The main division between depression subtypes is duration rather than severity. Major depressive disorder requires at least two weeks of depressed mood or loss of interest plus a set number of further symptoms. Persistent depressive disorder requires depressed mood on most days for at least two years in adults, usually with fewer symptoms present at any one moment. [apa-2022-dsm5tr]
That framing corrects the assumption most people arrive with, which is that these are the severe and mild versions of the same thing. They are not ranked that way, and the review evidence describes persistent depressive disorder as frequently more disabling than episodic major depression, for a reason that is obvious once stated: it does not lift. [schramm-2020-pdd]
What changed when dysthymia became persistent depressive disorder
Dysthymia was a DSM-IV diagnosis for chronic low-grade depression. DSM-5 replaced it with persistent depressive disorder and, importantly, made the new category wider: it subsumes dysthymia with or without superimposed major depressive episodes, chronic major depression, and recurrent major depression without full recovery between episodes. [schramm-2020-pdd]
So persistent depressive disorder is not simply dysthymia renamed. It gathers several chronic presentations that were previously scattered, on the reasoning that chronicity itself is the clinically important feature. That is why older sources and newer ones can seem to disagree, and why “dysthymia” still appears widely in everyday use.
Major depressive disorder: the two-week threshold
A major depressive episode requires depressed mood or loss of interest and pleasure for at least two weeks, with at least four additional symptoms from a list covering appetite or weight change, sleep disturbance, fatigue, poor concentration, feelings of worthlessness or guilt, psychomotor changes and recurrent thoughts of death. [apa-2022-dsm5tr] The symptoms must cause significant distress or impairment.
Two features of that definition are routinely missed. Loss of interest can substitute for low mood, so someone who feels flat and unmotivated rather than sad can still meet the criteria. And the episode is bounded, at least in principle, which is what makes it episodic: there is a before and, usually, an after.
Persistent depressive disorder: the two-year threshold
Here the requirement is depressed mood for most of the day, on more days than not, for at least two years in adults and one year in children and adolescents, with at least two additional symptoms and no symptom-free period longer than two months. [apa-2022-dsm5tr]
The clinical picture that produces is different in kind. People often do not describe themselves as depressed at all, because there is no contrast to point at; the low mood has been the baseline long enough to read as personality. That is the practical reason it goes undiagnosed for years, and it is the reason the two-month clause is in the criteria: it is testing for the absence of genuine recovery, not for the presence of severe symptoms.
A schematic contrast of the episodic and persistent courses described in this article, not measured data. Individual courses vary widely.
The left-hand pattern is worse on its worst day. The right-hand pattern removes more from a life, and it is the one people are least likely to bring to a GP, because nothing about it feels like an event.
Double depression, and why it matters at discharge
When a major depressive episode lands on top of pre-existing persistent depression, the older literature called it double depression, and DSM-5 handles it by allowing both diagnoses to be recorded. [schramm-2020-pdd] It is common rather than unusual.
The reason to know the term is what happens when the acute episode resolves. The baseline someone returns to is not wellness, it is their persistent low mood, and treatment that stops at the point the acute episode lifts leaves the chronic condition entirely untreated. From the outside this looks like successful treatment. From the inside it looks like getting back to feeling the way you always felt, which is exactly the thing that needed addressing.
The specifiers, which are not separate conditions
Alongside the duration split, DSM-5-TR describes the character of an episode using specifiers rather than separate diagnoses: with anxious distress, with melancholic features, with atypical features, with psychotic features, with peripartum onset, and with seasonal pattern. [apa-2022-dsm5tr]
These are worth recording because several carry treatment implications, and worth understanding correctly because they describe an episode rather than a person. Someone can have one episode with melancholic features and a later one without. Two of them have dedicated coverage here: postnatal depression for peripartum onset, and treatment-resistant depression for the separate question of what happens when treatments do not work.
Which pattern does yours look more like?
Think about the last two years rather than the last two weeks, which is the timescale that separates these. This is a reflection prompt, not a diagnostic tool.
0 of 8 ticked
Several of these point at a persistent rather than an episodic pattern, and that is the one most often missed because it does not feel like an event. It is specifically worth telling a GP how long it has been going on rather than only how bad it is now.
Some of what you ticked fits an episodic course and some a chronic one, which is common and is exactly the combination worth describing to a clinician rather than resolving yourself. The screener below gives you a score to bring.
Little here matches either course. If mood is still a concern, the depression screener below covers the last two weeks specifically and takes about two minutes.
The free depression screener uses PHQ-9, the questionnaire most GPs use. It asks about the last two weeks, so it measures current severity rather than the duration that separates these diagnoses, and that limitation is worth knowing when you read your score. Two minutes, nothing sent anywhere. Our guide to how to deal with depression covers what helps day to day.
What the distinction changes about treatment
Less than people expect about the first choice, and more than people expect about duration. Chronic presentations tend to respond less well to brief treatment and generally need a longer course, and specific psychotherapies have been developed for chronic depression rather than adapted from acute protocols. [schramm-2020-pdd]
On medication, the network meta-analysis covering 522 trials and over 116,000 patients found all 21 antidepressants studied more effective than placebo for acute major depression, with SSRIs such as sertraline and escitalopram best balanced for efficacy and tolerability. [cipriani-2018-antidepressants] That evidence base is about acute episodes, which is a real limitation when the presentation is chronic, and it is one reason expectations need setting differently.
The practical consequence is about interpretation. An eight-week course producing partial improvement in a two-year depression can read as a failed treatment when it is an incomplete one, and that misreading is a common route to giving up on something that was working slowly. Our guide to new antidepressants covers what has changed recently and what has not.
When to seek help
The signal is persistence. Two weeks or more of low mood or loss of interest that is affecting work, relationships or basic self-care is worth raising with a GP. If the honest answer to “how long has this been going on” is measured in years rather than weeks, say that explicitly, because it is the single most useful thing you can tell a clinician and it is the thing most likely to go unsaid.
Go urgently if you are having thoughts of harming yourself or that life is not worth living. Contact your GP urgently, or use an emergency service or crisis line where you are.
How MyFreud can help
The distinction this article turns on is duration, and duration is the one thing memory reports badly, particularly when the baseline has been low for years. MyFreud gives you daily mood tracking that builds the record the diagnosis actually depends on, so you can show a GP whether there has been a genuinely well stretch in the last two years rather than trying to recall one. That is a more useful answer than a number describing this week.
Download MyFreud and start today: App Store or Google Play.