Someone close to me has been feeling down for a while. what is the most common symptom of depression usually?

Depression symptoms: Common symptoms of depression include: feelings of sadness, a loss of interest in activities you used to enjoy, difficulty concentrating, change in sleep and/or appetite, fatigue, feelings of hopelessness, poor motivation, and irritabiliy. The person may also have problems functioning at work or school. If they have the majority of these symptoms they may have depression.