Five or more symptoms are present during the same 2-week period and represent a change from previous functioning.
At least one of the symptoms is either depressed mood or markedly diminished interest or pleasure.
The symptom set may include depressed mood most of the day, nearly every day.
The symptom set may include markedly diminished interest or pleasure in nearly all activities.
The symptom set may include significant weight loss, weight gain, or appetite change when not dieting.
The symptom set may include insomnia or hypersomnia nearly every day.
The symptom set may include psychomotor agitation or retardation observable by others.
The symptom set may include fatigue or loss of energy nearly every day.
The symptom set may include feelings of worthlessness or excessive or inappropriate guilt.
The symptom set may include diminished ability to think, concentrate, or make decisions.
The symptom set may include recurrent thoughts of death, suicidal ideation, a suicide plan, or a suicide attempt.

The symptoms cause clinically significant distress or impairment in social, occupational, or other important areas of functioning.

The presentation is not better explained by a schizophrenia-spectrum or other psychotic disorder.

There has never been a manic or hypomanic episode unless clearly substance- or medically induced.

Major depressive disorder is usually the picture people imagine when they think of a true depressive episode: a sustained drop in mood or interest, plus changes in sleep, energy, appetite, thinking, and day-to-day functioning that feel like a clear shift from the person's baseline.
Clinical frame: Think in episodes. The key question is whether this looks like at least 2 weeks of symptoms that clearly differ from the person's usual self.
Rule-outs: Before settling on MDD, slow down and check for bipolarity, substance effects, psychosis, grief context, and medical contributors.
Specifier thinking: Once the episode is established, the next useful step is asking how it presents: anxious distress, melancholic features, psychosis, seasonality, catatonia, or peripartum onset can all change management.
Clinical focus: Fast symptom burden tracking in outpatient settings.

Fast symptom burden tracking in outpatient settings.

Clinician-rated depression severity, often used in specialty care and research.

Useful when you want a brief depressive symptom measure with repeated follow-up.

Sensitive to change during treatment response assessment.

Common FDA-indicated antidepressants for MDD; agent choice still depends on age, comorbidity, and adverse-effect profile.

These are FDA-indicated as add-on treatments rather than stand-alone first-line monotherapy for routine MDD care.

ECT is established for severe or psychotic depression and is often considered when rapid response is needed.
Repetitive TMS is used in treatment-resistant depression.
Ketamine or esketamine-based strategies are used in treatment-resistant depression settings.

Simple Psych

Major Depressive Disorder