Depression is a medical condition that affects your mood, resulting in persistent feelings of sadness, disinterest, and apathy. It can lead to serious complications, including difficulty living everyday life and even suicidal thinking. There is no known cause, but doctors have identified a variety of factors that are linked with depression, including biological differences, hormones, certain life experiences, and family history. There are three important neurotransmitters involved in understanding the chemistry of depression: Serotonin: regulates mood, appetite, sleep, social behavior, memory, and sexual desire. Dopamine: important for pleasure and reward, decision-making, motivation, and arousal. Norepinephrine: regulates blood pressure and heart rate in response to stress and affects alertness and motor function. Prescription drugs often target one or more of these neurotransmitters and allow for them to hang around longer so you feel their positive effects.