Depression is not only hard to endure, it is also a risk factor for heart disease and dementia. “Depressive symptoms can occur in adults for many reasons. If you are experiencing mood or cognitive changes that last for more than a few weeks, it’s a good idea to bring this up with your doctor or consult a mental health specialist to help sort out possible causes,” says Dr. Nancy Donovan, an instructor in psychiatry at Harvard Medical School. The four most common types of depression are major depression, persistent depressive disorder

Major depression

The classic depression type, major depression is a state where a dark mood is all-consuming and one loses interest in activities, even ones that are usually pleasurable. Symptoms of this type of depression include trouble sleeping, changes in appetite or weight, loss of energy, and feeling worthless. Thoughts of death or suicide may occur. It is usually treated with psychotherapy and medication. For some people with severe depression that isn’t alleviated with psychotherapy or antidepressant medications, electroconvulsive therapy may be effective.

Persistent depressive disorder

Formerly called “dysthymia,” this type of depression refers to a low mood that has lasted for at least two years but may not reach the intensity of major depression. Many people with this type of depression are able to function day to day, but feel low or joyless much of the time. Other depressive symptoms may include appetite and sleep changes, low energy, low self-esteem, or hopelessness.

Bipolar disorder

People with bipolar disorder—once known as manic-depressive disease—have episodes of depression. But they also go through periods of unusually high energy or activity. Manic symptoms look like the opposite of depression symptoms: grandiose ideas, unrealistically high self-esteem, decreased need for sleep, thoughts and activity at higher speed, and ramped-up pursuit of pleasure including sex sprees, overspending, and risk taking. Being manic can feel great, but it doesn’t last long, can lead to self-destructive behavior, and is usually followed by a period of depression. Medications for bipolar disorder are different from those given for other depression types, but can be very effective at stabilizing a person’s mood.

Seasonal affective disorder

This type of depression emerges as days get shorter in the fall and winter. The mood change may result from alterations in the body’s natural daily rhythms, in the eyes’ sensitivity to light, or in how chemical messengers like serotonin and melatonin function. The leading treatment is light therapy, which involves daily sessions sitting close to an especially intense light source. The usual treatments for depression, such as psychotherapy and medication, may also be effective.

Depression types unique to women

Although women are at higher risk for general depression, they are also at risk for two different depression types that are influenced by reproductive hormones—perinatal depression and premenstrual dysphoric disorder .

Perinatal depression

This type of depression includes major and minor depressive episodes that occur during pregnancy or in the first 12 months after delivery. Perinatal depression affects up to one in seven women who give birth and can have devastating effects on the women, their infants, and their families. Treatment includes counseling and medication.

PMDD

This type of depression is a severe form of premenstrual syndrome, or PMS. Symptoms of PMDD usually begin shortly after ovulation and end once menstruation starts. Selective serotonin reuptake inhibitors, such as fluoxetine and sertraline , may reduce symptoms.