Persistent depressive disorder, which nearly everybody still calls dysthymia, is low mood that has been there for at least two years. Major depressive disorder is an episode, usually more intense, that qualifies after two weeks. The difference is duration and shape over time rather than how much it hurts, and reading it as a severity ranking is why the long version goes unnamed for a decade at a stretch.
What separates dysthymia from major depression
Duration is the whole answer. Major depressive disorder requires at least two weeks of depressed mood or loss of interest, alongside enough further symptoms to reach five in total, and it is described as an episode because that is how it behaves. [apa-depression] Persistent depressive disorder requires depressed mood most of the day, more days than not, for at least two years in adults, and at least one year in children and adolescents. [nimh-pdd]
Intensity usually differs as well, and this is where the reasoning goes wrong. The persistent form is generally lower at any single moment, so people file it as the mild one. Mild is not what the criteria say. They say long, and severity is recorded separately from duration in the manual clinicians work from, which is precisely so that a chronic presentation can be marked severe when it is. [apa-dsm]
One more thing about the name, since you will meet both words in the same conversation and sometimes in the same clinic letter. Dysthymia was the label in the previous edition of the manual and it was folded into persistent depressive disorder when the classification was revised. [apa-dsm] They point at the same territory. Persistent depressive disorder is the wider of the two, because it also takes in chronic major depression that has never fully remitted.
| Persistent depressive disorder | Major depressive disorder | |
|---|---|---|
| Minimum duration | Two years in adults, one year in children and adolescents | Two weeks |
| Intensity at its worst | Usually lower, and steady | Usually higher, and it moves |
| Course | Continuous, with few or no clear breaks | Episodic, with recovery in between |
| How it is usually noticed | By somebody else, or after many years | By the person, because something changed |
| What people say about it | ”This is just how I am" | "I have not been myself since March” |
Our guide to the depression subtypes and what each one is called covers the classification itself, including the specifiers that can sit on top of either diagnosis. This article is about what the split does to a person.
Why persistent depression gets mistaken for personality
Because there is no before. Somebody whose low mood settled in at fifteen and who is now thirty-four has no earlier version of themselves to hold it against, so the flatness registers as temperament rather than as a condition with a name and a treatment.
The result is a set of self-descriptions that sound nothing like symptoms. I am just a pessimist. I have never been a high-energy person. I am fine, this is only my baseline. Nobody says any of that to a doctor, because none of it feels like information a doctor would want.
Two things follow from that, and both make the delay worse. The people closest to the person describe them the same way, so there is no one in the room to contradict it. And the criteria are quietly being met the whole time: poor sleep or too much of it, low energy, poor appetite or overeating, poor concentration, low self-esteem, hopelessness. Those are not personality traits. They are the list.
Onset age is a large part of why this happens. The persistent form frequently begins early, in adolescence or the early twenties, at the exact point somebody is working out what sort of person they are. A condition that arrives at forty interrupts a self that is already known. A condition that arrives at fifteen becomes part of the answer to the question of who you turned out to be, and prising the two apart afterwards usually takes an outside observer or a specific question from a clinician.
Our article on why the phrase high-functioning depression delays help covers the version of this that happens when somebody is still turning in good work while all of it is true.
What double depression means
Double depression is a major depressive episode landing on top of an existing persistent depressive disorder. It is a description rather than a separate diagnosis, and it is common rather than exotic, because a chronic low baseline is a poor position from which to absorb a bereavement or a redundancy.
The part people misread is what recovery from the episode looks like. It returns the person to their chronic baseline, not to feeling well, so the improvement is real and the destination is still low. Treatment then reads as having half worked, and the usual conclusion is that the medication or the therapy failed.
It did not fail. It treated one of the two layers. The chronic layer needs naming as a target of its own, which requires somebody to have asked the two-year question in the first place.
Why the milder diagnosis often costs more
Because it does not lift, and the damage accumulates rather than resolving. Of US adults who had persistent depressive disorder in the past year, an estimated 49.7% had serious impairment on a standard disability scale, 32.1% moderate and 18.2% mild. [nimh-pdd] Roughly half at serious impairment is not the shape of a mild condition.
Think about what the two courses remove from a life. An episode takes months and gives them back. A persistent low mood takes a fraction of every month and never gives any of it back, and over twenty years that fraction is the larger total. Careers, friendships and the decision to apply for anything at all are all eroded slowly rather than interrupted sharply.
A schematic of the two courses described here, to show shape over time rather than measured data.
The condition is not rare, either. An estimated 1.5% of US adults had persistent depressive disorder in a given year, and about 2.5% will have it at some point in life. [nimh-pdd] Against a global population that is a very large number of people who have never had a word for what they have.
What treatment looks like for each
Both respond to the same two families of treatment, which is the most useful thing in this article. For adults, the recommended starting point is psychotherapy or a second-generation antidepressant, and combining cognitive behavioural or interpersonal therapy with medication is also recommended. [apa-guideline] Nothing about the chronic form puts it outside that.
What changes is the yardstick you judge progress by. Eight weeks against a two-week episode is a complete trial of a treatment. Eight weeks against a baseline that has been in place since school is a short look, and the risk is that somebody with two decades behind them concludes after two months that treatment does not work for them and stops.
There is an asymmetry in how the two get spotted in an appointment, and it works against the chronic one. An episode announces itself, because the person can describe a change and roughly when it started. A twenty-year baseline announces nothing at all, so the question has to come from the other side of the desk, and it is a short question: how long has this been going on, and when were you last well? Where nobody asks it, the persistent form stays invisible in a room full of people trained to look for it.
So say the number yourself. Whoever is treating you needs to know that the low mood has been there for eleven years rather than since March, because it changes what counts as improvement, how long to persist before switching, and whether the goal is getting back to how you were or finding out what your baseline could be. Our depression guide covers the treatment options in more detail.
How to work out which one describes you
Ask when you last felt like yourself, and take the answer seriously. If you can name a rough date, a season, a job, a year, you are most likely describing an episode with a beginning. If you cannot find one, or the honest answer is that you never really have, that is the pattern the persistent diagnosis was written for.
Then check the second question, which is what most people skip. Has something got worse recently on top of the usual? A recent change over a long-standing baseline is what double depression looks like from the inside, and it is the version most likely to bring somebody to an appointment.
Our free depression screener uses a standard nine-item questionnaire and takes about two minutes. One caveat is worth carrying into it: the screener asks how you have been over the last two weeks, so it reads an episode clearly and reads a twenty-year baseline as whatever today happens to be. It produces no diagnosis. Bring your answer to the two-year question with you.
When to seek help
Speak to a doctor if low mood has been present on most days for two years or longer, even if you have never thought of it as depression, and even if you are still holding down work and relationships. Length is a reason to go rather than evidence that nothing can be done.
Go sooner if something has changed on top of the usual baseline in recent weeks, if sleep or concentration has dropped further, or if you have stopped doing things you were still managing a year ago. Say how long the low mood has been there, in years if that is the true answer, because that single number changes both the diagnosis and the plan.
Contact your local emergency services or a crisis helpline if you feel unsafe or have thoughts of harming yourself.
How MyFreud can help
MyFreud is a mobile app that helps you find solutions to problems that have affected your mind and productivity. Live coaching sessions give you somewhere to work out whether what you are describing had a start date or has always been there, which is the question that separates these two diagnoses, each one ends with an actionable plan rather than a label, daily mood tracking builds the record a two-year pattern needs and that nobody can reconstruct from memory, and the notepad is where the timeline lives until you can hand it to somebody.
Download MyFreud and start today: App Store or Google Play.