Dear Narelle
I am not aware of any studies stating that Effexor worsens the symptoms of spasmodic dysphonia. Neurologically, effexor can some times cause amnesia, confusion, twitching, increase the involuntary movements. Since you are already experiencing increased anxiety from Effexor, I would recommend that you talk to your doctor about your concerns
Yours Sincerely
HFHS-M.D.