What Is Depression?

Depression is a mood disorder that causes symptoms affecting feelings, thoughts, and daily functioning. It is one of the most common mental health conditions in the United States, and it can have severe and lasting effects.

Major depressive disorder is diagnosed after someone experiences two weeks of a specific number of symptoms combined with depressed mood or loss of interest.

In 2019, approximately 19.4 million adults in the United States had at least one major depressive episode, which was about 7.8% of the adult population. Among adolescents, an estimated 3.8 million people aged 12–17 years in the United States had at least one major depressive episode in 2019, which was about 15.7% of that population.

Causes

Research has shown that there is not one single cause of depression, but, rather, it is a combination of psychological, genetic, biological, and environmental contributing factors. It often begins in adulthood, but it is seen in children and adolescents as well, often appearing differently in these age groups than in adults. Especially in adults, depression can be comorbid (co-occurring) with other medical illnesses, like diabetes, heart disease, cancer, and Parkinson’s disease.

Some risk factors for depression include:

Personal history of depression Family history of depressionSignificant life changes Traumatic eventsChronic stressSpecific physical illnesses and medications

Signs and Symptoms

Depression can impact many aspects of life with a variety of signs and symptoms. However, every individual does not experience all the symptoms, and some people may experience additional symptoms. Typically, symptoms are experienced most of the day, almost every day, for at least two weeks.

Some people may also experience other physical symptoms of aches or pains, headaches, or digestive issues that are unexplained and do not ease with treatment. Every individual experience is different, so severity, frequency, and the length of time symptoms last will vary from person to person.

Persistent sad or depressed mood  Hopelessness Irritability  Feelings of guilt or worthlessness Anhedonia (loss of interest or enjoyment in hobbies and activities) Fatigue or decrease in energy  Talking or moving slower than usual Restlessness or trouble sitting still Difficulty concentrating Difficulty sleeping or sleeping too much  Decrease (or increase) in appetite or weight changes  Thoughts of death or suicide

Types

There are several different types of depression, which vary in timing and symptoms. The most common ones are:

Major depressive disorder (MDD): This causes a depressed mood or loss of interest combined with other symptoms that last for at least two weeks.   Psychotic depression: This is depression that occurs with psychotic symptoms, like delusions (fixed, false beliefs) or hallucinations (typically seeing or hearing things that others do not see or hear).   Persistent depressive disorder: Also called dysthymia, this leads to at least two years of depressive symptoms, sometimes with major depressive episodes occurring along with periods of less-severe symptoms.    Peripartum depression: This diagnosis is when depression occurs during or after pregnancy (postpartum).    Seasonal affective disorder (SAD): This is depression occurring seasonally, typically during the winter months, when there is less sunlight.   Bipolar disorder: This is not specifically a depressive disorder, but bipolar disorder does include episodes of major depression along with periods of mania, which is an extremely elevated or euphoric mood, or hypomania, a less severe form.

Screening and Diagnosis

If you are experiencing symptoms of depression, it is important to speak with your healthcare provider or other healthcare professional. Your medical doctor will perform a physical exam, take a history and obtain lab tests to determine if there may be a medical contribution to your symptoms. Once this is ruled out, they will possibly refer you to a mental health professional for further treatment, like a psychiatrist, psychologist, or therapist.

Screening for depression in a primary care setting usually is done using the Patient Health Questionnaire (PHQ-2 or PHQ-9), a diagnostic tool for mental health conditions. Many family medicine practices use a two-step screening process, first with the two-question PHQ followed by the PHQ-9 if the first questionnaire points to positive signs.

The diagnostic criteria for major depressive disorder are from the most recent, fifth edition of the “Diagnostic and Statistical Manual for Mental Disorders” (DSM-5), the authority used by mental health professionals to diagnose psychiatric conditions. Depression is diagnosed when someone has at least five symptoms all day and nearly every day for at least two weeks. One of these symptoms needs to be a depressed mood or loss of interest in activities. However, for children and adolescents, the mood might be irritability instead.

Over the last two weeks, how often have you been bothered by any of the following problems?

Little interest or pleasure in doing thingsFeeling down, depressed, or hopelessTrouble falling or staying asleep, or sleeping too muchFeeling tired or having little energyPoor appetite or overeatingFeeling bad about yourself—or that you are a failure or have let yourself or your family downTrouble concentrating on things, such as reading the newspaper or watching televisionMoving or speaking so slowly that other people could have noticed—or the opposite, being so fidgety or restless that you have been moving around a lot more than usualThoughts that you would be better off dead or of hurting yourself in some way

If you checked off any problems, how difficult have these problems made it for you to do your work, take care of things at home, or get along with other people?

Prevention of Depression

Nonmedical interventions that can help improve mood include:

Physical activity, even 30 minutes of walking Regular bedtime and wake-up times Eating regular and healthy meals Prioritizing tasks, doing what is needed when you canConnecting with other peopleTalking with trusted people about how you feel Avoiding alcohol, tobacco, and other drugs

When to Seek Professional Help

If someone notices symptoms of depression in themselves or a loved one and it is affecting their daily life and functioning, it is important to seek professional help from a healthcare provider, such as a primary care provider, psychiatrist, or psychologist. They will be able to provide resources, appropriately diagnose, and provide treatment if necessary.

A Word From Verywell

Depression is a serious illness that can greatly impact your life and functioning. If you are concerned about yourself or a loved one, it is important to seek help from a qualified healthcare provider. Sometimes it is difficult to make that first step to seek help, so look to trusted friends and family for support and encouragement or provide that yourself to someone you are concerned about. With appropriate diagnosis and treatment, you can work toward feeling better and regaining your life.

If you are having suicidal thoughts, dial 988 to contact the 988 Suicide & Crisis Lifeline and connect with a trained counselor. If you or a loved one are in immediate danger, call 911.

For more mental health resources, see our National Helpline Database.