Depression: Differential diagnosis
Many medical illnesses can cause depressive symptoms, but they generally have other symptoms and signs associated with the primary disease.
Unless indicated by history and/or physical examination, screening blood tests need only include complete blood count and thyroid stimulating hormone test (to rule out anemia and thyroid disease).
Patients who take certain medications or who use alcohol or other drugs can present with depressive symptoms.
Grief and major psychosocial stressors (adjustment disorders)
Major depressive episode (MDE) can be differentiated from bereavement by the severity of symptoms (e.g., psychosis or suicidality), the presence of anhedonia (total loss of feelings of pleasure) and the duration of impairment (longer than two months).
Adjustment disorders have subsyndromal number and severity of symptoms compared to MDE. Watchful waiting may be helpful to determine whether symptoms of adjustment disorder worsen or persist into a depressive episode.
It is difficult to assess for hypomania because patients often do not recognize euphoric states as abnormal. Using a screening questionnaire is helpful.
Depression is often secondary to, or comorbid with, many anxiety disorders, especially generalized anxiety disorder, social anxiety disorder and panic disorder.
Personality disorder (especially Cluster B)
Personality disorders usually present with lifelong patterns of mood instability.
Major depressive disorder in adults: Diagnosis and management (BC Guidelines, 2013)
Depression in adults: Recognition and management (Nice guideline CG 90, 2009)
Depression in adults with chronic physical health problems: Recognition and management (NICE guideline CG91, 2009)
Depression in children and young people: Identification and management (NICE guideline CG28, 2005)