What is major depressive disorder?

Major depressive disorder (MDD) is a clinical condition involving recurrent or persistent episodes of depressed mood and loss of pleasure, accompanied by a cluster of associated symptoms — sleep disturbance, appetite changes, fatigue, difficulty concentrating, and feelings of worthlessness or guilt — lasting at least two weeks and causing significant functional impairment. It is among the most common and disabling conditions globally.

What does the evidence say about treatment for MDD?

A combination of psychological therapy (particularly CBT) and antidepressant medication is the most evidenced approach for moderate-to-severe MDD. Exercise has robust evidence as an important adjunct. For treatment-resistant depression, options including ECT, ketamine, and TMS have increasing evidence. Lifestyle foundations — sleep, exercise, alcohol reduction, social connection — significantly influence treatment outcomes.

Can complementary therapies play a role in managing major depression?

Yes, as adjuncts. Acupuncture has evidence for reducing depression severity. St John's Wort has evidence comparable to antidepressants for mild-to-moderate depression but has significant drug interactions and should not be taken alongside prescribed antidepressants without medical guidance. Nutritional approaches targeting omega-3 deficiency, gut health, and thyroid function may address specific contributing factors. Mindfulness-based cognitive therapy is a NICE-endorsed relapse prevention approach.

How does depression affect physical health?

Major depression has significant physical health consequences — it is an independent risk factor for cardiovascular disease, diabetes, and immune dysfunction. The inflammation-depression relationship is bidirectional: chronic inflammation contributes to depression, and depression elevates inflammatory markers. This means that physical health interventions — including exercise, anti-inflammatory nutrition, and sleep optimisation — are not separate from mental health treatment but integral to it.

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Major depressive disorder

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Reviewed by Dr. Ava Gardner · Integrative Medicine Researcher26 March 2026Research-supported

Quick answer

Major depressive disorder (MDD) involves severe, persistent low mood, anhedonia, fatigue, and cognitive changes that significantly impair daily functioning. Medical treatment is typically necessary; nutritional psychiatry, therapeutic exercise, and mind-body practices have growing evidence as adjunctive approaches.

Do any of these feel familiar?

Major depressive disorder is experienced as more than sadness — it is a pervasive dimming of life
Many people describe an inability to feel pleasure, meaning, or connection in things that previously mattered
Getting out of bed, eating, washing, and leaving the house can each feel like enormous effort
Persistent feelings of hopelessness, worthlessness, and emptiness are central
Physical symptoms are often significant: disrupted sleep, altered appetite, physical heaviness or agitation, and difficulty concentrating
Many people describe feeling invisible — performing normal life on the outside while experiencing profound inner darkness

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Overview

Symptoms & Affected Systems

Contributing Factors

Supporting Lifestyle Strategies

Evidence Context

When to Seek Professional Help

Related Conditions

Depression

Dysthymic Disorder

Bipolar

Anxiety

Treatment Resistant Depression

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