Bipolar disorder
"Bipolar" literally means "two poles" or two extremes in how much energy the brain has. Sometimes, a person can experience something called mania. Mania is when a person's brain goes into a high-energy state. When in a high-energy state, mania can cause extreme emotions such as panic attacks or extreme happiness such as euphoria. This feeling is often followed by a period of depression, which is a low-energy state. A person who is depressed may act sad or hopeless. People with bipolar disorder switch between these two states.