Here are the clinical symptoms of depression , plus what signs look like in daily life. Depression is a common and serious mental health condition. In this article, learn about 14 of the common symptoms . Read about the symptoms of depression in adults, which can be mild, moderate or severe. Symptoms can also be classed as psychological, physical and social. Depression (major depressive disorder) is a common and serious medical illness that negatively affects how you feel, the way you think and how you act. Fortunately, it is also treatable.