The judges ruled against two teachers
The Court of Appeal ruled that signs of stress in a worker must be obvious to their managers before the company can be taken to court for negligence.
The four cases all appeals from different county courts where judges had awarded damages for negligence after hearing how claimants had to stop work because of stress-related psychiatric illness.
Two teachers, Penelope Hatton, from Liverpool, and Leon Barber, who ran a school department in Bridgwater, Somerset, had won £90,000 and £101,000 respectively.
However, in the case of Ms Hatton, who worked at St Thomas Becket RC High School in the city, the appeal court ruled that other factors had contributed to her depression and long periods off work.
Mr Barber, said the judgement, had only reported his stress-related symptoms once he had a breakdown - and the education authority had not breached its duty of care towards him.
Disappointment
Graham Clayton, senior solicitor for the National Union of Teachers, said the union would be considering taking the two cases to the House of Lords.
He said: "We are naturally disappointed that the decision to award damages has been reversed but the Court of Appeal has now given very clear guidelines of the standards expected of employers."
"They are standards above those currently being carried out by many local authorities and we hope it will lead to the employment of procedures within local authorities to tackle the serious problem of teacher stress."
He had been awarded £7,000, but this judgement was overturned.
The cases, could set a precedent for future attempts to sue for job stress - and reduce the number of circumstances in which workers could win payouts.
However, it could make it easier for some claimants to win.
Lady Justice Hale, giving the judgement on the cases, said: "If there is no alternative solution, it has to be for the employee to decide whether or not to carry on in the same employment and take the risk of a breakdown in his health or whether to leave that employment and look for work elsewhere before he becomes unemployable."
Breach of duty
The judgement said that employers should be allowed to take what their workers say at face value and not to have to make searching enquiries about the state of their health.
It also said that there were no occupations which should be regarded as dangerous to mental health - and that bosses were entitled to assume that the employee could withstand the normal pressures of the job unless a particular vulnerability is known.
Employers, the ruling added, should only have to take action if there are plain signs of impending harm to health from job stress.
In addition, the judgement said that any employer who offered a confidential counselling service was unlikely to be found in breach of duty by the courts.
Allowing a willing worker to continue in a job was also not a breach of duty, it said, if the alternative was sacking or demotion.
In the fourth case, an award of more than £150,000 was upheld.
Olwen Jones worked at a training centre run by Sandwell District Council in the west midlands.
After complaining of excessive workload, she went off sick with depression and anxiety and never returned.
The Court of Appeal found that while there was no obvious warning of her mental state, the council had been warned of her workload concerns.
A spokesman for the Institute of Directors said: "We welcome these judgments which inject a new realism into the area of claims for stress.
"Employers are not responsible for non-work pressures on employees, and if employees are over-worked they have a responsibility to say so."
But TUC senior health and safety officer Owen Tudor said: "Unions will certainly make sure that employers know they must assess the risks of stressful occupations."