Depression. Artwork depicting a person suffering from depression. Depression is a mental state characterized by excessive sadness. People with mild depression may suffer anxiety, mood swings and bouts of crying. People with more serious depression may additionally suffer from loss of appetite, tiredness, difficulty sleeping and disturbed concentration. A sufferer may eventually become completely withdrawn. Depressive illness may be triggered by viral infections, hormonal disorders or by psychological or social factors. Methods of treatment include psychotherapy, antidepressant drugs and electroconvulsive therapy (only used in severe cases)