Persistent depressive disorder, known as dysthymia or low-grade depression, is less severe than major depression but more chronic. It occurs twice as often in women as in men.
Persistent depressive disorder (PDD) is a serious and disabling disorder that shares many symptoms with other forms of clinical depression. It is generally experienced as a less severe but more chronic form of major depression. PDD was referred to as dysthymia in previous versions of the DSM.
PDD is characterized by depressed mood experienced most of the time for at least two years. In children and adolescents, mood can be irritable rather than depressed. In addition to depression or irritable mood, at least two of the following must be present: insomnia or excessive sleep, low energy or fatigue, low self-esteem, poor appetite or overeating, poor concentration or indecisiveness, and feelings of hopelessness. The more severe symptoms that mark major depression—including anhedonia (inability to feel pleasure), psychomotor symptoms (particularly lethargy or agitation), and thoughts of death or suicide—are often absent in PDD.
PDD can occur alone or in conjunction with other mood or psychiatric disorders. For instance, more than half of people who suffer from PDD will experience at least one episode of major depression; this condition is known as double depression. Compared with people with major depressive disorder, those with PDD are at higher risk for anxiety and substance use disorders.
In a given 12-month period in the U.S., PDD is estimated to affect .5 percent of people. Like major depression, PDD occurs twice as often in women as in men.
The main sign of persistent depressive disorder (PDD) is low, dark, or sad mood that occurs for most of the day, for more days than not, for at least two years. People with PDD often describe their mood as consistently sad or "down in the dumps." Other symptoms can include:
- Poor appetite or overeating
- Sleep disturbances
- Low energy or fatigue
- Low self-esteem
- Poor concentration
- Feelings of hopelessness
In PDD, these symptoms are not directly a result of a general medical condition or use of substances. In addition, they result in impaired functioning in work, social, or personal areas.
Although its exact cause is unknown, persistent depressive disorder (PDD) appears to have its roots in a combination of genetic, biochemical, environmental and psychological factors. In addition, chronic stress and trauma can provoke PDD.
Stress is believed to impair one's ability to regulate mood and prevent mild sadness from deepening and persisting. Social circumstances, particularly isolation and the unavailability of social support, also contribute to the development of PDD. This cause can be especially debilitating given that depression often alienates those who are in a position to provide support, resulting in increased isolation and worsening symptoms. In addition, trauma, loss of a loved one, a difficult relationship, or any stressful situation may trigger a depressive episode. Subsequent depressive episodes may occur with or without an obvious trigger. In old age, PDD is more likely to be the result of medical illness, cognitive decline, bereavement, and physical disability.
Research indicates that depressive illnesses are disorders of the brain. Brain-imaging technologies, such as magnetic resonance imaging (MRI), have shown that the brains of people who have depression look different than those of people without depression. The parts of the brain responsible for regulating mood, thinking, sleep, appetite and behavior appear to function abnormally. In addition, important neurotransmitters—chemicals that brain cells use to communicate—appear to be out of balance. But these images do not reveal why the depression has occurred.
Many people with persistent depressive disorder (PDD) do not get the treatment they need; in many cases because they only see their family doctors, who often fail to diagnose the disorder. Part of the problem is that people suffering from PDD believe their symptoms are an inevitable part of life. In older people, dementia, apathy, or irritability can disguise PDD. Asking open-ended questions—such as "How has your mood been recently?"—can help a physician begin to notice the signs of PDD.
Like major depression, PDD can be treated with supportive therapy that provides reassurance, empathy, education, and skill-building. Like the process of learning, which involves the formation of new connections between nerve cells in the brain, psychotherapy works by changing the way the brain functions. Certain types of psychotherapy, such as supportive therapy, cognitive-behavioral therapy (CBT), psychodynamic therapy and interpersonal therapy (IPT), can help relieve PDD. CBT helps identify and change the negative styles of thinking that promote self-defeating attitudes and behaviors. Additionally, individuals learn techniques that improve social skills and teach ways to manage stress and unlearn feelings of helplessness. Psychodynamic therapy helps patients resolve emotional conflicts, especially those derived from childhood experiences. IPT helps patients to cope with interpersonal disputes, loss and separation, and life transitions. Preliminary evidence from an ongoing NIMH-supported study indicates that IPT, in particular, may hold promise in the treatment of depressive disorders.
As with other forms of depression, there are a number of medication options for people with PDD. The most common drug treatments include selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine (Prozac) and sertraline (Zoloft), or one of the newer dual-action antidepressants such as venlafaxine (Effexor). Some patients may respond to tricyclic antidepressants such as imipramine (Tofranil). Antidepressant drugs have a number of side effects that can complicate treatment. For example, SSRIs may cause stomach upset, mild insomnia, and reduced sex drive.
For many patients, a long-term combination of medication and psychotherapy that includes a solid relationship with a mental health professional is the most effective course of treatment. Recovery from PDD can take time, and the symptoms often return. For this reason, many patients are encouraged to continue doing whatever made them well—whether it was a drug, therapy, or a combination of the two—after recovery.