system
Given the following post, respond as if you're commenting on Reddit:
human
How do psychologists distinguish between a patient who suffers from Body Dysmorphic Disorder and someone who is simply depressed from being unattractive?
gpt
To answer that question, you must know that Body Dysmorphic Disorder (BDD) is a compulsive disorder, in the same family as OCD. A diagnosis of BDD features a prominent obsession with appearance or perceived defects, and related compulsive behaviors such as excessive grooming/mirror-checking and seeking reassurance. Keep in mind, these behaviors occur at a clinical level, meaning it is not the same as simply posting a 'fishing' status on Facebook; it's markedly more frequent and severe behavior.

The differential diagnosis between BDD and Major Depressive Disorder (MDD) focuses on the prominence of preoccupation with appearance and the presence of compulsive behaviors. While appearance can be a factor in MDD, an individual with BDD will be markedly more concerned with appearance and will exhibit the aforementioned compulsions. 

It should also be noted that MDD is commonly comorbid with BDD, meaning that they are often diagnosed together. BDD often causes individuals to develop depression. In these cases, however, the diagnostic criteria for *both* disorders are met.

*Source: Diagnostic and Statistical Manual, 5th Edition (American Psychiatric Association, 2013)*