The main reason for sickness absence in the London Fire Brigade is now stress, anxiety and depression, Commissioner Dany Cotton has said.
LFB has seen a "small increase" in the number of days taken off as sick leave over the last three years, Ms Cotton, the brigade's most senior firefighter, said.
It is the first time mental health has been the leading cause of the absences, she told the London Assembly on Thursday.
LFB employed four extra counsellors following the Grenfell Tower disaster on June 14 last year, which led to the deaths of 72 people, taking the total number to nine.
There have been small increases in the number of days we've lost due to sickness absence in the last three years, with the leading cause now for the first time being stress, anxiety and depression
LFB's counselling and trauma team has treated more than 157 personnel since the fire, according to a document submitted to the public inquiry which sets out changes the brigade has made since the blaze.
Staff have been treated for adverse trauma response and/or post-traumatic stress disorder as they "deal with the traumatic impact of the fire and process of giving 'oral' evidence at the Grenfell Tower inquiry".
Some 80 fire officers - from a firefighter still on probation to the Commissioner - have given oral evidence during the first phase of the probe, with dozens of extensive written statements also submitted.
At times, staff have found it painful to relive the harrowing night, with several witnesses breaking down as they addressed the hearing.