The essential features of cyclothymic disorder are recurrent mild mood highs or lows that do not meet the diagnostic criteria for the number of symptom entries, severity, and duration of manic episodes or depressive episodes. 1. The patient’s state of mind is unstable for at least two years, during which there are cycles of mild mania or mild depression, with rapid transitions between mild manic and depressive symptoms lasting only a few days in each temporal phase. Periods of normal state of mind typically do not exceed 2 months. The patient’s social functioning is largely maintained. 2. Mild manic symptoms are mainly manifestations of heightened emotion, talkativeness, excitement, irritability, high self-evaluation, etc., and the degree and duration do not meet the criteria for manic episodes; depressive symptoms are mainly manifestations of depressed mood, diminished interest, decreased energy, pessimism, and self-blame, and the degree and duration do not meet the criteria for depressive episodes. Patients with cyclothymic disorder can usually improve and return to normal after active treatment, but there is a tendency of recurrent episodes, so once diagnosed, active treatment should be provided and regular follow-ups should be conducted to avoid delaying the condition.