Depression

Understanding Depression

What Is Depression?

Depression, known clinically as major depressive disorder, is a common mood disorder in which a person experiences persistent low mood or loss of interest and pleasure for at least two weeks, along with other symptoms such as changes in sleep and appetite, fatigue, poor concentration and feelings of worthlessness, that significantly affect daily life. It is different from ordinary sadness and is not a sign of weakness or a character flaw.

Depression affects the whole person: thoughts, feelings, behavior and physical health. The World Health Organization estimates that around 280 million people worldwide live with depression, and it is a leading cause of disability. In the US, a large national survey published in 2018 found that about 21% of adults meet criteria for major depression at some point in their lives. Depression is also highly treatable, and most people who receive appropriate care improve.

The Depression Experience

People describe depression in many ways: living under a heavy gray cloud, feeling numb or empty, being cut off from others, or losing the ability to feel pleasure in things that used to matter. Everyday tasks, such as showering, answering messages or getting to work, can feel exhausting. Many people also experience physical symptoms, including aches, digestive problems and changes in appetite.

Depression vs. Sadness

Grief after a loss can resemble depression, and the two can overlap. The DSM-5-TR asks clinicians to use judgment in distinguishing normal grief from a depressive episode; see grief and loss.

The Biology of Depression

Depression involves changes in brain function, stress hormones and the immune system, but no single biological cause has been found.

• Neurotransmitters: serotonin, norepinephrine, dopamine and glutamate are involved in regulating mood and are targets of some treatments. However, the popular "chemical imbalance" explanation is an oversimplification; a 2022 umbrella review found no consistent evidence that low serotonin causes depression.
• Brain networks: imaging studies show average differences in networks involving the prefrontal cortex, amygdala and hippocampus, which help regulate emotion, reward and memory.
• Stress systems: chronic stress can alter the HPA axis, the body's hormonal stress system, and elevated cortisol is found in some people with depression.
• Inflammation: inflammatory markers are raised in a subset of people with depression, an active area of research.

Our page on the neuroscience of behavior covers these systems in more depth.

Types of Depression

Major Depressive Disorder (MDD)

The most common form, involving one or more episodes of at least two weeks with significant symptoms. Episodes may be single or recurrent, and severity ranges from mild to severe.

Persistent Depressive Disorder (Dysthymia)

Persistent depressive disorder involves depressed mood on most days for at least two years in adults (one year in children and adolescents). Symptoms may be milder than in major depression, but their persistence can make people feel depression is simply who they are.

Bipolar Depression

Depression can also occur as part of bipolar disorder, alternating with periods of mania or hypomania. Distinguishing bipolar from unipolar depression is important because treatment approaches differ.

Seasonal Affective Disorder (SAD)

In the DSM-5-TR, this is described as depression "with seasonal pattern." Episodes typically begin in autumn or winter and lift in spring, linked to reduced daylight and changes in circadian rhythms. Oversleeping, increased appetite and carbohydrate craving are common. Light therapy, used under clinical guidance, has research support.

Postpartum (Peripartum) Depression

The DSM-5-TR uses the specifier "with peripartum onset" for depression beginning during pregnancy or within four weeks after delivery, although many clinicians consider the first year after birth. It goes beyond the common, short-lived "baby blues" and affects an estimated 10–15% of new mothers. See postpartum depression.

Premenstrual Dysphoric Disorder (PMDD)

PMDD involves marked mood symptoms, such as irritability, depressed mood and anxiety, in the week before menstruation that improve after it starts. The DSM-5-TR estimates its 12-month prevalence at about 1.8–5.8% of people who menstruate.

Atypical Features

Depression "with atypical features" involves mood that brightens in response to positive events plus symptoms such as increased appetite, oversleeping, heavy limbs and strong sensitivity to rejection. Despite the name, it is common.

Psychotic Features

In severe depression, some people experience delusions or hallucinations, usually related to themes of guilt, illness or worthlessness. This requires prompt specialist care.

Symptoms and Signs

The DSM-5-TR lists nine symptoms of a major depressive episode. Clinicians look for five or more, present most of the day nearly every day for at least two weeks, including at least one of the first two:

1. Depressed mood (in children and teens, this may appear as irritability).
2. Markedly diminished interest or pleasure in activities (anhedonia).
3. Significant weight or appetite change.
4. Sleeping too little or too much.
5. Restlessness or slowed movement noticeable to others.
6. Fatigue or loss of energy.
7. Feelings of worthlessness or excessive guilt.
8. Difficulty thinking, concentrating or making decisions.
9. Recurrent thoughts of death or suicide.

These symptoms must cause significant distress or impairment and not be better explained by a substance, a medical condition or another disorder. This list is descriptive; only a qualified professional can make a diagnosis.

