The cameras also haven't changed the typical number of complaints the force gets against police.
The study tracked the effectiveness of 56 cameras worn by officers as part of a three-year pilot project.
It says the cameras were useful in investigations, but also caused officers to hesitate about using appropriate force against suspects.
The study says the cameras were just as likely to escalate a person's behaviour than to subdue it.
Police say cameras will not be provided to all officers, but will be worn by those involved in high-risk interactions with the public.