If you're a manager, what do you honestly think of staff going off on mental health sickness?

Depends. Your child/very close relative dies. Understandable. Anything else I’d say they don’t have much resilience.

An employee doesn’t usually work in isolation so it’s often the case that their colleagues have to cover/pick up the slack of the absentee. That’s what’s most galling.

I’d find their absence irritating.

I have managed people and I had one report who regularly took days sick here and there claiming migraines which it later transpired were triggered by poor mental health.

It went on on and off over a period of about two years. She was eventually let go after repeatedly being warned about it. The company offered her to take s reset sabbatical of a month (paid) and then a staggered return to work and she said she didn’t want or need it but she continued to take roughly two days a month off due to “migraines”.

By contrast another colleague had a mental health crisis and burned out and was given three months unpaid leave to recover. People were extremely supportive when she returned.

I think honesty and clarity with people are being purposeful about how you will address it go a long way. I have huge respect for the second colleague, less for the first. I understand there was stigma etc but this individual wasted a huge amount of other people’s time and energy while the second managed in a minimally disruptive way.

Depends on your role within the organisation.

Commander of a Nuclear Submarine, probably think you aren't best suited to the role.

Shift manager at my local Asda, probably hope you signed off my leave before went on the sick.

If the employee is genuinely unwell then there is no problem.
I think they'd be more annoyed by staff who call in sick regularly.
It happens we're human.
It's important that they support the team as it can breed resentment if they are overloaded.