Staff absences for mental health problems have doubled at hospital trusts across England in the past four years.
Figures obtained by the BBC revealed 41,112 staff were off sick with anxiety, stress and depression in 2014 – up from 20,207 in 2010.
NHS England said it needed to do more to support staff.
The Royal College of Nursing said the figures reflected the “relentless pressure” staff were under.
The NHS employs 1.25 million people across all of its services throughout the country.
A spokesman for the NHS said: “Our staff are some of the most hard-working and dedicated people in our country.
“We now have record numbers of nurses and other front-line professionals, but the NHS needs to become better at supporting staff – not least because better staff experience leads to better patient care.”
NHS Employers, the organisation which represents its managers, added it was doing more to support staff.
Tim Baggs, from the Royal College of Nursing, said a staff survey conducted by the NHS five years ago revealed high levels of stress among medical staff.
“These [new] figures are a real cause for concern to us but they don’t give us any surprises.
“They really do mirror what we have been hearing from our members and staff surveys about the relentless pressure that nursing staff are under.
“We had what should have been a seismic report five years ago into the health and well-being of NHS staff which recommended that trusts should do more.
“Some have done that but clearly these figures suggest trusts could be doing better.”
Emma Mamo, from mental health charity Mind, said there had been funding cuts of about 8% to NHS services with 3,000 nursing posts lost.
“These figures could suggest sickness absence relating to mental health problems is on the rise among hospital staff.
“The impact of these cuts, through increased workloads and changes to services, is bound to have an impact on staff morale and wellbeing.
“It’s vital that hospitals put in place measures to help promote good mental health at work for all staff.”
Nearest tube: Elephant & Castle underground station (Northern and Bakerloo lines).
Nearest Railway Station: Elephant & Castle
Buses from Elephant and Castle: ask bus driver for Burgess Park. Bus numbers: 12, 171, 148, 176, 68, 484, 42, 40, 45