Dysthymia

Dysthymia, also called persistent depressive disorder (PDD) in the DSM-5-TR and dysthymic disorder in the ICD-11, is a psychiatric condition. Its symptoms resemble those of major depressive disorder, but they last much longer: at least two years in adults and one year in children.

The term dysthymia was introduced in the late 1970s by Robert Spitzer, replacing the earlier concept of "depressive personality." When the DSM-5 came out in 2013, the condition was renamed persistent depressive disorder, having been called dysthymic disorder in the DSM-IV. The ICD-11 still uses the older name. PDD is defined by a two-year history of major depression symptoms that are not better explained by another health condition, along with significant distress or trouble functioning.

Because the disorder is chronic, people may have symptoms for years before getting a diagnosis—if they ever do. They might see their low mood as part of their personality or character, not as a medical issue, and never bring it up with a healthcare provider. PDD now includes what earlier DSM editions called chronic major depressive disorder and dysthymic disorder. This change was made because research has not found a clear, clinically meaningful difference between the two.

**Signs and symptoms** Dysthymia involves a depressed mood lasting at least two years, plus at least two of these: poor appetite or overeating, sleeping too much or too little, low energy or fatigue, low self-esteem, trouble concentrating or making decisions, and hopelessness. In children, irritability may be more noticeable than sadness.

Mild cases can lead people to avoid stressful activities and opportunities where they might fail. In more severe cases, people may withdraw from daily life and find little pleasure in things they used to enjoy—a symptom called anhedonia. Diagnosis can be tricky because symptoms are subtle, and patients often hide them in social situations. Dysthymia also frequently occurs alongside other conditions, such as anxiety disorders, substance use disorders, and personality disorders, and suicidal thoughts are common.

**Causes** No single biological cause applies to all cases, suggesting the disorder has diverse origins. There is some evidence of a genetic predisposition: in families of people with dysthymia, the rate of depression can be as high as 50% for the early-onset form. However, more recent studies suggest that family environment and non-shared environmental factors play a bigger role than genetics or neurobiology. The uncertainty about biological causes partly stems from a lack of genetic and neurobiological research, including genome-wide studies with small sample sizes. Other factors linked to dysthymia include stress, social isolation, and lack of social support. A 1998 twin study found that identical twins were no more likely than fraternal twins to both have dysthymia, supporting the idea that there is no consistent genetic basis.

**Co-occurring conditions** Dysthymia often occurs with other mental disorders. When someone has episodes of major depression on top of dysthymia, it is called "double depression." If moods alternate between dysthymic and hypomanic periods, that points to cyclothymia, a mild form of bipolar disorder. At least three-quarters of people with dysthymia also have a chronic physical illness or another psychiatric condition, such as an anxiety disorder, cyclothymia, drug addiction, or alcoholism. Common co-occurring conditions include major depression (up to 75%), anxiety disorders (up to 50%), personality disorders (up to 40%), somatoform disorders (up to 45%), and substance use disorders (up to 50%). People with dysthymia have a higher-than-average risk of developing major depression. A 10-year follow-up study found that 95% of dysthymia patients had an episode of major depression. When that happens on top of existing dysthymia, it is called double depression.

**Double depression** Double depression is hard to treat because patients often see the major depressive symptoms as a natural part of their personality or as something beyond their control. This acceptance can delay treatment. Even if they seek help, treatment may not work well if it only addresses the major depression symptoms and ignores the underlying dysthymia. People with double depression tend to report significantly higher levels of hopelessness than those with only dysthymia or only major depression. This gives mental health providers a useful baseline for diagnosis and a symptom to focus on during treatment. Cognitive therapies can be effective for helping people with double depression change negative thinking patterns.