In the area of mental health, the obligations of employees really are to not treat their employees less favourably because of a mental health condition. For any employee, their obligation really is to allow the employer to give them and their colleagues a safe working environment.
There's no obligation on an employee to disclose if they have a mental health condition, unless it effects their ability to perform in their role, or it effects their safety or the safety of others in the workplace.
An employee has the right to have information about their mental health condition kept confidential from their colleagues and that right comes out of the privacy act. And so, an employee should be careful to advise their employer how they wish the information to be used when they disclose their mental health condition.
An employee with a mental health condition has an obligation to their colleagues insofar as they have to protect the safety of their co-workers. So, if their condition might affect the safety of their co-workers, there is an obligation to disclose that condition.
An employer has an obligation to provide a safe working environment to all employees. So, they're only entitled to be told about a mental health condition where it might have an effect on that employee's safety or the safety of other employees. An employer is required to modify the working environment of an employee with a mental health condition although it's only required to make reasonable accommodations with thought for the needs of the business. So, it wouldn't be required to make extremely costly or impractical modifications.
As far as workplace health and safety laws are concerned, mental health of employees is treated in a similar way to physical safety and workplaces should have regard to both.
Leaving aside the legal obligations of an employee and an employer, in our experience, it's important when dealing with a mental health condition in the workplace that the individual and the business work together to their mutual benefit, so that the individual can give their valuable service, but also so that business can get value from that person.