This patient's presentation is consistent with a diagnosis of persistent depressive disorder (DSM 5) or dysthymia (DSM-IV), which by definition, must be present for at least two years.
Chronic depressive disorder or dysthymia are persistent forms of subclinical, mild depression that, by definition, last for at least 2 years with symptoms present for the majority of days and no period longer than 2 consecutive months without symptoms. Dysthymia is considered a mood disorder as opposed to a personality disorder, despite patients often claiming that they simply have a "depressed personality" to explain the long-term nature of their symptoms. To be diagnosed with dysthymia or chronic depressive disorder, the patient must NOT have any major depressive episodes in the two year period, must NOT have any episodes of hypomania which would be more consistent with cyclothymia, and retain generally normal function despite depressed mood.
Maurer discusses screening strategies in adolescents and adults, concluding that the Patient Health Questionnaire 2 (PHQ-2) should be used as a first-line tool due to its relatively high sensitivity in detecting depression. If this initial PHQ-2 screen is positive, then PHQ-9 should be administered due to its greater specificity. If this screening algorithm is positive, further evaluation is still necessary to confirm that the patient meets the diagnostic criteria for depression.
Komossa et al. conducted a Cochrane review on the role of second generation antipsychotics in the treatment of major depressive disorder and dysthymia. They conclude that, when used to augment SSRI therapy, second generation antipsychotics, including quetiapine, aripiprazole, olanzapine, and risperidone, showed beneficial effects over placebo in the treatment of dysthymia and major depressive disorder.
Illustration A depicts a table comparing and contrasting dysthymia and major depressive disorder.
Answers 1, 2, 3, and 5: Dysthymia (encompassed under the heading of chronic depressive disorder in DSM-5), by definition, consists of symptoms lasting for at least 2 consecutive years.
Maurer DM. Screening for depression. Am Fam Physician. 2012 Jan 15;85(2):139-44.
PMID:22335214 (Link to Abstract)
Komossa K, Depping AM, Gaudchau A, Kissling W, Leucht S. Second-generation antipsychotics for major depressive disorder and dysthymia. Cochrane Database Syst Rev. 2010 Dec 8;(12):CD008121. doi: 10.1002/14651858.CD008121.pub2. Review.
PMID:21154393 (Link to Abstract)