Depression has its own signs and symptoms but when mixed with a personality disorder (PD) it can be more elusive. Each PD has a different manifestation of depression with varying levels of intensity. While not all depression becomes homicidal or suicidal, the risks for this possibility are presented as a word of caution. The following are the PDs most likely to raise a red flag. Anti-Social PD (Sociopath and Psychopath): This is the hardest of the PDs to diagnose as depressed unless they want a person to know about it. So accustomed to masking true feelings or emotions, they are even able to deceive themselves. At first, to counteract the sadness, they will escalate in two main ways: criminal and sexual behavior. Both behaviors have given them pleasure in the past however the acceleration and intensification of their actions will be noticeable. Just like a drug addict with high tolerance, they need much more than before to satisfy. When that fails to achieve relief, they will isolate.
Source: Trouble in the Making: Personality Disorders Mixed with Depression | The Exhausted Woman