The fact that bright light may be an effective treatment for seasonal affective disorder suggests that ________

A) this is a not a real form of depression as any response to light is merely a placebo effect.
B) this form of depression is produced by a malfunctioning biological clock that needs resetting.
C) changes in circadian rhythms underlie most forms of depression.
D) seasonal affective disorder is a unique entity that should not be categorized with other forms of unipolar depression.