ABSTRACT
One of the greatest challenges of depression is that it is common, af¯icting large segments of the population. Indeed, its frequency is the reason that it has been termed the `` common cold'' of psychological disorders. When considering how frequent depressive disorders may be, it is helpful to consider two measures, one concerning how many depressed people there are in a given period, and the other indicating how many people experience signi®cant depression in their lifetimes.
