I'm appling for an LVN/nursing program.Will a diagnosed past depression/ suicide attempt be held against me?

I don't think it would or should be. I work in mental health myself and suffer from depression and possibly bipolar disorder.
As long as you continue with treatment (if necessary) and can maintain your duties, it shouldn't be a problem.
Also, such records are supposed to be kept confidential. However, if the application asks if you've ever suffered from whatever, you may want to be honest about it.
Having a mental health issue shouldn't ban one from their chosen profession unless one's symptoms deem it necessary.
You may want to check your state's laws regarding confidentiality and licensing requirements to check if your past mental health issues can interfere with the application process. It would also be beneficial to know your state's laws in case someone does find out about your past so you can defend yourself if necessary.

You're welcome! Report It

It won't help, but it may not hurt either. What WILL hurt is being misleading about anything. If they find you lie about any history or past, even minor, run ins with the law you are out.

Those things are private and confidential. Would having cancer preclude you from acceptance. Depression is an illness just like a physical illness.
No, it should not be held against you.