Emotional and Cognitive Symptoms

Beyond low mood, people may feel hopeless, irritable, anxious or numb. Thinking often becomes more negative and self-critical, and rumination, repetitive dwelling on problems and failures, is common. Concentration and memory can suffer.

Physical Symptoms

Fatigue, sleep changes, appetite changes, aches and pains, digestive problems and reduced sex drive are common. In some cultures and in older adults, physical symptoms may be more prominent than reported sadness.

Behavioral Symptoms

Withdrawal from friends and activities, reduced productivity, neglect of self-care, and increased use of alcohol or other substances can all be signs of depression.

Depression and Suicide Risk

Depression is one of the strongest risk factors for suicide. Thoughts that life is not worth living, or that others would be better off without you, are symptoms of the illness and deserve to be taken seriously. If you or someone you know is having thoughts of suicide, please reach out now; our crisis resources page lists services that can help immediately.

Causes and Risk Factors

Depression usually results from several interacting factors rather than a single cause. Psychologists often use a diathesis-stress model: an underlying vulnerability is triggered by stressful experiences.

Biological Factors

• Genetics: twin studies estimate heritability of major depression at roughly 30–40%. Many genes of small effect contribute.
• Medical conditions: chronic illness, chronic pain, thyroid disorders and neurological conditions raise risk.
• Hormonal changes: such as those around childbirth, the menstrual cycle and perimenopause.
• Substances and medicines: alcohol, some drugs and certain medications can contribute.

Psychological Factors

• Negative thinking patterns: Aaron Beck's cognitive theory describes a "cognitive triad" of negative views of the self, the world and the future.
• Learned helplessness: Martin Seligman's research suggested that repeated uncontrollable stress can lead to passivity and hopelessness.
• Personality: high neuroticism, perfectionism and low self-esteem increase vulnerability.
• Early experiences: childhood adversity, abuse and neglect are linked to higher lifetime risk.

Environmental and Social Factors

• Stressful life events such as bereavement, divorce, job loss or financial stress.
• Chronic stress, including caregiving, discrimination and poverty.
• Loneliness and lack of social support.
• Trauma and violence.

Protective factors include supportive relationships, physical activity, meaningful activity and coping skills.

Depression and Anxiety Screening Tools

Because depression and anxiety are common and often missed, many health systems use brief questionnaires to identify people who may need further assessment. The US Preventive Services Task Force recommends screening adults for depression and, for adults under 65, for anxiety. These tools are designed to screen, not to diagnose: a high score means a conversation with a qualified clinician is warranted.

Suicide risk screening

Clinicians also use structured questions to ask about suicidal thoughts, often prompted by the PHQ-9's final item. Tools such as the Columbia Suicide Severity Rating Scale and the Ask Suicide-Screening Questions (ASQ), developed with the US National Institute of Mental Health, guide a careful, compassionate conversation and help clinicians decide what support is needed. Asking about suicide does not increase risk; research shows it can be a relief and opens the door to help.

Limits of screening tools

• They capture symptoms over a short period and can be affected by temporary stress.
• They cannot distinguish between causes, such as depression versus bipolar disorder, grief or a medical condition.
• Cultural and language differences can affect how questions are understood.
• Online versions completed alone offer no follow-up; results should be discussed with a professional.

For more on how screening works, see our guide to mental health screening.

Diagnosis and Assessment

Clinical Assessment

A doctor, psychologist or psychiatrist diagnoses depression through a clinical interview covering current symptoms, their duration and impact, previous episodes, any periods of elevated mood, family history, substance use, medical conditions and current stressors. Screening questionnaires often support this process.

Differential Diagnosis

• Bipolar disorder: a history of mania or hypomania changes the diagnosis and treatment approach.
• Adjustment disorder: distress linked to a specific stressor that does not meet full depression criteria. See adjustment disorders.
• Grief: normal bereavement or prolonged grief disorder.
• Anxiety disorders: which frequently co-occur. See anxiety vs. depression.
• Substance-induced or medical causes: such as hypothyroidism, anemia or medication side effects.

Medical Evaluation

Doctors may order blood tests to check for thyroid problems, anemia, vitamin deficiencies or other physical causes of fatigue and low mood, and review current medicines.

Treatment Options

Treatment Overview

Effective treatments for depression include psychological therapies, medication, and in some cases other medical treatments. Clinical guidelines, such as those from the UK's National Institute for Health and Care Excellence and the American Psychological Association, recommend matching treatment to severity, history and personal preference.

Stepped Care Approach

1. Mild symptoms: guided self-help based on CBT, physical activity programs, group therapy or brief psychological interventions.
2. Moderate to severe symptoms: individual psychotherapy, medication, or a combination.
3. Severe, persistent or complex depression: specialist mental health services, combined treatment and, for some, other medical treatments.

