Depressive episodes are characteristic of both major depressive (unipolar) disorder and bipolar disorder. Studies show that bipolar depression is frequently misdiagnosed as unipolar depression:
- 30% of patients in a family practice setting who were determined to be depressed, anxious or both were identified as having bipolar disorder; mainly bipolar II disorder. (1)
- 56% of patients diagnosed with unipolar disorder in a primary care psychiatric sample were later found to have bipolar spectrum disorders. (2)
- In a low income primary care clinic, approximately 25% of the patients diagnosed with major depression had lifetime bipolar depression. (3)
Patient Health Questionnaire-2 (PHQ-2): The PHQ-2 screen is a 2-item self report that inquires about the frequency of depressed mood and anhedonia over the last two weeks.
- The purpose of the PHQ-2 is to screen for depression in a “first step” approach.
- The PHQ-2 includes the first 2 items of the PHQ-9.
- Patients who screen positive with the PHQ-2 should be further evaluated with the PHQ-9, other diagnostic instrument(s) or direct interview.
Patient Health Questionnaire (PHQ-9): The PHQ-9 is an instrument that screens for and diagnoses depression based on DSM-IV criteria.
- The specific items included in the scale include the 9 diagnostic criteria for making a DSM-IV depression diagnosis.
- The brevity and self-report of PHQ-9 lends itself well to clinical practice settings.
- The PHQ-9 has the potential of being a dual-purpose instrument that can establish depressive disorder and assess depressive symptom severity. The PHQ-9 can also be used in serial fashion to monitor symptoms over time.
- The PHQ-9 also has questions that screen for the presence and severity of suicidal ideation and functional impairment based on depressive symptomatology.
- Manning JS, Haykal RF, Connor PD, Akiskal HS; On the nature of depressive and anxious states in a family practice residency setting: the high prevalence of bipolar II and related disorders in a cohort followed longitudinally; Compr. Psychiatry 1997; 38: 102-108
- Ghaemi SN, Boiman EE, Goodwin FK, Diagnosing bipolar disorder and the effect of antidepressants: a naturalistic study, J. Clin Psychiatry 2000; 61: 804-808
- Olfson M, Das AK, Gameroff MJ, Pilowsky D, Feder A, Gross R, Lantigua R, Shea S, Weissman MM, Bipolar depression in a low-income primary care clinic; Am J Psychiatry, 2005 Nov: 162 (11) 2146-51