Diagnosis

If your doctor suspects you have persistent depressive disorder, exams and tests may include:

• Physical exam. The doctor may do a physical exam and ask in-depth questions about your health to determine what may be causing your depression. In some cases, it may be linked to an underlying physical health problem.
• Lab tests. Your doctor may order lab tests to rule out other medical conditions that may cause depressive symptoms. For example, your doctor may order a blood test to find out if your thyroid is underactive (hypothyroidism).
• Psychological evaluation. This includes discussing your thoughts, feelings and behavior and it may include a questionnaire to help pinpoint a diagnosis. This evaluation can help determine if you have persistent depressive disorder or another condition that can affect mood, such as major depression, bipolar disorder or seasonal affective disorder.

For a diagnosis of persistent depressive disorder, the main indication for an adult differs somewhat from that of a child:

• For an adult, depressed mood occurs most of the day for two or more years
• For a child, depressed mood or irritability occurs most of the day for at least one year

Symptoms caused by persistent depressive disorder can vary from person to person. When persistent depressive disorder starts before age 21, it's called early onset; if it starts at age 21 or older, it's called late onset.