Clinical depression
Clinical depression (also called major depressive disorder, or sometimes unipolar when compared with bipolar disorder) is a state of intense sadness, melancholia or despair that has advanced to the point of being disruptive to an individual’s social functioning and/or activities of daily living. Although a low mood or state of dejection that does not affect functioning is often colloquially referred to as depression, clinical depression is a clinical diagnosis and may be different from the everyday meaning of “being depressed.” Many people identify the feeling of being depressed as “being blue,” “feeling sad for no reason”, or “having no motivation to do anything.” One suffering from depression may feel tired, sad, irritable, lazy, unmotivated, and apathetic. Clinical depression is generally acknowledged to be more serious than normal depressed feelings. It often leads to constant negative thinking and often substance abuse.
Without careful assessment, delirium can easily be confused with depression and a number of other psychiatric disorders because many of the signs and symptoms are conditions present in depression, as well as other mental illnesses including dementia and psychosis