Key Symptoms: Persistent feelings of sadness, hopelessness, or emptiness for at least two weeks. Individuals may also experience a loss of interest or pleasure in activities once enjoyed, fatigue, difficulty concentrating, changes in appetite or sleep patterns, and thoughts of death or suicide.

Impact: Major depression can severely impair an individual's ability to function at work, school, or in relationships, and can have a significant impact on daily life.

Treatment: MDD is often treated with a combination of medication (such as antidepressants) and therapy, such as cognitive-behavioral therapy (CBT) or interpersonal therapy (IPT).

Key Symptoms: Chronic, low-level depression lasting for at least two years. The symptoms are less severe than major depression but can still cause significant distress and interfere with daily functioning. People with PDD may experience periods of normal mood, but the underlying depressive symptoms often persist.

Impact: Individuals with PDD may find it difficult to experience joy or satisfaction in life, and may feel like they've "always been depressed."

Treatment: Treatment often includes psychotherapy, medication, and lifestyle changes. Antidepressants and CBT are common treatment options.

Key Symptoms: A form of depression that occurs at a specific time of year, usually during the winter months when there is less sunlight. Symptoms include low energy, difficulty concentrating, sleep disturbances, and weight gain or loss.

Impact: SAD can significantly affect an individual's mood, energy levels, and overall productivity during the darker months.

Treatment: Light therapy, antidepressant medications, and psychotherapy are common treatment approaches for individuals with SAD.

Key Symptoms: A subtype of depression that includes mood reactivity (i.e., the ability to feel better in response to positive events), increased appetite, excessive sleep, and a sensation of heaviness in the arms and legs.

Impact: Atypical depression can lead to significant emotional distress and dysfunction in everyday activities.

Treatment: Treatment may involve antidepressants (such as SSRIs) and psychotherapy. Atypical depression may respond differently to treatment than other forms of depression.

Key Symptoms: Characterized by alternating periods of extreme mood states, including depressive episodes and manic or hypomanic episodes. During depressive episodes, individuals experience typical symptoms of depression, while manic episodes involve heightened energy, racing thoughts, impulsivity, and sometimes risky behaviors.

Impact: Bipolar disorder can affect many aspects of life, including relationships, work, and personal well-being, due to the dramatic shifts in mood.

Treatment: Bipolar disorder is usually treated with a combination of mood stabilizers, antidepressants, and therapy to help manage the extreme mood swings and maintain balance.

Key Symptoms: This type of depression affects women after childbirth. Symptoms include feelings of sadness, irritability, excessive fatigue, difficulty bonding with the baby, and changes in sleep and appetite. Unlike "baby blues," which are temporary mood changes after childbirth, postpartum depression is more intense and longer-lasting.

Impact: Postpartum depression can make it difficult for new mothers to care for themselves and their baby, and can have a significant impact on family dynamics.

Treatment: Postpartum depression is treatable with therapy, medications (such as antidepressants), and support from family and healthcare providers.