Psychological Thriller Genre

Psychological – Elements that are related to the mind or processes of the mind
Thriller – A genre of fiction that attempts to "thrill" its audience by placing characters at great risk.
Psychological + Thriller – By combining these two terms, the definition changes to a narrative that makes the characters exposed to danger on a mental level rather than a physical one. Characters are no longer reliant on physical strength to overcome their brutish enemies (which is often the case in typical action-thrillers), but rather are reliant on their mental resources.
 
The suspense created by psychological thrillers often comes from two or more characters preying upon one an other's minds, either by playing deceptive games with the other or by merely trying to demolish the other's mental state.
 
Stream of consciousness - a literary technique which seeks to describe an individuals point of view by giving the written equivalent of the character's thought processes. In psychological thrillers, the narrative tries to manifest the character's psyche through word usage, descriptions, or visuals.

First-person narrative - a literary technique in which the story is narrated by one or more of the characters, who explicitly refers to him or herself in the first person. This direct involvement that the characters have with the story in turn makes the reader more involved with the characters themselves, and thus able to understand the mechanics of the characters' minds.
Back-story - the history behind the situation at the start of the main story. This deepens the psychological aspect of the story since the reader is able to more fully understand the character; more specifically, what the character's motivations are and how his past has shaped his current cognitive perceptions.