How do we know the difference between a PTSD flashback and a dementia type hallucination in a patient who isn't a reliable source of information? Take for example a patient who is a Vietnam era vet- he has PTSD flashbacks and has recently developed hallucinations or possible dementia. Assuming we cannot do any invasive tests, is there a way to differentiate between the two based upon assessment and behaviors alone? Since both have differing treatment strategies, how do we figure out what is what? As a Psych NP student, I've gotten this question from the attending psychiatrist and been given instructions to "figure it out" and have been assured there is an answer. After 3 days of searching and reading, I can't find anything about a surefire way to tell between the two...and our patient can't tell us. We only have his presentation to go on.