6 types of depression

6 Types of Depression—and What You Should Know About Them

By Bailey Miller
Reviewed by Susan Ko, Ph.D.
October 27, 2023
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Clinical depression is a mood disorder that has a negative effect on how you think and feel, and on your ability to function in your daily life. Depression is common—it affects about 280 million people worldwide, according to the World Health Organization.

And although many people tend to associate the condition with feeling blue, there are actually many different types of depression, each with its own set of characteristics and symptoms.

Below are six common types, their symptoms, and causes.

1. Major Depressive Disorder (MDD)

The most common form of depression—12% of people worldwide, on average, experience MDD during their lifetimes, according to the National Institutes of Health (NIH).

Characteristics and Symptoms: People with MDD may experience persistent low mood, lack of interest in normally enjoyable activities, and feelings of sadness, guilt, or worthlessness that disrupt day-to-day life. Other MDD symptoms include changes in appetite and sleep, poor concentration, lack of energy, and, in severe cases, suicidal thoughts.

Causes: MDD is thought to be caused by a variety of factors, including neurotransmitter disturbances, genetics, severe stress, personality, and cognitive distortions.

2. Seasonal Affective Disorder (SAD)

Major depressive disorder with a seasonal pattern, commonly known as seasonal affective disorder, is a type of depression that begins and ends around the same time every year, following a seasonal pattern and where symptoms last for four to five months annually. SAD affects about 5% of people per year.

Characteristics and Symptoms: Typically, people diagnosed with SAD experience symptoms similar to MDD in the fall and winter months, when there’s less sunlight. Symptoms can also include oversleeping, overeating, weight gain, and social withdrawal, similar to feelings of “hibernation” that are both significant and debilitating.

Causes: Although the causes of SAD are not fully understood, research suggests that it's likely a combination of disrupted serotonin and melatonin levels and circadian rhythm caused by a lack of vitamin D, which is usually provided by sunlight.

3. Bipolar Disorder

The World Health Organization estimates that 40 million people experienced bipolar disorder in 2019, the most recent year that statistics are available. And the NIH estimates that 4.4% of adults in the United States will be affected by the disorder at some point in their lives.

Characteristics and Symptoms: Bipolar disorder is characterized by extreme shifts in mood, energy, activity levels, or concentration that cause significant difficulty and disruption to daily life. These changes in mood alternate between periods of high energy, elation, impulsivity, inflated self-esteem, or irritability and more depressive episodes. During depressive episodes, symptoms are similar to those of MDD.

Causes: Bipolar disorder is thought to be significantly affected by genetic predisposition and differences in the structure of and chemicals within the brain.

4. Persistent Depressive Disorder (PDD)

Previously known as dysthymia or chronic depressive disorder, PDD is believed to be a milder but more persistent form of MDD, affecting about 3% of the U.S. population.

Characteristics and Symptoms: People with PDD experience chronically low mood lasting at least two years.

Causes: The exact cause of PDD is still being researched, but some suggested risk factors include genetics, prior mental illness, high anxiety, psychological health, trauma, life stressors, and social and environmental factors.

5. Perinatal Depression

“Perinatal” refers to the period during pregnancy and up to a year after birth. Although depression that occurs after childbirth, known as postpartum depression, may be more widely known, depression can also strike during pregnancy, when it's known as prenatal depression. It's estimated that it affects 10% to 20% of pregnant people in the United States.

Characteristics and Symptoms: More than just the baby blues, perinatal depression is characterized by significant sadness, anxiety, fatigue, and/or functional impairment that lasts longer than two weeks and makes it difficult for people experiencing it to care for themselves and others.

Causes: Perinatal depression is likely caused by a combination of genetic and environmental factors, including a family history of depression, life stress, physical and emotional demands related to pregnancy and caring for a child, and changes in hormones related to pregnancy.

6. Premenstrual Dysphoric Disorder (PMDD)

Considered a more serious form of premenstrual syndrome (PMS), PMDD results in extreme distress and functional impairment in 5% to 8% of people who menstruate.

Characteristics and Symptoms: Although varying by individual, symptoms of PMDD may include depressed mood, anxiety and tension, persistent irritability, changes in appetite, difficulty concentrating, sleep disturbances, feeling overwhelmed, and lack of energy, aligning with the pattern of the menstrual cycle.

Causes: The exact causes of PMDD are unknown, but some risk factors associated with it include past trauma, cigarette smoking, obesity, and genetic factors.

Where to Get Help

If you find it difficult to function in your daily life, work, or relationships, consider reaching out to a mental health professional. The following organizations may also provide assistance: