What is major depressive disorder?

Major depressive disorder¹, also referred to as depression or clinical depression, is a common but serious mood disorder.

Depression is different from normal sadness or anger that comes and goes. It can cause severe symptoms, including persistent sadness, fatigue, and a loss of interest in things you usually enjoy. These symptoms can affect how you think, feel, and manage everyday life. You may even begin to feel that life isn’t worth living.

Depression isn’t a weakness. It isn’t something someone can just “snap out of,” either. In many cases, depression requires long-term treatment. The good news, however, is that treatment (with medication, psychotherapy, or a combination of the two) can help you manage and improve the symptoms of depression.

How common is depression?

Depression is one of the most common² mental health disorders in the United States. Roughly 264 million people³ live with depression worldwide, and an estimated 17.3 million⁴ U.S. adults (7.1%) have experienced at least one major depressive episode.

Depression can occur at any age, but it frequently begins in adulthood—the median age of onset is 32.5 years old3. Depression is also more common in women than in men4.

What causes depression?

Researchers aren’t exactly sure what causes⁵ depression. As is the case with many mental disorders, a number of factors may contribute to depression, including:

• Brain chemistry: Naturally occurring brain chemicals called neurotransmitters likely play a role in depression. Recent research indicates that changes in neurotransmitters and how they interact with neurocircuits that help maintain mood stability may play a role in the development and treatment of depression.
• Biological differences: People with depression appear to have changes⁶ in the areas of the brain that control mood. This can be due to poor nerve cell function. Communication between nerve cells or circuits can make it more difficult for an individual to regulate their moods.

• Hormonal changes: Changes in the body’s hormonal balance can have a negative impact on mood, triggering depression. These changes can occur in pregnancy and during the weeks or months following delivery (called postpartum depression), as well as in thyroid problems, menopause, and numerous other conditions.
• Genetics: If you have a blood relative with depression, you’re more likely to develop the condition yourself, as well as problems with alcohol⁷. Researchers are working to identify the genes involved in causing depression. Episodes of depression may also be triggered by stressful life events. In most cases, however, depression doesn’t seem to be related to one particular event.

Risk factors for depression

Some factors⁸ may increase your risk of developing depression, including:

• Biological sex: More women are diagnosed with depression than men. This may be partially due to women seeking treatment more frequently.
• Certain personality traits or “temperament,” such as low self-esteem, dependence on others, or being highly self-critical or pessimistic.
• Family history: Having blood relatives with a history of depression, bipolar disorder, alcoholism, or suicide increases your risk of depression.
• Being lesbian, gay, bisexual, transgender, intersex (being born with variations in the development of genital organs that aren’t clearly biologically male or female) or any part of the LGBTQIA+ community without receiving adequate emotional support
• History of other mental health disorders, including anxiety disorders, eating disorders, or post-traumatic stress disorder (PTSD)
• Excess use or abuse of alcohol or drugs
• Serious chronic illness, including cancer, chronic pain, stroke, or heart disease
• Certain medications, such as sleeping pills or some high blood pressure medications

Symptoms of depression

For some people, depression only occurs once in their lifetimes. Generally, however, people with depression experience multiple episodes. During these episodes, the symptoms of depression occur throughout most of the day, nearly every day.

On average, untreated episodes can last for several months. However, episodes of major depression can last for any length of time. Thy signs and symptoms of depression can vary from mild to severe throughout the course of an episode.

Common signs and symptoms⁹ of major depressive disorder include:

• Sadness and tearfulness
• Feelings of emptiness or hopelessness
• Loss of interest or pleasure in many or all activities, including hobbies, sports or exercise, and sex
• Irritability, frustration, or angry outbursts, even over small issues
• Sleep disturbances, including insomnia or sleeping too much
• Weight gain or loss
• Increased or decreased appetite
• Anxiety or restlessness
• Slowed thinking, speech, or movement
• Unexplained physical problems, such as headaches or back pain
• Fatigue and lack of energy, causing even small tasks to require extra effort
• Trouble thinking, concentrating, making decisions, or remembering things
• Feelings of worthlessness or guilt
• Fixating on past failures, self-criticism, or self-blame
• Frequent thoughts of death, suicidal thoughts, suicide plans or attempts

For many people living with depression, symptoms can be severe enough to interfere with daily life and activities, such as school, work, social interactions, or personal relationships.

Some people may feel generally miserable, detached, or exhausted. They may feel worthless and guilty, either about specific experiences or not related to anything in particular. When emotional pain, guilt, and self-criticism become severe, they can lead to self-destructive behaviors or thoughts of death and suicide.

While the vast majority of people with depression do not attempt or commit suicide, they are more likely to do so¹⁰ than people without depression.

Major depressive episodes can cause a person to have pessimistic thoughts and ideas that may be out of proportion with reality. In some cases, depressed thinking becomes distorted enough to be called “psychotic.”

When this occurs, the person may have considerable difficulty recognizing reality. They may develop delusions (false beliefs) or hallucinations (false perceptions).

Some people who experience periods of major depression also go through episodes of abnormally high energy or irritability. When severe, this is referred to as “mania” or a manic episode. People going through manic episodes present psychotic symptoms. They may sleep far less than normal and conceive grand plans that could never realistically be carried out. When a person has mild manic symptoms and doesn’t lose touch with reality, it’s referred to as “hypomania” or a hypomanic episode.

When untreated, depression can become chronic (long-lasting). People who have had many depressive episodes may experience periods of persistent but milder symptoms.

If you suspect that you may have depression, talk to your healthcare provider. Effective treatment can help shorten the length and severity of depressive episodes.

Types of depression

There are multiple types¹¹ of depression. They may develop under different circumstances or present with slightly different symptoms.

Your provider or specialist may add one or more specifiers to clarify the type of depression you have. Specifiers indicate that you have depression with specific features, and may include:

• Anxious distress: Depression that causes unusual restlessness, anxiety, or worry about possible events or loss of control
• Melancholic features: Severe depression that causes a lack of response to things that used to bring pleasure. This can cause problems with early morning awakening, worsened mood in the morning, drastic appetite changes, and feelings of agitation, sluggishness, or guilt
• Mixed features: Simultaneous depression and mania, which may present with elevated self-esteem, talking excessively, and increased energy
• Atypical features: Depression characterized by the ability to temporarily be cheered up by positive events, increased appetite, excessive need for sleep, sensitivity to rejection, and a feeling of heaviness in the arms or legs
• Psychotic features: Depression accompanied by delusions or hallucinations, which may revolve around personal inadequacy or other negative themes
• Catatonia: Depression that includes motor activity, causing either uncontrollable, purposeless movement or fixed, inflexible posture
• Seasonal pattern: Also called seasonal affective disorder (SAD). Depression related to changes in seasons and reduced exposure to sunlight that typically occurs in the winter months
• Peripartum onset: Depression that occurs during pregnancy or begins weeks or months following delivery (postpartum depression)

Depression in children and teenagers

The common signs and symptoms¹² of depression in children and teens are similar to those seen in adults. However, there can be some differences.

Symptoms of depression in younger children can include:

• Sadness
• Irritability
• Anxiety or worry
• Aches and pains
• Refusing to go to school or social activities
• Being underweight

Symptoms of depression in teenagers can include:

• Sadness
• Irritability
• Feelings of negativity or worthlessness
• Anger
• Poor school performance or attendance
• Feeling misunderstood and extremely sensitive
• Eating or sleeping too much
• Self-harm
• Loss of interest in normal activities
• Avoidance of social interaction or isolation

Depression symptoms in older adults

Depression is not a normal part of growing older and should not be overlooked. However, older adults may feel reluctant to seek help for depression, causing the condition to frequently go undiagnosed and untreated.

The symptoms¹³ of depression in older adults may be different or less obvious, and can include:

• Physical aches or pain
• Memory difficulties
• Changes in personality
• Fatigue, loss of appetite, sleep problems, or loss of interest in sex not caused by medical conditions or medication
• Frequently wanting to stay at home, rather than socializing or trying new activities
• Suicidal thoughts or feelings, especially in older men

If you or a loved one shows any of these signs or symptoms, speak to a healthcare provider. They will be able to properly diagnose and treat depression.

Complications from depression

Depression is a serious condition. It can take a considerable toll on those living with the disorder and their close family and friends.

When untreated, depression often worsens, resulting in emotional, behavioral, and health problems that can significantly impact all areas of life.

Some complications¹⁴ associated with depression include:

• Excess weight or obesity (which can lead to diabetes and heart disease)
• Pain or physical illness
• Anxiety, panic disorder or panic attacks, or social phobia
• Alcohol or drug abuse
• Strained personal relationships
• Problems or declined performance in work or school
• Self-harm, such as cutting
• Suicidal thoughts or feelings, suicide attempts, or suicide
• Premature death due to medical conditions

The best way to prevent these complications from occurring is to seek medical treatment. Depression is a serious condition, and you don’t have to deal with it alone.