History of Major Depressive Disorder and Remission Management

Definition & Diagnostic Criteria

A patient who previously required antidepressant therapy for a major depressive episode and now has a PHQ‑9 score of 0 retains a documented history of major depressive disorder, indicating remission rather than absence of disease. 1
Prior treatment for a depressive episode confirms that DSM‑5 criteria were met (depressed mood or anhedonia plus additional symptoms for ≥2 weeks with functional impairment). 1

Acute phase – lasts 6–12 weeks and focuses on initial symptom reduction. 1
Continuation phase – spans 4–9 months after response and aims to prevent relapse of the same episode. 1
Maintenance phase – extends ≥1 year and is intended to prevent recurrence of new depressive episodes. 1
Patients who have achieved full remission but continue therapy are considered to be in the continuation or maintenance phase, where ongoing treatment helps avert relapse despite the absence of symptoms. 1, 2

Relapse is defined as the return of depressive symptoms during the acute or continuation phases, representing a return of the same episode. 1
Recurrence is defined as the emergence of depressive symptoms during the maintenance phase, indicating a new distinct episode. 1

Record the condition as “Major depressive disorder, single episode, in full remission” when the patient has experienced only one episode, or “Major depressive disorder, recurrent, in full remission” if multiple episodes have occurred. 1
Avoid documenting “no history of depression” solely because current symptoms are absent, as this would erase important risk information. 1
Do not remove the depression problem from the active problem list; instead reclassify it as “in remission.” 2
Do not discontinue psychotherapy or pharmacotherapy when PHQ‑9 = 0; continuation‑phase treatment is essential to prevent relapse. 1, 3

Individuals with a prior major depressive episode have a markedly increased risk of future recurrence. 2
After a single episode, continuation‑phase treatment for 4–9 months is recommended. 1, 2
After two or more episodes, clinicians should consider years of maintenance therapy, potentially lifelong, to mitigate recurrence risk. 3
Monthly monitoring for 6–12 months post‑remission is appropriate, with extension up to 2 years for patients with recurrent depression. 3

Conduct structured follow‑up using the PHQ‑9 at regular intervals; scores ≥5 signal emerging depressive symptoms. 1
At each visit, screen for new stressors, medication adherence, and substance use to identify factors that may precipitate relapse or recurrence. 3

If PHQ‑9 scores rise to ≥10, this denotes a new depressive episode that warrants reassessment and possible intensification of treatment, rather than being interpreted as failure of the prior regimen. 3

The cited recommendations are derived from consensus guidelines and expert reviews published in Annals of Internal Medicine (2016, 2022) and supplemented by practical guidance from Praxis Medical Insights (2026). Specific levels of evidence were not enumerated in the source documents.