Mugging victims are paranoid for months after suffering a physical assault, says a new study. That might be apparent if you've ever been attacked while traveling, but the newly quantified results could make therapy for victims more effective.

Previous research had established that physical assaults can lead to post-traumatic stress disorder (PTSD) in victims, but according to the researchers, this is the first study to investigate paranoia after mugging attacks.

"Traditionally it was thought paranoid thinking was rare in the aftermath of an attack," said Professor Daniel Freeman of the University of Oxford, who led the study, in a news release. "It was thought that paranoia only occurred in severe cases of PTSD. However, fears about other people may well actually be typical."

The study researchers tracked 106 people over the course of six months after they suffered minor injuries from a physical assault. During that period, psychologists regularly monitored the participants for symptoms of paranoia and PTSD using self-report questionnaires, clinical interviews, and a virtual reality test that measured how participants reacted to emotionally neutral characters on a computer.

The results showed that a whopping 80% of the assault victims reported that they were more fearful of other people than they wanted to be.

Their paranoia tended to generalize to all people around them- two thirds of the participants said they were now afraid of all males, and half said they were now wary of all females. Many were even afraid of the virtual reality characters.

"It is very understandable that being attacked makes us wary of the people around us," said Freeman in the news release. "Our mindset may become more like that of a bodyguard, vigilant for danger."

Freeman went on to say that being overly mistrustful is a form of paranoia that can isolate people, leading them to think of the worst at all times even in the absence of a real threat. It may be useful to think that way in the short term after an attack, but long-term hypervigilance can be draining.

Several factors strongly correlated to paranoid feelings six months after an assault: being attacked in familiar places, feeling defeated during the incident, feeling unsupported by others, and trouble sleeping.

According to Freeman, sleeping well and feeling supported by those close to you are important parts of emotional recovery from assault.

The researchers hope that their research can lead to improved cognitive-behavioral therapies for assault and mugging victims.

"During the last decade, significant progress has been made in understanding the factors that predict who will develop PTSD after assault," said Professor Anke Ehlers, a PTSD expert at the University of Oxford who coauthored the study, in the release.

"The finding that many of these factors also predict paranoia opens up new avenues for treatment."

The study, funded by the Wellcome Trust, was published today in the journal Psychological Medicine.