Treatment Settings

Most people are treated in primary care or outpatient settings, including online therapy. Intensive outpatient programs and, for severe illness or high risk, hospital care are also available.

Psychotherapy Approaches

Meta-analyses by Pim Cuijpers and colleagues show that several structured psychotherapies have similar, meaningful effects for adult depression, and that combining therapy with medication is often more effective than either alone for moderate to severe depression.

Cognitive Behavioral Therapy (CBT)

CBT helps people identify and test negative thoughts, reduce avoidance and build coping skills. It is among the most researched treatments for depression, and its benefits tend to persist after therapy ends.

Behavioral Activation

Behavioral activation focuses on gradually re-engaging with rewarding and meaningful activities. A large 2016 UK trial (COBRA) found it as effective as CBT and cheaper to deliver.

Interpersonal Therapy (IPT)

Interpersonal therapy, developed by Gerald Klerman and Myrna Weissman, addresses relationship problems, role transitions, grief and conflicts linked to depression.

Psychodynamic Therapy

Short-term psychodynamic therapy explores patterns from past relationships and unconscious conflicts and has research support for depression.

Mindfulness-Based Therapies

Mindfulness-based cognitive therapy (MBCT) was designed to prevent relapse in people with recurrent depression, and trials show it reduces relapse risk, particularly for those with three or more previous episodes.

Medication

Antidepressant medication is one option a doctor or psychiatrist may discuss, particularly for moderate to severe depression, recurrent depression, or when therapy alone has not helped enough. Several classes of antidepressants exist, with different side-effect profiles. Research shows they help many people, with benefits typically building over several weeks; their advantage over placebo is clearer in more severe depression.

A few general points from the research are worth knowing:

• Finding the right treatment can take time, and some people try more than one approach.
• Doctors usually recommend continuing treatment for some months after recovery, because stopping early increases relapse risk.
• Stopping antidepressants suddenly can cause withdrawal (discontinuation) symptoms, so any change should be planned with the prescriber.
• Young people starting antidepressants are monitored closely, as regulators have warned of a possible increase in suicidal thoughts in some under-25s early in treatment.

Decisions about medication, including whether to use it, which kind and for how long, belong with a prescribing clinician who knows the person's history.

Other Medical Treatments

For severe or treatment-resistant depression, psychiatrists may discuss other options, such as electroconvulsive therapy, which has strong evidence in severe depression, transcranial magnetic stimulation, or newer rapid-acting treatments delivered under medical supervision. These are specialist decisions made with informed consent.

Living with Depression

Self-Care Strategies

Alongside professional care, research supports several everyday habits for wellbeing and recovery. These do not replace treatment, but they can help:

• Physical activity: meta-analyses show regular exercise reduces depressive symptoms, with effects comparable to other treatments in some studies. See exercise psychology.
• Sleep: regular sleep and wake times support mood. See sleep hygiene.
• Activity scheduling: planning small, achievable, enjoyable or meaningful activities each day.
• Limiting alcohol: alcohol is a depressant and can worsen mood and sleep.
• Self-compassion: treating oneself with the kindness one would show a friend. See self-compassion.

Building Support Systems

Staying connected, even briefly, helps. Telling a trusted person what is happening, joining a support group, or reconnecting with community activities can reduce isolation. Family and friends can find guidance in our article on how to support someone.

Managing Daily Life

Breaking tasks into small steps, lowering expectations temporarily, and asking for practical help can make daily life more manageable. Workplace adjustments, such as flexible hours, may be available.

Crisis Management

A personal safety plan, made with a clinician, lists warning signs, coping strategies, people to contact and professional services. If thoughts of suicide become strong, contact emergency services or a crisis line immediately; see our crisis resources.

Recovery and Prevention

Recovery Process

Recovery is often gradual, with good and bad days. Many people notice improvements in sleep and energy before mood lifts. Recovery means a return to meaningful life, not never feeling low again.

Relapse Prevention

Depression can recur, and the risk rises with each episode. Strategies that lower relapse risk include continuing treatment as recommended, MBCT or booster therapy sessions, recognizing early warning signs, and maintaining helpful routines.

Building Resilience

Supportive relationships, regular physical activity, purpose and flexible coping skills are associated with lower risk of depression. See resilience building.

Long-Term Outlook

With treatment, most people with depression improve substantially, and many recover fully. Some experience recurrent or chronic depression and benefit from longer-term care. Early help leads to better outcomes.

Conclusion

Depression is a common, serious and treatable condition that affects mood, thinking, the body and relationships. It arises from a mix of biological, psychological and social factors rather than personal weakness. Brief screening tools such as the PHQ-9 and GAD-7 help identify people who may need support, and effective treatments, including psychotherapy and medication a doctor may discuss, help many people recover. If low mood has lasted more than two weeks or is affecting daily life, speaking with a primary care doctor or licensed therapist is a valuable first step.