Citalopram or celexa (citalopram) Increases serotonin levels in the brain which has been show to decrease depression and perhaps prevent anxiety.
Most likely. If you were prescribed citalopram, I assume the doctor diagnosed major depression and/or an anxiety disorder. If so, the medicine is quite likely to improve your symptoms. However, not all low moods are major depression, and not all anxiety requires medical treatment, so if citalopram was not prescribed following a careful evaluation, the chance it will help is much less.
Maybe. Citalopram is an effective antidepressant, but it is not a great anti anxiety medication. Medications like zoloft, Cymbalta or Pristiq (desvenlafaxine) may be better choices to deal with both.