Persistent depressive disorder: long-term low mood and its treatment

Persistent depressive disorder, also known as dysthymia, is the label used in psychiatric classification for depression that continues over a long period. In UK guidance the equivalent idea is chronic depressive symptoms. NICE Clinical Knowledge Summaries defines these as symptoms that continually meet the criteria for a major depressive episode for at least two years, or persistent subthreshold symptoms for at least two years, or persistent low mood with or without concurrent episodes of major depression for at least two years.

The practical point is the duration. NHS inform describes depression as something that can be a single event, recurring episodes or continuous, known as chronic depression. People with long-term low mood may not describe themselves as depressed at all, because the symptoms have become the background of daily life.

The NHS describes depression as a persistent sadness for weeks or months that is bad enough to interfere with work, social life and family life. Psychological symptoms include continuous low mood, hopelessness, low self-esteem, tearfulness, guilt, irritability, lack of motivation, difficulty making decisions and not getting enjoyment from life. Physical features include slower movement or speech, changes in appetite or weight, constipation, unexplained aches and pains, lack of energy, low sex drive and disturbed sleep.

There are social effects too: avoiding friends, doing fewer activities, neglecting hobbies and finding home or work life harder. The NHS also notes that depression often comes on gradually, so it is hard to notice, and that a friend or family member sometimes has to point it out. Some people also have suicidal thoughts; the NHS lists this among the symptoms, and support is available through a GP, NHS 111 or the Samaritans on 116 123.

A GP will ask about symptoms, how long they have lasted, how they affect daily life, past episodes, physical health, medicines and alcohol or drug use. NICE CKS says assessment includes onset, duration, pattern and severity, coexisting conditions, family history, suicidal ideas and the use of a validated questionnaire to assess severity and response to treatment.

The NICE guideline distinguishes less severe from more severe depression using the PHQ-9 questionnaire, with a score below 16 as less severe and 16 or more as more severe. NICE CKS says a physical examination and further investigations are considered where indicated, and the diagnosis is reconsidered if treatment is not working. The NHS notes that depression can also be a feature of other conditions such as bipolar disorder, so the whole picture is reviewed.

The NHS says treatment depends on severity and may involve lifestyle changes, talking therapies and medicine. For moderate to severe depression, antidepressants plus talking therapy are often recommended, and the NHS says a combination of an antidepressant and CBT usually works better than either on its own. Cognitive behavioural therapy usually runs for 8 to 16 sessions, with once-weekly or fortnightly sessions. Other talking therapies listed include interpersonal therapy, behavioural activation, counselling and psychodynamic psychotherapy.

Antidepressants usually need to be reviewed every week or two for at least 4 weeks after starting, and the NHS says symptoms should start improving within 4 weeks. If they help, they are generally continued for at least 4 to 6 months after symptoms ease, and longer for those with previous episodes. A person may need to try two or more before finding one that works. Antidepressants are not addictive, but stopping suddenly can cause withdrawal symptoms, so any change should be planned with the prescriber.

NICE CKS advises that if there is no improvement, options include switching therapy, adding or increasing an antidepressant or combining psychological and drug treatment, and that specialist mental health services should be involved for chronic depressive symptoms affecting personal and social functioning that have not responded in primary care.

Exercise is described by the NHS as one of the main treatments for mild depression, and the NHS lists getting more exercise, cutting down alcohol, giving up smoking and eating healthily as helpful lifestyle changes. Guided self-help based on CBT principles usually runs for 6 to 8 sessions, and reading a self-help book or joining a support group can also help.

People can refer themselves directly to an NHS talking therapies service without seeing a GP, though the NHS warns waiting times can be several weeks or months and a GP can advise what to do if things worsen in the meantime. Supporters can help by encouraging professional help, letting the person know they are not alone and offering to help find solutions.

Long-standing depression can feel entrenched, but NICE says that with the right treatment and support people with depression can make a good recovery. NICE also stresses shared decision-making: your treatment should be chosen together with your healthcare professional, taking account of your preferences, your previous experience of treatments and the benefits and risks, including side effects and possible withdrawal effects.

Because depression that has lasted years may take longer to respond, it is reasonable to expect a gradual change rather than a sudden one, and to agree review points. Relapse prevention is part of ongoing care, and those with previous episodes may stay on medication long term with at least twice-yearly reviews, according to the NHS.