One characteristic of all workers' compensation systems is that the employee is only required to demonstrate that the injury or illness was work related.
Like the Civil Rights Act of 1964, the OSH Act permits individual states to establish and manage their own safety and health programs for the private sector.
An employee with a mental illness that can be shown to have a connection to the nature of his employment would not be eligible for workers' compensation.
Whistleblowers are not protected against retaliation for filing an OSHA complaint because the OSH Act contains no language in regards to whistleblowers at all.
The exclusivity principle would apply to a situation where an employer told his employee to ignore a safety procedure, and in doing so the employee was injured.
Prior to the enactment of workers' compensation statutes, the only recourse for injured workers was to sue their employers for damages under state tort laws.