MDD involves persistent feelings of sadness, hopelessness, and loss of interest in activities once enjoyed. Symptoms last at least two weeks and may include:

• Fatigue, sleep disturbances, or appetite changes

• Difficulty concentrating

• Thoughts of worthlessness or guilt

• Suicidal thoughts in severe cases

Bipolar Disorder includes episodes of depression alternating with periods of mania or hypomania. Depressive episodes in bipolar disorder mirror MDD symptoms but are part of a larger mood cycle.

• Bipolar I: Involves manic episodes with or without depressive episodes

• Bipolar II: Involves hypomanic episodes and more pronounced depressive episodes

PMDD is a severe form of premenstrual syndrome (PMS), with intense mood symptoms like depression, irritability, and anxiety that occur in the luteal phase of the menstrual cycle (just before a period starts). Symptoms often include:

• Mood swings and sadness

• Irritability or anger

• Fatigue and sleep changes

• Physical symptoms like bloating or breast tenderness

Dysthymia involves a chronic, low-level depressed mood lasting at least two years (one year for children and adolescents). Symptoms may not be as severe as MDD but are persistent and can interfere with daily functioning, including:

• Low energy or fatigue

• Poor concentration

• Feelings of hopelessness