According to the DSM-IV, a diagnosis of mood disorder cannot be made if the cause is believed to be due to "the direct physiological effects of a substance"; when a syndrome resembling major depression is believed to be caused immediately by substance abuse or by an adverse drug reaction, it is referred to as, "substance-induced mood disturbance".
Depression and other mental health problems can have a substance induced cause; making a differential or dual diagnosis regarding whether mental ill-health is substance related or not or co-occurring is an important part of a psychiatric evaluation.