Depression (Major Depressive Disorder) is a serious mood disorder characterized by a persistent feeling of sadness, loss of interest, and reduced energy. It negatively affects how you feel, think, and behave, often causing significant disruptions to daily functioning and physical well-being.Key SymptomsDepression is more than just a fleeting bad mood or feeling blue. Symptoms must last for at least two weeks to be considered clinically significant and can range from mild to severe:Emotional: Persistent sadness, tearfulness, emptiness, hopelessness, or irritability.Cognitive: Trouble concentrating, making decisions, or remembering things.Physical: Unexplained aches, headaches, or cramps; significant weight or appetite changes; and chronic fatigue.Behavioral: Loss of interest in previously enjoyed hobbies, social withdrawal, and disruptions in sleep (insomnia or oversleeping).