38 CFR 4.127: Intellectual disability (intellectual developmental disorder) and personality disorders.

Intellectual disability (intellectual developmental disorder) and personality disorders are not diseases or injuries for compensation purposes, and, except as provided in § 3.310(a) of this chapter, disability resulting from them may not be service-connected. However, disability resulting from a mental disorder that is superimposed upon intellectual disability (intellectual developmental disorder) or a personality disorder may be service-connected.