de·ment 
(dĭ-mĕnt)
(dĭ-mĕnt)tr.v. de·ment·ed, de·ment·ing, de·ments
1. To cause (a person) to become mentally deranged.
2. To cause (a person) to lose intellectual capacity.
[Late Latin dēmentāre, from Latin dēmēns, dēment-, senseless : dē-, de- + mēns, mind; see men-1 in the Appendix of Indo-European roots.]