It depends on the job, but generally speaking if you have a disability or health condition you are not obliged to share this with your employer.
However, it is usually better to be honest with them so that they can support you and generally be more understanding if issues arise.
I would not inform them at interview but if you are offered the job you may wish to mention it then and notify them of any reasonable adjustments you may require.
By the way, do you have any support from a mental health charity? Some of them have employment advisers who can help you with thing