Most Northern Ireland Ambulance Service paramedics are suffering sleep problems and mood swings because of the "dangerously high" level of workplace pressure, a survey has found.
Long hours, staff shortages and the demands of the job place an enormous burden on staff, according to health workers' union Unison.
The review said 96% suffered from stress and two-thirds had to take time off sick.
Unison regional organiser Nuala Conlon said: "Working in emergency services is stressful but the pressure on ambulance staff is reaching dangerously high levels."
The survey of 248 ambulance workers in Northern Ireland revealed 71% were suffering sleep problems, 73% felt irritable as a result and experienced mood swings, and 64% had anxiety.
Many had to take time off sick because of work-related stress and a further fifth admitted they were very close to doing so, it found.
One paramedic described how hospital closures meant they had to drive hundreds of miles every day. He said: "Too few ambulances and missed meals would stress anyone."
Another who has not taken a day off sick in 10 years said he is about to "explode". Others described being tearful, suffering migraines, post-traumatic stress disorder and feeling exhausted.
Ms Conlon said: " It is unacceptable that the current system doesn't allow for proper breaks between shifts.
"Higher call-out rates and lengthy waits outside A&E departments are adding to the problem. It is clear that the pressure caused by government funding cuts is having a huge impact on staff and on patient safety."
She said it was vital that patients use the service responsibly, only calling 999 for an ambulance when there is a real emergency.
The survey showed much greater pressure on staff in the ambulance service than any other part of the NHS, Ms Conlon said.
"The pressure on workers is mounting and the apparent lack of support from their employers means they are suffering in silence," she said.
"Year after year the levels of stress remain unacceptably high and yet neither employers nor the government have done anything to address this."
Ambulance workers responding to the survey claimed their concerns had fallen on deaf ears when raised with managers.
One said: "Work is becoming an endurance test, it is physically and mentally draining and if you tell management of your concerns you are told to your face 'if you don't like it there are plenty of people who are happy to take your place'. So we're beat before we start.
"The stress is appalling. At times I am sicker than the patients and my managers have no interest in their staff."