The specific revelations about global surveillance schemes that you reference like PRISM and XKeyscore are relatively recent (June 2013), so it looks like it's too early for any research to have been done into the statistical frequency of such symptoms. (I can't find any, at least!)
However, some have suggested that the common public knowledge that such programs are a reality could exacerbate symptoms in patients who already exhibit delusional narratives (eg. in schizophrenia) along these lines. A Scientific American article entitled "How Secret Spying Programs Affect the Clinically Paranoid" explains that real-life manifestations of imagined threats could interact with symptoms of psychosis. In this article, Dr. David Kimhy, Director of the Experimental Psychopathology Lab in the Department of Psychiatry at Columbia University says that though revelations about the NSA could increase general anxiety in the individual with schizophrenia, the scandal should only significantly affect those whose delusions mirror the news.
However, he goes on the say it could instead lessen such delusions:
“The thought that the government is following everyone, in a paradoxical way, may take away from the delusion,” says Kimhy. Individuals with persecutory delusions usually feel that they are unique targets; thus, the broad net of surveillance that is so troubling to the NSA’s critics might reduce feeling of persecution in an individual who previously believed the government was only after him. Indeed, the therapist might use this broadness as a context in which to discuss the patient’s delusions. “You could ask, ‘What’s so unique to you? What special powers do you have? And by the way, why don’t we talk about those special powers,’” says Kimhy.
This is echoed in the writing of psychologist Daniel Freeman in the journal Clinical Psychology Review:
The more a belief is implausible, unfounded, strongly held, not shared by others, distressing and preoccupying then the more likely it is to be considered a delusion.
Even prior to these recent revelations, it is well established that current events can impact delusional symptoms. A study published in the journal Cognitive Neuropsychiatry, "The Truman Show Delusion: Psychosis in the Global Village" concluded that "although schizophrenia and bi-polar disorder have existed in many different cultures and times, their character and means of expression are highly influenced by the culture the patient comes from, as well as its contemporary technology."
An example of mental health symptoms being culture-sensitive was given recently in a TV documentary series about South London and Maudsley Hospital for mental health. A member of staff explained that in the '80s, when AIDS was heavily featured in the news, patients with Obsessive Compulsive Disorder frequently showed concern about contamination, worrying that spots of ketchup in a kitchen were blood and similar. He said that this is less common now, when AIDS is in the media less, but they've recently seen an increase in patients having intrusive thoughts that make them worry they are a paedophile, as there have been some high-profile child abuse cases in British media reently.