The Collaborative International Dictionary of English v.0.48:

Overanxious \O"ver*anx"ious\, a.
   Anxious in an excessive or needless degree. --
   O"ver*anx"ious*ly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

overanxious
    adj 1: anxious or nervous to an excessive degree

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "overanxious":
   agitated, all-overish, anxious, anxioused up, apprehensive,
   at fever pitch, bothered, concerned, delirious, disquieted,
   disturbed, fanatical, fearful, febrile, feverish, foreboding,
   frantic, frenetic, frenzied, furious, hectic, hysteric,
   in a pucker, in a stew, infatuated, insane, misgiving, nervous,
   on tenterhooks, overapprehensive, overdesirous, overeager,
   overenthusiastic, overzealous, perfervid, perturbed, solicitous,
   strained, suspenseful, tense, troubled, ultrazealous, uneasy, wild,
   zealous