What is major depressive disorder?

MDD is characterized by one or more depressive episodes, each lasting at least two weeks, during which five or more specific symptoms are present nearly every day. At least one of those symptoms must be either a persistently depressed mood or a marked loss of interest or pleasure in activities that were previously enjoyed.

The symptoms must represent a genuine change from how the person normally functions, cause significant distress or difficulty, and not be better explained by substance use, a medical condition, or another mental health condition such as bipolar disorder.

MDD is episodic for most people—there are periods of illness separated by periods of recovery. However, it tends to recur: with each episode, the risk of a future episode increases.

Common symptoms

A depressive episode requires five or more of the following symptoms, present nearly every day for at least two weeks, with at least one being depressed mood or loss of interest:

Depressed mood—persistent sadness, emptiness, or hopelessness most of the day; in children and adolescents, this may appear as irritability rather than sadness
Loss of interest or pleasure—a marked reduction in enjoyment of activities that used to feel rewarding (sometimes called anhedonia)
Changes in appetite or weight—significant weight loss or gain, or a noticeable decrease or increase in appetite
Sleep disturbance—difficulty falling or staying asleep, waking too early, or sleeping far more than usual
Psychomotor changes—moving or speaking noticeably more slowly, or feeling restless and agitated in a way others can observe
Fatigue—persistent low energy or exhaustion, even without physical exertion
Feelings of worthlessness or guilt—excessive self-criticism, shame, or guilt that is disproportionate to any actual situation
Difficulty thinking or concentrating—trouble focusing, making decisions, or remembering things
Thoughts of death or suicide—ranging from a passive wish not to wake up, to suicidal thoughts, planning, or attempts

How MDD can present differently

MDD can be specified with additional features that describe how an episode presents, which can guide treatment decisions:

With anxious distress

The episode is accompanied by prominent anxiety symptoms—feeling tense, unusually restless, worried about losing control, or fearful that something bad will happen.

With melancholic features

A particularly severe form characterized by a complete absence of pleasure, early morning wakening, the depression feeling worse in the morning, and significant psychomotor changes.

With atypical features

Mood can temporarily improve in response to positive events, often accompanied by increased sleep, increased appetite, a heavy feeling in the limbs, and sensitivity to rejection.

With peripartum onset

The episode begins during pregnancy or within four weeks of delivery. Often called postpartum depression when it occurs after birth, this is distinct from the brief "baby blues" that many new parents experience.

With seasonal pattern

Episodes occur regularly at the same time of year—most commonly in autumn or winter—and fully remit at other times. Sometimes called seasonal affective disorder (SAD).

With psychotic features

In severe cases, the depressive episode is accompanied by hallucinations or delusions, which may or may not be consistent with themes of depression such as guilt, worthlessness, or illness.

How common is it?

~7%

of U.S. adults affected in a given year

2x

more common in women than men

18–29

age group with the highest rates

MDD is one of the most prevalent mental health conditions worldwide. Prevalence varies globally and is elevated in contexts of inequality, discrimination, and socioeconomic disadvantage. In some cultures, depression more often presents through physical complaints—such as fatigue, headaches, or pain—than through openly expressed low mood.

When does it start and how does it progress?

MDD can begin at any age, but the peak age of onset is in the 20s. The course varies considerably between individuals. About 40% of people recover within three months of an episode, and around 80% recover within a year—with or without treatment. Treatment significantly shortens episodes and reduces the risk of recurrence.

MDD is often a recurrent condition. After a first episode, the risk of a second is around 60%. After two episodes, the risk of a third rises to around 70%, and so on. This pattern makes ongoing monitoring and, in some cases, maintenance treatment an important consideration.

Risk factors

Temperament and personality

People who tend toward negative thinking, emotional reactivity (neuroticism), or negative affectivity—a general tendency to experience negative emotions—are at higher risk of developing MDD.

Life experiences

Childhood trauma, socioeconomic adversity, and experiences of discrimination or inequality are associated with significantly higher rates of depression. Stressful life events often trigger episodes in people who are already vulnerable.

Genetics

MDD is 2 to 4 times more common in first-degree relatives of people with the condition. Around 40% of the risk is estimated to be inherited, with the remaining risk coming from environmental factors and their interaction with genes.

Major depression and suicidal thoughts

MDD is strongly associated with suicide. Key risk factors include previous attempts, feelings of hopelessness, sleep disturbance, impulsivity, and access to lethal means. If you or someone you know is struggling with thoughts of suicide or self-harm, please reach out for help immediately.

988 Suicide & Crisis Lifeline: Call or text 988 (available 24/7 in the U.S.)

Conditions that often occur alongside MDD

MDD commonly co-occurs with:

Anxiety disorders
Panic disorder
Post-traumatic stress disorder (PTSD)
Obsessive-compulsive disorder (OCD)
Substance use disorders
Eating disorders
Borderline personality disorder

Co-occurring conditions are common and can complicate both diagnosis and treatment. A thorough assessment takes the full picture into account.

What to do next

MDD is highly treatable—most people see significant improvement with the right support. The most effective approaches include cognitive behavioral therapy (CBT), which targets the thought patterns and behaviors that sustain depression; antidepressant medication, particularly SSRIs and SNRIs; and a combination of both, which tends to produce the best outcomes for moderate to severe depression.

Other evidence-based approaches include behavioral activation (gradually reintroducing rewarding activities), interpersonal therapy (IPT), and for severe or treatment-resistant cases, options such as electroconvulsive therapy (ECT) or newer treatments like ketamine.

If low mood, loss of interest, or other symptoms have been present for more than two weeks and are affecting your daily life, speaking with a GP or mental health professional is a good first step. Early support leads to faster recovery.