Nick Alston, Essex’s police and crime commissioner, believes one in-five incidents have a mental health-related element.
The force has agreed a scheme with the North Essex NHS Partnership Foundation Trust to give officers better training.
A spokesman for the trust said: “We have recently agreed a scheme where new officers will come to us on three-day placements to better understand mental health services and the illnesses people experience.
“Our work together includes where people with mental illness experience crimes themselves or suffer hate crime, as well as offending behaviour.
“We must always do what is right for the person and the community.
“Sometimes, that balance is hard to strike and that’s why good liaison with the police is essential.”
A study carried out by Staffordshire’s police commissioner revealed about 20 per cent of incidents there had a mental health-related element.
Mr Alston said, from discussions with officers, he believes figures in Essex are about the same.
He said: “It is a real worry, a really challenging issue.
“This has been the most difficult issue to get to grips with and is proving the most elusive. This is the area we have made the least progress in.”
Examples of the difficulties police face include people being brought into custody who act aggressively.
At least ten vulnerable individuals have died in the UK in recent years after police restraint, according to charity Inquest.
Last year, Essex Police detained 621 people for their own safety and the safety of others and 200 were subsequently admitted for mental health care.
Mark Smith, chairman of the Essex Police Federation, said dealing with mental health-related incidents is a major problem for officers.
He said: “Vulnerable people need one-to-one policing and the resources are not there for it.
“There are people being put in cells which are simply not the right place for them.
“Her Majesty’s Inspectorate of Constabulary is bringing out a report soon to highlight the scale of the problem.”