Major depressive disorder is what most people picture when they hear the word depression. It is also the most studied. After decades of research and several updates to the clinical criteria, the picture is clearer than the public conversation usually suggests. The condition is common, the criteria are specific, and the outcomes with adequate treatment are generally good.
This page covers what it is, who it affects, how it sits in the wider picture of depressive disorders, how clinicians sort it out, what current treatment looks like, what happens when the first treatment does not work, and what living with the condition usually looks like over time.
Quick view
- A defined two-week pattern, not a passing feeling.
- About 8.4 percent of U.S. adults have it in any given year. Lifetime prevalence is near 21 percent.
- First-line treatments are psychotherapy, antidepressants, or a combination.
- Most people respond, though the first medication tried is not always the right one. With sequential adjustments, about two thirds of patients reach remission (STAR*D).
What it is
A major depressive episode in the DSM-5-TR requires five or more of the following nine symptoms during the same two-week period, with at least one being depressed mood or loss of interest. The symptoms must represent a clear change from the person's baseline, last most of the day nearly every day, and have a meaningful effect on work, school, or relationships, and there has been no manic or hypomanic episode. A history of mania or hypomania changes the diagnosis to bipolar disorder, which is treated differently.
- Depressed mood most of the day, nearly every day.
- Loss of interest or pleasure in nearly all activities.
- Significant weight loss, weight gain, or appetite change.
- Insomnia or hypersomnia.
- Observable agitation or slowing of movement.
- Fatigue or loss of energy.
- Feelings of worthlessness or excessive guilt.
- Reduced ability to think, concentrate, or make decisions.
- Recurrent thoughts of death or suicide.
A diagnosis of major depressive disorder is made when a person has had at least one episode and the episode is not better explained by bipolar disorder, another psychiatric condition, a medical condition, or a substance. Episodes are also assigned specifiers (mild, moderate, severe; with anxious distress; with melancholic features; with atypical features; with psychotic features; with peripartum onset; with seasonal pattern). These specifiers do not change the diagnosis but do affect treatment choices.
Where it sits in the wider picture
Several conditions live near major depressive disorder. Persistent depressive disorder is a chronic, lower-intensity pattern lasting at least two years. Premenstrual dysphoric disorder is a cyclic mood disturbance linked to the menstrual cycle. Disruptive mood dysregulation disorder is a childhood pattern. Adjustment disorder with depressed mood follows a clear stressor and is shorter and less severe. Bipolar disorder includes depressive episodes but also includes mania or hypomania, which changes the treatment plan.
Sorting these out is the first job of an evaluation.
Who it affects
About 21 million U.S. adults had a major depressive episode in 2021. Lifetime prevalence is near 21 percent. Women are affected at roughly twice the rate of men. The median age of first onset is in the mid-20s, though depression can begin in childhood, in adolescence, in middle age, or for the first time in older adulthood.
Risk factors include a family history of depression, a prior depressive episode, chronic medical illness, chronic stress, exposure to trauma, social isolation, substance use, certain medications (steroids, interferon, some hormonal contraceptives in vulnerable people), and certain life transitions (postpartum period, retirement, prolonged grief).
What an episode can look like in real life
A person who used to enjoy work struggles to start anything for weeks. Sleep is fragmented or excessive. Food has no appeal, or it becomes constant. The mind cycles through old failures and current shortcomings. Friends do not hear back. Showers slip to twice a week. The person describes feeling empty, slow, or stuck, and often cannot point to a single trigger.
In some people, the presentation is irritability rather than sadness. In some older adults, the presentation is cognitive slowing, fatigue, and physical complaints that read like a medical illness until depression is asked about directly. In some adolescents, the presentation is boredom that does not lift, withdrawal from friends, and a drop in school performance.
How clinicians sort it out
A first evaluation usually takes 45 to 60 minutes and covers:
- Current symptoms in detail (duration, severity, effect on function).
- Past episodes, including any that were not treated.
- Any history of mania or hypomania, even brief, including any periods of decreased need for sleep, racing thoughts, faster or pressured speech, increased goal-directed activity, or risky decisions. A yes here points to bipolar disorder.
- Family psychiatric history.
- Medical history, including thyroid disease, sleep apnea, anemia, vitamin deficiencies, chronic pain, neurologic disease.
