I am renting a home in Missouri. I was not informed of any previous occurrences in the home, but have had instances that led me to believe there are "spirits" in the home. Investigation shows that a previous owner committed suicide in the home. Was the Landlord required by law to advise me before I accepted the property? Is this grounds to break the Lease?

No, and no. Spirits are not a legal matter.

The likelihood that someone sometime died in a home is fairly high. There is no requirement for disclosure of such things.