Editing Major depressive disorder (section)

===Differential diagnoses===
{{Main|Differential diagnoses of depression}}

To confirm major depressive disorder as the most likely diagnosis, other [[Differential diagnosis|potential diagnoses]] must be considered, including [[dysthymia]], [[adjustment disorder]] with depressed mood, or [[bipolar disorder]]. Dysthymia is a chronic, milder mood disturbance in which a person reports a low mood almost daily over a span of at least two years. The symptoms are not as severe as those for major depression, although people with dysthymia are vulnerable to secondary episodes of major depression (sometimes referred to as ''[[double depression]]'').<ref name=Sadock552/> [[Adjustment disorder|Adjustment disorder with depressed mood]] is a mood disturbance appearing as a psychological response to an identifiable event or stressor, in which the resulting emotional or behavioral symptoms are significant but do not meet the criteria for a major depressive episode.{{sfn|American Psychiatric Association|2013|p=168}}

Other disorders need to be ruled out before diagnosing major depressive disorder. They include depressions due to physical illness, [[medications]], and [[substance use disorder]]s. Depression due to physical illness is diagnosed as a [[Mood disorder#Due to another medical condition|mood disorder due to a general medical condition]]. This condition is determined based on history, laboratory findings, or [[physical examination]]. When the depression is caused by a medication, non-medical use of a psychoactive substance, or exposure to a [[toxin]], it is then diagnosed as a specific mood disorder (previously called ''substance-induced mood disorder'').{{sfn|American_Psychiatric_Association|2013|p=167}}