Many physical illnesses can cause depressive symptoms, but they generally have other symptoms and signs associated with the primary disease. Unless indicated by the patient’s history or a physical examination, blood screening need only include a complete blood count to rule out anemia and a thyroid- stimulating hormone test to rule out thyroid disease.
Other Psychiatric Disorders and Considerations
Depression shares many symptoms with other psychiatric disorders and mental health problems.
Grief and Bereavement
Depression differs from bereavement in several ways:
- symptom severity: depression involves more severe symptoms, such as psychosis and suicidality.
- reported affect: the predominant affect in grief is feelings of emptiness and loss, whereas in depression, it is depressed mood that is pervasive and persistent.
- course and duration of symptoms: dysphoria in grief decreases in intensity over days or weeks and fluctuates in pangs of grief, whereas depressed mood in depression is more persistent.
The bereavement exclusion criterion for depression has been removed in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) because grief, like reactions to other severe losses and stressors, can coexist with depression or precipitate it (American Psychiatric Association, 2013). However, persistent complex bereavement disorder can be considered when symptoms of severe grief in response to the death of a loved one persist beyond 12 months (six months for a bereaved child).
Major Psychosocial Stressors (Adjustment Disorder)
Adjustment disorders have a subsyndromal number and severity of symptoms compared with depression. Watchful waiting may be helpful to determine whether symptoms of adjustment disorder worsen or persist into a depressive episode.
Persistent Depressive Disorder (Dysthymia)
Persistent depressive disorder features depressive symptoms that last for at least two continuous years, with periods of remission lasting no longer than two consecutive months. Symptoms can be subsyndromal (in the case of dysthymia or depression in partial remission) or syndromal (meeting criteria for depression for at least two years).
It is difficult to assess for hypomania because people with bipolar disorders often do not recognize euphoric states as abnormal. A screening questionnaire can help (see “Rapid assessment”). Most people with bipolar disorders spend significantly more time experiencing major depressive episodes than hypomanic or manic episodes.
Depression is often secondary to, or comorbid with, many anxiety disorders, especially generalized anxiety disorder, social anxiety disorder and panic disorder. Anxiety is common in depression, and DSM-5 has a specifier (“with anxious distress”) to rate the severity of anxiety in patients diagnosed with depression or bipolar disorder.
Premenstrual Dysphoric Disorder
This new diagnosis in DSM-5 presents with mood swings and irritability that occur during the luteal phase of most menstrual cycles and that remit when menstruation occurs.
Substance Use and Substance-Induced Disorders
Many medications as well as alcohol and other substance use can cause a patient to present with depressive symptoms during intoxication or withdrawal.
Personality disorders, especially borderline personality disorder, usually present with lifelong patterns of mood instability. Mood episodes are typically brief and associated with stresses.