23-year-old woman is complaining of insomnia. she states that she is unable to sleep during the day or night because she is certain the local police are watching her house and monitoring her location at all times. she began noticing different cars parked outside of her house about two months ago and realized they must be watching her. she is very organized in her speech pattern. she is expressive in describing how she tries to cleverly avoid being seen by them when leaving her home to visit her sister who lives nearby. she denies hallucinations and has no history of previous psychiatric diagnoses. what is the most likely diagnosis?