A depressive episode in bipolar disorder involves a period of low mood along with several of the following symptoms: overwhelming sadness, low energy and fatigue, lack of motivation, feelings of hopelessness, loss of enjoyment in previously pleasurable activities, difficulty concentrating and making decisions, uncontrollable crying, irritability, changes in sleep (increased need for sleep, insomnia, or excessive sleep), a change in appetite, and thoughts of death or suicide (suicidal ideation).