Cyclothymia is a type of chronic mood disorder widely considered to be a milder form of bipolar disorder, and is characterized by numerous extreme mood disturbances, with periods of hypomanic symptoms. The symptoms include euphoria, extreme optimism, inflated self-esteem, rapid speech, racing thoughts, aggressive behavior, lack of consideration for others, agitation, massively increased physical activity, risky behavior, increased drive to perform or achieve goals, increased sexual drive, decreased need for sleep, tendency to be easily distracted, inability to concentrate, and periods of mild or moderate depression. Other symptoms are difficulty making decisions, problems concentrating, poor memory recall, guilt, self-criticism, low self-esteem, pessimism, self-destructive thinking, constant sadness, apathy, hopelessness, helplessness and irritability. Also common are quick temper, poor judgment, lack of motivation, social withdrawal, appetite change, lack of sexual desire, self-neglect, fatigue, and insomnia. The exact cause of cyclothymia is unknown. It is known that major depression, bipolar disorder and cyclothymia often co-occur within families.