The American Psychiatric Association’s Diagnostic Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) classifies depressive disorders as the following: Clinical depression (major depressive disorder): A diagnosis of major depressive disorder means you’ve felt sad, low or worthless most days for at least two weeks while also having other symptoms such as sleep problems, loss of interest in activities or change in appetite. This is the most severe form of depression and one of the most common forms. Persistent depressive disorder (PDD): Persistent depressive disorder is mild or moderate depression that lasts for at least two years. The symptoms are less severe than major depressive disorder. Healthcare providers used to call PDD dysthymia. Disruptive mood dysregulation disorder (DMDD): DMDD causes chronic, intense irritability and frequent anger outbursts in children. Symptoms usually begin by the age of 10. Premenstrual dysphoric disorder (PMDD): With PMDD, you have premenstrual syndrome (PMS) symptoms along with mood symptoms, such as extreme irritability, anxiety or depression. These symptoms improve within a few days after your period starts, but they can be severe enough to interfere with your life. Depressive disorder due to another medical condition: Many medical conditions can create changes in your body that cause depression. Examples include hypothyroidism, heart disease, Parkinson’s disease and cancer. If you’re able to treat the underlying condition, the depression usually improves as well. There are also specific forms of major depressive disorder, including: Seasonal affective disorder (seasonal depression): This is a form of major depressive disorder that typically arises during the fall and winter and goes away during the spring and summer. Prenatal depression and postpartum depression: Prenatal depression is depression that happens during pregnancy. Postpartum depression is depression that develops within four weeks of delivering a baby. The DSM refers to these as “major depressive disorder (MDD) with peripartum onset.” Atypical depression: Symptoms of this condition, also known as major depressive disorder with atypical features, vary slightly from “typical” depression. The main difference is a temporary mood improvement in response to positive events (mood reactivity). Other key symptoms include increased appetite and rejection sensitivity. People with bipolar disorder also experience episodes of depression in addition to manic or hypomanic episodes.