Cases of UK police officers and staff taking long-term sick leave for psychological reasons have risen by 35% over the last five years, statistics obtained by BBC Radio 5 live suggest.
The figures, released under the Freedom of Information Act, show cases rose from 4,544 in 2010-11 to 6,129 in 2014-15 despite police workforces shrinking.
There was also a steady increase in overall long-term sick leave.
The government said policing was "stressful" and forces must help staff.
The BBC's 5 live Daily programme contacted 46 police forces across the UK, and 40 provided information.
Data showed the number of police employees on long-term sick leave - defined by forces as either 28 or 29 days or more - rose from 19,825 in 2010-11 to 22,547 in 2014-15.
West Yorkshire Police recorded the largest rise in long-term sick leave over a year - up 44% between 2013-14 and 2014-15 - from 521 days to 748.
Warwickshire Police showed the biggest decrease of 17% over the same time period.
Che Donald, of the Police Federation, which represents officers up to the rank of chief inspector, said there had been "unprecedented cuts to police officer numbers" while demand on forces had not decreased.
He said increased sickness - including for psychological reasons - was not surprising as officers often worked in "highly stressful fast-moving environments" and were exposed to "horrific situations".
"This, coupled with a reduction in resources and manpower, can lead to the perfect storm," he said.
Policing minister Mike Penning said: "Policing, by its very nature, is a stressful and demanding job and it is the responsibility of chief officers - with help from the College of Policing - to ensure that police officers and staff are supported in their work."
He said the government allocated £10m in 2014 to help emergency services staff through "mental health, physical recuperation and bereavement support".
Police Scotland could not provide information for the full five years requested by the BBC so the figures do not include Scotland - but last year data suggested more than 53,000 working days had been lost in the force over two years due to stress.