Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Mood Disorders ?
    ### Response:
    Most people feel sad or irritable from time to time. They may say they're in a bad mood. A mood disorder is different. It affects a person's everyday emotional state. Nearly one in ten people aged 18 and older have mood disorders. These include depression and bipolar disorder (also called manic depression).
    