Distinguishing between clinical depression and a case of "the blues" isn't always easy. Deciding when ordinary mood swings indicate a more serious problem requires looking at several different criteria and keeping in mind that depression affects everyone differently.

Change in Sleep Patterns

Changes in sleep patterns can be an indicator of a variety of problems, one of which is clinical depression. Some people who are suffering from depression feel that they want to sleep constantly, while others start to have trouble with insomnia.

Change in Appetite

Depression often triggers changes in a person's appetite. A person suffering from clinical depression may binge on sweets to cover up unpleasant emotions or start to skip meals altogether.

Trouble Concentrating

Difficulty concentrating at work or school can be a sign of clinical depression, especially in people who have previously had no trouble remaining focused on a task for long periods of time.

Changes in Social Behavior

Clinical depression can make it hard to enjoy being around family and friends. If you or someone you know has been avoiding opportunities for socialization for several weeks at a time, this should be considered as a warning sign for depression.

Loss of Interest in Hobbies

A person suffering from clinical depression will often express no interest in activities that once brought great pleasure, whether those are biking, reading, drawing or other recreational pursuits.

Source:

Mayo Clinic: Depression