Depression is an emotional state characterized by feelings of gloom, inadequacy, and excessive sadness that leads to withdrawal. It is caused by various factors and can take different forms such as major depression or persistent depressive disorder. Common signs include a persistently low mood, loss of interest in activities, changes in appetite or sleep, lack of energy, feelings of worthlessness, difficulty concentrating or making decisions. Depression affects people of all ages and demographics and can increase the risk of suicide if left untreated.