1. Causing debilitation
   "These graceful regrets are powerless, and on the whole they are very enervating";
   - debilitative, enfeebling, weakening

1. Weaken mentally or morally
   "The constant criticism enervated his confidence"
    
2. Disturb the composure of
   "The constant noise enervated the students trying to study";
   - faze, unnerve, unsettle, rattle [informal]

See also: debilitating

Type of: discomfit, discompose, disconcert, untune [rare], upset, weaken

Encyclopedia: Enervate