Yes, you would have to disclose the diagnosis, at least in general terms (i.e. you don't necessarily need to go into all details):1) First, the doctor has no authority over the employer; the employer is not required to simply accept the doctor's recommendation at face value without inquiring into the facts, condition, issues, etc.2) Second, your rights and the employer's obligations depend in large part on the nature and severity of the condition, and also whether or not it can be traced to some injury at work; the employer therefore needs to know, and has a right to know, what the condition is, so it can comply with its obligations under the law.