There are several studies which have suggested some link between both high and low levels of vitamin D and schizophrenia, although definitive studies are unavailable...
Certainly, if there is a vitamin D deficiency it should be corrected, and your family physician or endocrinologist would be able to determine if intervention is needed.
For more information, see:
Arch Gen Psychiatry. 2010 Sep;67(9):889-94. Neonatal vitamin D status and risk of schizophrenia: a population-based case-control study
Bryan L. Roth, M.D., Ph.D.
Scientific Council Member
Michael Hooker Distinguished Professor
Director, NIMH Psychoactive Drug Screening Program
University of North Carolina Chapel Hill Medical School