Persistent depressive disorder: symptoms, causes and treatment

Key points

• Persistent depressive disorder is low mood on most days for at least two years, plus at least two other depressive symptoms [7][10].
• Dysthymia is the older name. DSM-5 merged dysthymia and chronic major depression into one diagnosis; ICD-11 keeps dysthymic disorder separate, as 6A72 [7][10].
• The mood is steady rather than dramatic, so many people keep working and go undiagnosed for years [7].
• Double depression is a major depressive episode on top of the chronic low mood, and often what brings someone to a GP [7][8].
• “High functioning depression” is a search term, not a diagnosis, and appears in neither ICD-11 nor DSM-5-TR [10].
• NICE lists separate first treatments for chronic depression, and the research base is thinner than for episodic depression [1][2][9].

What persistent depressive disorder is

Persistent depressive disorder is a form of depression in which low mood lasts for years rather than arriving in episodes. The depressed mood is present most of the day, more days than not, for at least two years, alongside at least two other symptoms such as poor appetite or overeating, sleep problems, low energy, low self-esteem, poor concentration or hopelessness [7].

If you need help now. Samaritans: call 116 123, free, 24/7. Shout: text SHOUT to 85258. NHS 111, then choose the mental health option. Call 999 if anyone is in immediate danger.

No reliable UK prevalence figure exists. A Cochrane review reports 3% to 6% of people in Western countries are affected at some point in life [8].

The two diagnostic systems name it differently. DSM-5, the American manual, combined dysthymia and chronic major depression into one diagnosis in 2013 [7]. ICD-11, the World Health Organization’s current classification, keeps dysthymic disorder as a separate category [10]. UK records are more likely to say dysthymia; persistent depressive disorder is the research term.

“High functioning depression” is not a diagnostic term and is not listed in ICD-11 or DSM-5-TR [10]. It usually means holding down a job and a social life while feeling persistently flat underneath, a common pattern here [7]. Functioning is not a measure of severity.

Symptoms

Symptoms are usually milder than in a severe depressive episode but last far longer, so they are often read as personality rather than illness [7].

Mood and thinking:

• low mood most of the day, more days than not [7][10]
• low self-esteem, self-criticism and indecision [7]
• hopelessness, or a settled belief that this is how life is [7]

Body and energy:

• low energy or tiredness that rest does not fix [7]
• sleeping or eating too little or too much [7][10]

Day to day:

• getting work done while taking little pleasure in any of it [7][10]
• pulling back from friends and family, and irritability in close relationships [7]

It is commonly mistaken for a personality trait, for burnout, or for an underactive thyroid, which can itself cause depressive symptoms [4]. A history of mania or hypomania rules out this diagnosis [7].

Types

ICD-11 does not divide dysthymic disorder into subtypes, so recognised presentations are used instead [10]. A Cochrane review groups persistent depression into four [8]:

• Dysthymia. Long-running symptoms that never reach the threshold for a full depressive episode [8][10].
• Chronic major depression. A depressive episode that has continued for two years or more [8].
• Recurrent major depression with incomplete remission. Episodes return and mood never fully recovers in between [8].
• Double depression. A major depressive episode on top of existing chronic low mood [7][8].

Causes and risk factors

There is no single cause. Depression is multifactorial, with biological, social and psychological factors involved, so single cause explanations such as a chemical imbalance do not fit the evidence [7].

Factors linked to chronic rather than episodic depression [7]:

• childhood adversity, maltreatment, or loss of a parent
• higher rates of chronic depression among close relatives
• an earlier age at first onset than in episodic depression
• more traumatic events across a lifetime
• high anxiety and neuroticism

The NHS also links depression to stressful life events, loneliness, heavy alcohol or drug use, long-term illness and family history [4]. Keeping up with work is not a protective factor: the outlook is described as similar to or worse than that of major depressive disorder [7].

How it is diagnosed

In the UK a GP usually assesses this first, and the NHS advises against delaying that appointment [4]. Psychiatrists, registered with the GMC, and practitioner psychologists, registered with the HCPC, diagnose in specialist services.

The assessment is a conversation about symptoms, how long they have lasted and what they prevent. Because the defining feature is duration, a GP looks at years rather than weeks, and may ask when the person last felt like themselves. Physical causes may be checked too, since an underactive thyroid can cause depressive symptoms [4].

Questionnaires support the assessment but do not make the diagnosis. NICE uses the PHQ-9, with 16 as the cut-point between less severe and more severe depression [3], but it asks only about the past two weeks, so it cannot show a two-year pattern [3][7]. A diagnosis names that pattern and opens access to treatment. It does not mean the low mood is permanent, and it is not a description of personality.

Treatment

NICE sets out a separate list for chronic depression rather than treating it as a longer version of a new episode [1]. As initial treatment it says to consider CBT, an SSRI, an SNRI, a tricyclic antidepressant, or CBT combined with an SSRI or tricyclic [2].

