Symptoms of depression can begin at any age and for no apparent reason.
Even major events that affect others, such as the destruction of the World Trade Center in New York, can be a trigger. In such circumstances, it's obviously normal to experience grief or sadness for a period of time. However, if the depression persists for an extended period of time or if it seems to worsen as time goes on, professional mental healthcare may be in order. Other situations can also trigger depression. One is the birth of a child.