If it's a large company and you initiate the process through HR, as you have done, you *should* be okay, but state laws vary. Sometimes you have to use the mental health benefit offered by your company for counseling, then the counseling refers you to rehab. Also, it is a business and they have the right to fill your existing position if necessary to achieve business results. I mean, it's not a charity after all. The work has to get done. So you may come back to find another position being offered, but considering the alternative (no job at all) it may be reasonable. It often depends on the type of job, the business, your relationship with your boss, your seniority, their investment in you, etc. And how much pain you have already caused them. Good luck with it!