Answered by Steve, Hiring Expert at Caterpillar Inc., on Friday, November 7, 2014
If your mental illness does not impact your ability to do your job, then you are not obligated to disclose it. If, however, you will require a reasonable accomodation to perform your job, then yes you should disclose it, as your employer will be required under the Americas With Disabilities act to provide that reasonable accomodation. Regarding the timing of disclosing, should you choose to do so, most likely that opportunity will present itself to you on or around your first day when you complete new hire paperwork. If, however, the disability will impact your ability to interview, then disclose it at that time. In general, however, you should not be afraid to disclose it as there are legal requirements that prohibit an employer from discriminating against you because of a disability.