| Conditions covered | 6 recognised depressive disorder types (DSM-5, American Psychiatric Association) |
| Minimum duration for MDD diagnosis | 2 weeks of symptoms (DSM-5 diagnostic criteria) |
| Minimum duration for persistent depressive disorder | 2 years (adults) (DSM-5 diagnostic criteria) |
| SAD seasonal pattern | Typically autumn/winter onset, spring remission (National Institute of Mental Health (NIMH)) |
| Postpartum depression onset | Within weeks of childbirth; distinct from 'baby blues' (American College of Obstetricians and Gynecologists) |
| Crisis support (US) | Call or text 988 (Suicide & Crisis Lifeline) (SAMHSA, active nationwide) |
Depression Is Not One Thing
When most people hear the word "depression," they picture a single condition — persistent sadness that doesn't go away. But depression is actually a family of related mood disorders, each with its own distinct pattern, duration, and triggers. Understanding those differences matters, because the right support often depends on identifying which type is at play.
This reference guide walks through the most recognised forms of depression using plain language, so you can better understand what clinicians mean and feel more informed in conversations with a healthcare provider. As always, only a qualified mental health professional can assess, diagnose, or treat a mood disorder — this article is for education, not diagnosis.
For a deeper look at what the experience actually feels like day-to-day, see what depression actually feels like beyond sadness.
| Conditions covered | 6 recognised depressive disorder types (DSM-5, American Psychiatric Association) |
| Minimum duration for MDD diagnosis | 2 weeks of symptoms (DSM-5 diagnostic criteria) |
| Minimum duration for persistent depressive disorder | 2 years (adults) (DSM-5 diagnostic criteria) |
| SAD seasonal pattern | Typically autumn/winter onset, spring remission (National Institute of Mental Health (NIMH)) |
| Postpartum depression onset | Within weeks of childbirth; distinct from 'baby blues' (American College of Obstetricians and Gynecologists) |
| Crisis support (US) | Call or text 988 (Suicide & Crisis Lifeline) (SAMHSA, active nationwide) |
The Major Types of Depression Explained
The following are the primary depressive disorders recognised in clinical practice, based on the DSM-5 published by the American Psychiatric Association.
Major Depressive Disorder (MDD)
A clinical diagnosis involving a persistently depressed mood or loss of interest for at least two weeks, significant enough to impair daily functioning. It is one of the most common mental health conditions worldwide.
Persistent Depressive Disorder
Also called dysthymia, this is a chronic form of depression lasting at least two years in adults. Symptoms are generally less severe than MDD but more long-lasting.
Seasonal Affective Disorder (SAD)
A subtype of depression that follows a seasonal pattern, most commonly appearing in autumn and winter when daylight hours are shorter. It is considered a clinical condition, not simply low winter spirits.
Postpartum Depression
A depressive episode beginning after childbirth, lasting beyond the first two weeks and significantly affecting mood, energy, and functioning. It is a medical condition that responds well to treatment.
PMDD
Premenstrual Dysphoric Disorder is a severe mood condition linked to the menstrual cycle, causing significant depression and irritability in the days before menstruation that resolve after the period begins.
DSM-5
The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition — the standard reference used by clinicians in the US to define, categorise, and diagnose mental health conditions.
Major Depressive Disorder (MDD)
Often simply called "clinical depression," MDD involves a depressed mood or loss of interest in activities for at least two weeks, alongside symptoms such as sleep changes, fatigue, difficulty concentrating, and feelings of worthlessness. It can occur as a single episode or recur throughout a person's life. Not sure whether what you're experiencing is MDD or just a rough patch? learn what sets them apart.
Persistent Depressive Disorder (Dysthymia)
Persistent depressive disorder, formerly called dysthymia, involves a chronically low mood lasting at least two years in adults. The symptoms tend to be less severe than MDD but more enduring — sometimes so long-standing that people assume it's just their personality, rather than a treatable condition.
Seasonal Affective Disorder (SAD)
SAD is a subtype of MDD tied to seasonal light changes. Most commonly, symptoms emerge in late autumn and winter, then resolve in spring. Reduced sunlight is thought to disrupt circadian rhythms and affect serotonin and melatonin levels. It's far more than the "winter blues" — for many people, it significantly impairs daily functioning.
Postpartum Depression
Distinct from the short-lived "baby blues," postpartum depression involves persistent low mood, exhaustion, and difficulty bonding that begins within weeks of childbirth and can last months. It affects a meaningful proportion of new parents and is a medical condition — not a reflection of parenting ability or love for a child. Anyone experiencing this should speak with a healthcare provider promptly.
Premenstrual Dysphoric Disorder (PMDD)
PMDD involves severe mood symptoms — including depression, irritability, and anxiety — tied to the luteal phase of the menstrual cycle. Symptoms typically resolve shortly after menstruation begins. It is more intense than typical premenstrual syndrome and can significantly affect relationships and work.
Disruptive Mood Dysregulation Disorder (DMDD)
Primarily diagnosed in children and adolescents, DMDD is characterised by severe, recurrent temper outbursts and a persistently irritable or angry mood between episodes. It was introduced in the DSM-5 to more accurately capture what was previously often mislabelled.
A Note on Diagnosis and Overlap
Some people experience features of more than one depressive disorder at the same time, and presentations can shift over time. A formal diagnosis requires a thorough clinical assessment — self-identifying with a category based on an article is not a substitute. If you're uncertain, speaking with a licensed mental health professional is always the right move. For more on how diagnoses work in general, see our plain-language guide to understanding diagnoses.
For a comprehensive look at causes, symptoms, and treatment pathways across depressive disorders, visit our full guide to depression.
When to Reach Out for Support
Regardless of the type, depression is treatable — and reaching out is a sign of strength, not weakness. If you or someone you know is experiencing low mood that interferes with daily life, relationships, or physical wellbeing, speaking with a primary care physician or licensed mental health professional is the recommended first step. It's also worth knowing that depression has real physical symptoms that are easy to overlook or misattribute.
In a mental health crisis or emergency, contact the 988 Suicide and Crisis Lifeline (call or text 988 in the US) or go to your nearest emergency room.
This article is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with any questions about a mental health condition.