It was put on this earth as a medicine by God. I don't think he makes mistakes but I have been wrong before. It has been used for thousands of years as a medicine. Remember what God told Adam and Eve in the Garden? He put all the plants and animals on this earth for their use and gave them dominion over such plants and animals. He did however tell them not to eat that darned apple and being recalcitrant children they ate it anyway. Nothing changes does it?