Hundreds of working days were lost at Suffolk’s largest hospital through psychological issues last month, prompting an investigation into the possible link between staff overtime and stress.

Ipswich Hospital reported a “continuing trend” of illnesses such as anxiety and depression being the biggest cause of absence among its employees.

According to a report prepared for today’s hospital trust board meeting, 750 full-time equivalent days – more than two years – were lost to psychological issues in June alone.

The hospital also says it has been “exceptionally busy” coping with staff shortages resulting in employees volunteering – or being asked – to work extra hours.

Health chiefs are now investigating whether there is a link between the extra working hours and “high levels of stress”.

Although overall staff absences have fallen at the hospital, and are lower than national averages, psychological issues have consistently been the biggest cause of days lost through illness over the past year. The total peaked at 987 days in December, but has been reported as a “continuing trend” in subsequent board papers.

Mark Porter, the British Medical Association’s council chairman, said “relentless pressure and chronic under-resourcing” have left many doctors “stretched to breaking-point.”

“Unmanageable workloads coupled with a target-obsessed culture is contributing to ill health among healthcare staff,” he added.

Unison regional organiser Cheryl Godber said government policy was pushing more trusts, like Ipswich, into staffing difficulties.

“However it is pleasing to note that Ipswich Hospital is at least taking this issue seriously,” she added.

According to the latest NHS England survey, 72% of staff at the hospital said they worked extra hours and 32% said they experienced work-related stress in the past year – similar to the national average.

A hospital spokesman agreed many roles in the hospital could be stressful but said the trust had a “strong focus on wellbeing”.

“We very much recognise that we want everyone to be as well as they possibly can be and it is a major focus for us,” the spokesman added.

Although the hospital acknowledged staff had been working extra hours, due to shortages, it was “within a framework which is allowed”.

“We are not asking anyone to do more than is safe,” the spokesman added. “We need to question, identify and understand whether the stress is linked to additional hours that they have worked.

“That conclusion has not been reached – it is still ongoing.”

Overall, the hospital compares favourably to other NHS organisation, for absence rates, the spokesman added.

The latest overall absence rate for the hospital in June was 3.35%, compared with 4.06% last year.

Figures from the Health and Social Care Information Centre show the overall absence rate for 2015/16 at Ipswich Hospital was 3.46%, or 42,987 days. Across the NHS as a whole, the figure was 4.37%, with the highest rate of a absence recorded among ambulance trusts at 5.79%.

NHS England said it had introduced a £450million financial incentive for trusts to offer wellbeing programmes, including £150m for mental health schemes.

“Improving the health and wellbeing of staff working in the NHS is a top priority,” a spokesman added.