School staff in Scotland missed almost 400,000 work days for mental health reasons in the last three years, new figures show.
Research obtained from a freedom of information request by the Scottish Lib Dems found teachers and support staff have taken 395,330 sick days due to mental health issues since 2015-16.
The findings reveal teaching absences have risen from 75,281 days per year to 87,066 in the three-year period.
Support staff sickness due to issues such as stress, depression, anxiety and bipolar disorder increased from 43,307 days to 58,300 by the last academic year.
Glasgow had the largest number of staff days lost in 2017-18 at 16,127, followed by Fife with 12,127 days, and the Highlands with 11,781.
A Tes Scotland investigation in 2017 also revealed that mental health problems were causing teacher absences to rise across Scotland – although it found the picture was not uniform.
The latest figures were based on responses from 29 of Scotland's 32 local authorities, with Angus, Falkirk and Moray councils not providing the information.
The Scottish Lib Dems have criticised the SNP's "baffling" education policies, with Scottish Lib Dem education spokesman Tavish Scott blaming increased pressure on teachers for the rise in sick days.
On Saturday the EIS teaching union issued a warning that even during holiday periods new technology meant teachers were increasingly expected to be “on call” and this was damaging their mental health.
Mr Scott said: "These figures show that since 2015-16 almost 400,000 staff days have been lost for mental health reasons. Year after year the number lost has risen.
"The pressure on classroom teachers is obvious. Teaching unions are worried by falling teacher morale, the top-down approach to education by central government, and the impact of testing regimes on classrooms.
"This pressure has to be a factor in the growing number of absences caused by mental ill health.
"In 2019, the Scottish Government must turn over a new leaf and work to reduce the pressure on Scotland's overworked school staff.
"Scottish Liberal Democrats will continue to demand better for our schools. That's why we are calling for a better pay deal for teachers, backed by an independent review of their conditions and the demands placed upon them, and a new package of measures to make teaching the valued and rewarding profession that it should be."
A Scottish government spokesman said: "It is important that all public sector workers providing frontline services are in the strongest position to deliver those services.
"Although it is for local authorities to ensure all of their staff, including teachers, have access to the necessary mental health and wellbeing support, our 10 year mental health strategy outlines a range of actions aimed at ensuring everyone in Scotland can get the right support when they need it most.
"We have also taken decisive action to reduce teacher workload and recruit additional teachers to avoid any additional burden on existing staff."