Almost two-thirds (64%) of teachers in Scotland say their mental health has suffered because of their work in the last year.
In a survey by the NASUWT teaching union, 44% said they have sought medical help as a result.
While 78% said workplace stress has increased over the last 12 months.
One in 10 teachers said they have been prescribed antidepressants, while 7% revealed they are increasingly reliant on prescription drugs.
Meanwhile 54% said their job satisfaction has decreased in the last year, with 55% having seriously considered quitting the profession.
NASUWT general secretary Chris Keates said: “It is clear that the mental and physical health of too many dedicated and talented teachers is being broken by the pressures of excessive workload, violence and indiscipline from pupils and management bullying.
“Many teachers are walking away from the profession to salvage their health and family relationships, and this in turn is understandably deterring new recruits from choosing a career in teaching.”
A total of 673 NASUWT members in Scotland took part in the online survey, with the results being released as its conference gets under way in Glasgow – with mental health problems high on the agenda.
According to the research, 75% of teachers have been affected by anxiety in the last 12 months because of their job, with 83% suffering sleeping problems.
Just over a fifth (21%) said they are drinking more alcohol, almost one in 10 (9%) has seen their relationship break down, and 2% have self-harmed.
Ms Keates said union leaders are “acting on teachers’ concerns”, saying the NASUWT has launched a trade dispute with employers and Deputy First Minister John Swinney.
It wants a “new deal” for teaching staff which addresses the issues “driving the growth in stress and mental ill health amongst the profession”.
Jane Peckham, NASUWT national official for Scotland, said: “Too many schools have become toxic environments to work in, where constant pressure, bullying and unsustainable workloads are making teachers mentally and physically ill.
“Action to address this must start at the top. The solutions to begin to alleviate this issue are there but they need statutory force and concerted attention from ministers and employers to make sure teachers feel empowered and supported at work, not broken and exhausted.”
Liberal Democrat education spokesman Tavish Scott said: “These teachers’ accounts of the impact the job has had on their wellbeing are frankly horrifying.
“There are real questions for the Government when two-thirds of teachers are seeing their mental health suffer because of the pressures of work.
“We already face a recruitment and retention crisis. This shows that teachers are under too much pressure, burdened by the workload and having lost critical classroom support.”
Education Secretary John Swinney said: “No teacher should feel like their job adversely affects their mental health.
“Wellbeing is an issue that affects us all, should be taken seriously and these figures are therefore extremely worrying.
“We are already taking a range of actions to put in place additional support for teachers to improve recruitment and retention rates, improve teachers’ pay and tackle workload wherever possible.
“Our work with teachers and teaching organisations will continue to identify where there is action we can take to improve the daily lives of teachers.”