- Current medications, including steroids, interferon, and any medication that can lower mood.
- Substance use, including alcohol, cannabis, and stimulants.
- Trauma history.
- Safety, including suicidal thoughts, intent, plan, and access to means.
Screening tools used in everyday practice include the PHQ-9 (depression severity), the GAD-7 (anxiety severity), the MDQ (screen for bipolar disorder), and the C-SSRS (suicidality). A score is a starting point, not a diagnosis.
Laboratory workup usually includes thyroid function tests at minimum, with vitamin B12, vitamin D, and a complete blood count added based on the picture.
Treatment
First-line treatment includes psychotherapy with strong evidence, first-line antidepressants, or a combination. For mild to moderate depression, either is appropriate. For moderate to severe depression, combination treatment usually produces better outcomes than either alone.
Psychotherapies with strong evidence in MDD. Cognitive behavioral therapy. Behavioral activation. Interpersonal therapy. Problem-solving therapy. Mindfulness-based cognitive therapy (often used after recovery, for relapse prevention).
First-line antidepressants. SSRIs (sertraline, escitalopram, fluoxetine, paroxetine, citalopram). SNRIs (venlafaxine, duloxetine, desvenlafaxine). Bupropion. Mirtazapine in selected cases. The choice depends on the side effect profile, other conditions, prior medication history, and patient preference.
What to expect on timing. Most people start to notice changes in two to six weeks, with sleep, appetite, and energy often shifting before mood does. Full benefit often takes eight to twelve weeks. The first medication tried is not always the right one. About one in three people reach remission on the first medication tried, and roughly half show a meaningful response (STAR*D). Most patients need a change in dose, a switch, or an addition.
What if the first treatment does not help. The most important next step is to re-check the diagnosis and the prior trial. Was the dose adequate? Was the duration adequate? Is there a missed bipolar history? Is there an untreated medical contributor or active substance use? From there, options include increasing the dose, switching class, adding a second agent, adding therapy, or moving to specific options for treatment-resistant depression.
Treatment-resistant depression
When two adequate trials of standard antidepressants have not produced response, the term treatment-resistant depression often applies. Options at this point include lithium or T3 augmentation, atypical antipsychotic augmentation (aripiprazole, brexpiprazole, quetiapine, olanzapine-fluoxetine combination), esketamine (FDA approved nasal spray), ketamine (off-label intravenous), transcranial magnetic stimulation (FDA approved), and, in severe or life-threatening cases, electroconvulsive therapy. Each has its own risks, evidence base, and access requirements.
Special populations
- Pregnancy and postpartum. Treatment is individualized. Many SSRIs are considered compatible. Brexanolone and zuranolone are newer agents specifically indicated for postpartum depression. Untreated depression in pregnancy carries its own risks and is not a safe default.
- Adolescents. Fluoxetine and escitalopram are first-line antidepressants with FDA indications in this age group. Therapy is a key part of the plan. Suicidal thoughts are tracked closely after starting medication.
- Older adults. Side effect profiles, falls risk, drug interactions, and cognitive symptoms shape choices. SSRIs are usually first-line.
- Co-occurring anxiety. A substantial share of patients with MDD also have co-occurring anxiety (roughly 50 to 60 percent in clinical samples; Kessler et al., NCS-R). Many medications and therapies work for both. Treatment is chosen with both in mind.
Course and prognosis
With treatment, most people improve substantially. About half of people respond well to their first medication trial. Of those who do not, most respond to a switch or an addition. Roughly half of patients who recover have one or more future episodes in their lifetime, which is why ongoing care, attention to sleep and movement, and relapse awareness matter. Continued treatment after recovery, sometimes for six to twelve months after a first episode and longer after multiple episodes, lowers the risk of relapse.
When urgent care is needed
Suicidal thoughts with intent or a plan. Inability to keep oneself safe. Psychosis. Severe self-neglect. Mania. Threat to self or others. In these situations, call 988, call 911, or go to the nearest emergency department.
Just diagnosed? Read the next-steps guide: I was just diagnosed with depression. What now?
Supporting someone with MDD? See the partner guide: My partner has depression. How can I help?
Related
Just diagnosed with depression: next steps. How to help a partner with depression. Persistent depressive disorder. Bipolar depression. Postpartum depression. Treatment-resistant depression (glossary). Treatment. Suicide and Crisis.
