Today, scientists have found that some types of schizophrenia, which include hearing voices or having visions, may be caused by low copper levels in the body. Please get the person a full check on metal content in their system. One man commenting under the youtube video below says that he managed to cure his brother's schizophrenia:
For deflecting others' negativity which may affect the mental state of someone, it is good to recite 10:81-2; 79:28 and 7:118-22. This is from Tibb A'imma, pps 149-150.