Depression is a mental health condition that causes people to feel extremely sad, frustrated, angry, become unable to enjoy favorite activities, have difficulty sleeping, and lose energy or mental focus for two weeks or longer. It is different than being upset for a short period of time. Doctors sometimes call depression “clinical depression” or “major depressive disorder.”

Depression is the most commonly diagnosed mood disorder. It can affect children or adults, but it’s more common among adults. About 15% of people experience depression at least once in their lives. Sometimes it runs in families.

Women are more prone to depression, possibly due to hormone fluctuations. Older adults may be more likely to experience depression than younger adults, but depression is not a part of healthy aging. Among older adults, retirement, coping with serious illness, or grieving for lost loved ones may contribute to developing depression.

Untreated depression may lead to suicidal thoughts or suicide attempts. Seeking treatment can help to improve depression in nearly every instance, although treatment may take weeks to months to achieve full beneficial effects, and depression may recur in some people.

Depression is a mood disorder that affects millions of Americans of all ages. It may cause people to feel hopeless and pessimistic. They may lose interest in seeing friends or doing enjoyable activities, instead choosing to isolate at home. They may become preoccupied with thoughts about death or suicide.

Sadness is a hallmark of depression, but depression differs from the fleeting sadness that people may feel in response to upsetting news or situations. Sadness doesn’t endure for weeks on end; it typically resolves within hours or days. With depression, however, sadness and other negative emotions last for long periods.

People who experience depression may feel that they should “snap out of it,” then feel upset that they can’t. Chemical changes in the brain may dictate depressive feelings, so treatment is necessary. Medication, talk therapy, or brain stimulation treatments should help to resolve symptoms.

Doctors don’t know exactly what causes depression, but they believe that chemical imbalances in the brain may be a contributing factor for some people. Different chemicals within the brain help to influence people’s thoughts, feelings, and behaviors. Too little or too much of certain chemicals may lead to feelings of depression.

Depression may run in some families, but doctors aren’t sure if certain genes play a role.

Some people with physical illness also experience depression, which may be caused by the disease itself, the stress of coping with the illness, or the medications that are used to treat the illness.

Other factors that may cause or contribute to depression include:

• Stress
• Abuse
• Homelessness
• Certain medications, including steroids and sleep aids
• Certain health conditions, including thyroid disease
• Alcohol or another substance use disorder

People with depression have mood changes and other symptoms that are present for at least two weeks. Some people experience more symptoms than others.

People may have some or a combination of the following feelings:

• Sadness
• Emptiness
• Hopelessness
• Anxiety
• Pessimism
• Frustration
  
• Irritability
• Anger
• Worthlessness
• Helplessness
• Guilt
• Restlessness

Depression also causes other symptoms, such as:

• Changes in appetite and eating habits—weight gain or weight loss are possible
• Changes in sleeping habits—more or less sleep than usual
• Trouble concentrating or remembering
• Difficulty learning new things
• Trouble making decisions
• Being overwhelmed by the prospect of completing simple chores, such as personal hygiene
• Lack of interest in activities that previously brought joy
• Low energy
• Fatigue
• A sensation of moving more slowly than usual
• Headaches, body aches, or digestive issues that have no known cause and that don’t resolve with treatment
• Thinking about death or suicide
• Attempts at suicide
  

People are more likely to experience depression if they:

• Have a personal or family history of depression
• Experience trauma or major stress
• Go through a significant life change, like getting divorced, being fired, or having a loved one die
• Experience loneliness or social isolation
• Have anxiety
• Have low self-esteem
• Are coping with a physical illness, such as cancer or a chronic health condition
• Take certain medications that may cause depression as a side effect
• Have alcohol use disorder or substance use disorder
• Have been diagnosed with attention-deficit/hyperactivity disorder (ADHD) or conduct disorder
• Are female
• Are an older adult

Your doctor may diagnose depression after speaking with you about your mood, your symptoms, and your personal or family history of depression. Doctors may also perform a physical exam and offer diagnostic tests to rule out other health conditions that may cause depression-like symptoms.

