If i am submitted into the er for an intentional overdose, can i be forced to go to the mental hospital?

That might be a possible outcome, but there is no way to accurately answer without a lot more information. It depends on medical and psychiatric evaluation at the time, hospital policy, and laws that vary widely from one state to the next. If you are considering overdosing or other self harm, PLEASE go voluntarily for help, call a mental health hotline, or speak with your loved ones. Good luck.

Depending on the psych and medical assessment you might be committed to a psych ward if so determined.

If medical assessment indicates that you are a risk to yourself or society, you could be committed to a mental hospital, usually through a court order. Do not let this possibility deter you from getting treatment that you may need to save your life and protect your health. Wish you good health!