Dysthymic Disorder (Persistent Depressive Disorder)

What persistent depressive disorder is

PDD combines two older diagnoses: dysthymic disorder and chronic major depressive disorder. Its defining feature is duration rather than severity. The low mood is present more days than not for at least 2 years, and symptom-free periods never last longer than 2 months.

Because it often starts in childhood, adolescence or early adulthood and lasts so long, many people do not recognize it as an illness. They may describe themselves as pessimistic, a worrier or "just not a happy person". People with PDD often keep functioning at work or school, which is why it is sometimes called "high-functioning depression".

Symptoms

Depressed mood (or irritability in children and teens) most of the day, more days than not, plus two or more of:

• poor appetite or overeating
• insomnia or sleeping too much
• low energy or tiredness
• low self-esteem
• poor concentration or difficulty making decisions
• feelings of hopelessness

Other common features:

• loss of interest or pleasure in activities
• social withdrawal
• feeling guilty or self-critical
• irritability and anger
• reduced productivity
• lower sex drive

Double depression

About three quarters of people with PDD also have episodes of major depression at some point. This is called double depression: a baseline of chronic low mood with periods of more severe depression on top.

Dysthymia vs major depression

PDD is not a "mild" problem. Because it lasts so long, its total effect on quality of life can be as great as major depression.

Causes and risk factors

• Genetics: depression in close relatives
• Brain chemistry and stress hormone systems
• Early adversity: childhood abuse, neglect or loss
• Ongoing stress: chronic illness, caregiving, poverty, relationship problems
• Personality traits: high anxiety, perfectionism, self-criticism
• Other conditions: anxiety disorders, substance use disorder, PTSD, chronic pain, eating disorders

Diagnosis

A primary care doctor, psychiatrist, psychologist or counselor diagnoses PDD by asking about symptoms, how long they have lasted and how they affect life. Questionnaires such as the PHQ-9 help measure severity.

Medical causes of low mood and fatigue, such as hypothyroidism, anemia, vitamin deficiencies and medicine side effects, may be checked with blood tests. Clinicians also screen for bipolar disorder, because antidepressants alone can trigger mania in people with bipolar disorder.

Treatment

Psychotherapy

• Cognitive behavioral therapy (CBT): challenges negative thinking patterns and builds rewarding activity.
• Cognitive Behavioral Analysis System of Psychotherapy (CBASP): developed specifically for chronic depression, focusing on how behavior affects relationships.
• Interpersonal therapy: improves relationships and life transitions.
• Behavioral activation: gradually adding meaningful activities.

Medicines

• SSRIs (sertraline, escitalopram, fluoxetine) and SNRIs (venlafaxine, duloxetine) are commonly used.
• Other options include bupropion, mirtazapine and tricyclic antidepressants.
• Antidepressants take 4 to 8 weeks to work fully. Because PDD is chronic, treatment often continues for a year or more after improvement.

Studies suggest that combining psychotherapy and medicine is more effective for chronic depression than either alone.

For treatment-resistant cases

Augmentation with other medicines, switching medicines, transcranial magnetic stimulation (TMS), esketamine nasal spray and electroconvulsive therapy are options for severe, persistent depression under specialist care.

Self-help

• regular exercise, which reduces depressive symptoms
• a consistent sleep schedule
• staying connected with supportive people
• limiting alcohol and avoiding drugs
• setting small, achievable goals
• joining a support group

Outlook

PDD tends to be long-lasting, but treatment substantially improves mood and functioning for many people. Some reach full remission. Early treatment and continuing care reduce the risk of major depressive episodes and relapse.

Frequently asked questions

What is dysthymic disorder?

Dysthymic disorder, now called persistent depressive disorder, is a chronic form of depression with low mood on most days for at least 2 years, along with symptoms such as poor sleep, low energy, low self-esteem, poor concentration and hopelessness.

What is the difference between dysthymia and depression?

Dysthymia is a long-lasting type of depression. Major depression involves more intense episodes lasting at least 2 weeks. Dysthymia's symptoms are often milder but persist for years. Many people with dysthymia also have episodes of major depression.

Is dysthymia high-functioning depression?

"High-functioning depression" is not a medical term, but it is often used to describe dysthymia, because many people with it continue to work and meet responsibilities while feeling persistently low, tired and joyless inside.

Can dysthymia be cured?

Many people improve substantially with psychotherapy, antidepressants or both, and some reach complete remission. Because it is chronic, longer treatment and ongoing support are often needed. Even long-standing symptoms can respond to treatment.

What is double depression?

Double depression is when a person with persistent depressive disorder also experiences an episode of major depression, so a period of severe depression occurs on top of chronic low mood. It is common and responds to treatment.