What are the symptoms of clinical depression?

Although the main symptom of clinical depression is a feeling of sadness and hopelessness, other symptoms are also present. Changes in appetite, including eating more or less than usual; lack of interest in activities; a loss of sexual desire; difficulties in concentrating; and feelings of worthlessness are some of the other symptoms. Major depression can also cause people to sleep too much or to suffer from insomnia. Fatigue, slowed movements, unexplained body pain, and irritability are also signs of depression.