Mood disorders are a category of mental health conditions that involve persistent changes in a person's emotional state. These disorders can range from mild to severe and can significantly impact a person's ability to function day-to-day. Common mood disorders include depression, bipolar disorder, and seasonal affective disorder. Research in this area aims to better understand the causes, symptoms, and treatment options for mood disorders in order to improve outcomes for individuals affected by these conditions. This research often involves studying genetic, environmental, and psychological factors that contribute to the development and progression of mood disorders, as well as testing the efficacy of various interventions such as therapy, medication, and lifestyle changes.