What's your psychiatric diagnosis?

Employer. But in my country the employer isn't allowed to see the reason you're sick. It's not on their copy of the sick note. You do have to see an independent 'work doctor' at the start of your contract and at some other points though, who will deem you fit or unfit to work. Whether you're fit or unfit to work is all the employer is entitled to know - in theory. In reality people get curious and want to know why they're having to cover your work, and 'work doctors' just blithely sign the 'fit to work' coupon the moment you walk through the door, without asking any questions.