Plymouth police have been called to the city's specialist mental health unit 460 times in five years - 270 of them to deal with missing people.
The figures have been released to the BBC after a freedom on information request.
The Police Federation said dealing with people with mental health problems was putting a strain on their services.
The police have been alerted to 700 incidents in five years at the Derriford unit.
According to the BBC incidents include one allegation of rape, 13 sexual...