When asking about your personal medical history, you may also answer a series of questions designed to screen for depression. You should tell your doctor about your mood, as well as thoughts and behaviors, including any thoughts about death or suicide. You should tell your doctor if you drink alcohol or take drugs, or if there are changes in your eating and sleeping habits, stressors in your life, and if you’ve experienced trauma or a significant life change recently.

There are no physical signs to indicate that a person has depression. But during a physical exam, doctors may look for signs of other health conditions that they may suspect are causing your symptoms of depression.

Doctors may also send patients for blood or urine tests, to determine whether another health condition may be causing depressive symptoms.

A variety of treatments are available for depression. Even persistent cases of depression may be treated.

Doctors often recommend medication plus talk therapy. This combination treatment is often more effective than either treatment by itself. However, some people may benefit from medication or talk therapy alone.

Medication may help to alleviate symptoms by changing the chemical balance within the brain. Patients may need to wait one to two weeks after beginning medication therapy before noticing an effect. Different classes of prescription antidepressants are available, including:

• Selective serotonin reuptake inhibitors
• Serotonin-norepinephrine reuptake inhibitors
• Tricyclic antidepressants
• Monoamine oxidase inhibitors
• Serotonin modulators
• Atypical antidepressants

Talk therapy is also known as psychotherapy or counseling. A therapist may teach patients coping skills or help patients think about their problems differently. Different types of talk therapy are available, including:

• Cognitive behavioral therapy, during which patients learn how to change their behaviors or thought patterns, so they don’t become entrenched in thoughts or activities that may lead to depression
• Problem-solving therapy, during which a therapist helps a patient identify problems in their life that are linked to depression, then take concrete steps to improve the situation
• Psychodynamic therapy, during which a patient thinks back to childhood experiences and the ways that experience may influence present-day emotions or behaviors
• Interpersonal therapy, during which the therapist helps a patient examine relationships with friends or relatives to find ways to improve those interpersonal relationships, which may help to alleviate depression
• Couples/family therapy, during which a patient’s partner/relatives attend therapy, so that everyone may work together to address problems that are exacerbating the patient’s depression

Other treatments for depression may be effective when medication isn’t helpful, including:

• Electroconvulsive therapy. Patients receive anesthesia and muscle relaxants, then have electrodes attached to their heads. Doctors send a mild electric current through the electrodes to the brain, relieving symptoms.
• Transcranial magnetic stimulation. A strong electromagnetic coil is placed near the forehead, and electromagnetic pulses are sent through the coil. This helps to stimulate sections of the brain to improve symptoms.
• Vagus nerve stimulation. The vagus nerve connects to areas within the brain that affect mood. A small implanted device is used to send electrical impulses to the vagus nerve, which may relieve symptoms of depression.
• Ketamine or Esketamine. Doctors may use this intravenous medication, an anesthetic, to treat depression that doesn’t respond to antidepressants. Ketamine or esketamine may cause chemical changes in the brain that quickly alleviate symptoms, even in patients who have not responded to other treatments.

Doctors may also recommend lifestyle changes, such as:

• Getting more physical activity every day, which helps to lift mood
• Avoiding alcohol, which is a depressant
• Following a sleep schedule, aiming for 7 to 9 hours of rest, which may improve mood
• Spending time with people who care about you
• Doing activities that you find enjoyable

Talking about your feelings with friends or relatives

Most cases of depression are treatable, and symptoms should improve over time. Doctors may recommend that patients take antidepressants for several months.

Depression may not fully resolve in some people. It also may recur. Because suicidal thoughts and suicide are linked with depression, it’s important for people to stay engaged with their doctors to find an effective treatment.

“Yale is at the forefront of depression treatment,” says John Krystal, MD, chair of the Department of Psychiatry at the Yale School of Medicine. “We have exceptional clinical teams delivering cutting-edge of treatments, making Yale a national referral center for the treatment of mood disorders. Our work today builds on decades of Yale research on the neurobiology and treatment of depression, including innovations in psychotherapy and medications.”