Mood disorders are a category of illnesses that describe a serious change in mood. Illness under mood disorders include: major depressive disorder, bipolar disorder (mania - euphoric, hyperactive, over inflated ego, unrealistic optimism), persistent depressive disorder (long lasting low grade depression), cyclothymia (a mild form of bipolar disorder), and SAD (seasonal affective disorder).
The majority of people with mood disorders are able to find treatments that work. Talk therapy, medication or a combination of both help individuals feel better and change situations in their lives that may be contributing to their illnesses (substance use, harmful relationships, etc.).