If there is no response, NICE lists further options that need specialist advice, including tricyclic antidepressants, moclobemide, irreversible MAOIs and low dose amisulpride [2]. It also suggests vocational and social rehabilitation, befriending, or both, to restore day to day functioning [2]. Decisions about medication belong with a prescriber, and where an antidepressant helps NICE advises continuing it for at least six months after symptoms settle [3].

The evidence base is thinner than for episodic depression, and there is little research on how well medication or psychotherapy work in this condition [7]. A meta-analysis of 16 randomised trials found psychotherapy had a small but significant effect in chronic depression and dysthymia, was less effective than medication in direct comparisons, and worked better combined with it [9]. A Cochrane review of longer-term treatment found only 10 studies, too few for firm conclusions [8].

Treatment usually takes longer than for a single episode, and progress is measured over months.

Living with persistent depressive disorder

Change tends to be gradual, so it helps to track mood over months rather than days. A simple record of sleep, activity and mood gives you and your clinician something to compare against.

Steps NICE and the NHS suggest:

• ask about vocational or social rehabilitation, or befriending, which NICE lists for chronic depression [2]
• keep regular contact with other people, since loneliness raises risk [4]
• look at alcohol and drug use honestly, since using them to cope tends to deepen depression [4]
• refer yourself to NHS Talking Therapies if you are 18 or over [5]

At work or university you do not have to give a diagnosis to ask for adjustments: saying what you find difficult and what would help is usually enough. Information and peer support are available through Mind [6].

When to speak to a professional

Speak to a GP if:

• low mood has been present most days for two years or more [7]
• you cannot remember the last time you felt well [7]
• the low mood has recently deepened, or new symptoms have appeared [7][8]
• treatment already tried has not helped [2]
• you are using alcohol or drugs to cope [4]

If you are 18 or over in England and registered with a GP, you can refer yourself to NHS Talking Therapies [5].

Get help straight away if you are struggling to keep yourself safe. Samaritans: call 116 123, free, 24/7. Shout: text SHOUT to 85258. NHS 111, then the mental health option. Call 999 if anyone is in immediate danger.

Common questions

What does high functioning depression mean?

It is not a clinical diagnosis and does not appear in ICD-11 or DSM-5-TR [10]. People use it to mean carrying on with work and daily life while feeling persistently low, a common pattern in this condition [7]. Coping well does not rule it out.

What is double depression?

Double depression is a major depressive episode developing on top of long-running chronic low mood [7][8]. The change is usually noticeable to the person and to those around them, and often prompts a first GP appointment.

How long does treatment take?

Longer than for a single episode. NICE advises continuing an antidepressant that helps for at least six months after symptoms settle [3], and research on chronic depression reports outcomes in months, not weeks [8][9].

Clinical review pending

References

1. National Institute for Health and Care Excellence. Depression in adults: treatment and management (NG222), recommendations. NICE, 2022. https://www.nice.org.uk/guidance/ng222/chapter/recommendations
2. National Institute for Health and Care Excellence. Treatment options for chronic depression, depression with personality disorder or psychotic depression. NG222 visual summary, PDF. NICE, 2022. https://www.nice.org.uk/guidance/ng222/resources/treatment-options-for-chronic-depression-depression-with-personality-disorder-or-psychotic-depression-pdf-11131007010
3. National Institute for Health and Care Excellence. Depression in adults: treatment and management. NICE guideline NG222, full guideline PDF. NICE, 2022. https://www.nice.org.uk/guidance/ng222/resources/depression-in-adults-treatment-and-management-pdf-66143832307909
4. NHS. Depression in adults: overview and causes. NHS. https://www.nhs.uk/mental-health/conditions/depression-in-adults/overview/ , https://www.nhs.uk/mental-health/conditions/depression-in-adults/causes/
5. NHS. NHS talking therapies for anxiety and depression. NHS. https://www.nhs.uk/mental-health/talking-therapies-medicine-treatments/talking-therapies-and-counselling/nhs-talking-therapies/
6. Mind. About depression. mind.org.uk. https://www.mind.org.uk/information-support/types-of-mental-health-problems/depression/about-depression/
7. StatPearls Publishing. Persistent Depressive Disorder. StatPearls, NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK541052/
8. Machmutow K and colleagues. Comparative effectiveness of continuation and maintenance treatments for persistent depressive disorder in adults. Cochrane Database of Systematic Reviews, 2019. https://www.cochrane.org/evidence/CD012855_long-term-treatment-people-persistent-depression
9. Cuijpers P, van Straten A, Schuurmans J, van Oppen P, Hollon SD, Andersson G. Psychotherapy for chronic major depression and dysthymia: a meta-analysis. Clinical Psychology Review, 2010, 30(1), 51 to 62. Abstract and quality assessment via Database of Abstracts of Reviews of Effects, NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK77927/
10. ICD-11 MMS entries 6A72 Dysthymic disorder and the Depressive disorders block, as reproduced by Find-A-Code. https://www.findacode.com/icd-11/code-810797047.html , https://www.findacode.com/icd-11/block-1563440232.html