Manifestations? I dont know if it really manifests itself with psychological abnormalities. Most manifestations would be behavioral I would say. Learned conditioning (often unconscious) for how to avoid stuttering. These behaviors in time can become ingrained into a stutterer's speaking pattern. The other manifested conditions would probably be emotional as opposed to psychological. The disfluency that people see is just a small part of what stutterers deal with. Just the surface stuff. Below is all the shame/guilty/embarrassment/fear/anxiety/denial/etc...