stylistic:tone, stylistic:style_transfer, structural:summarization, structural:expansion
Differential diagnosis

The occurrence of narcissistic personality disorder presents a high rate of comorbidity with other mental disorders. People with a fragile variant of NPD (see Subtypes) are prone to bouts of psychological depression, often to the degree that meets the clinical criteria for a co-occurring depressive disorder. NPD is associated with the occurrence of bipolar disorder and substance use disorders, especially cocaine use disorder. NPD may also be comorbid or differentiated with the occurrence of other mental disorders, including histrionic personality disorder, borderline personality disorder, antisocial personality disorder, or paranoid personality disorder. NPD should also be differentiated from mania and hypomania as these cases can also present with grandiosity, but present with different levels of functional impairment. It is common for children and adolescents to display personality traits that resemble NPD, but such occurrences are usually transient, and register below the clinical criteria for a formal diagnosis of NPD.