Creatine abnormalities in schizophrenia and bipolar disorder.

Total creatine (Cr) levels are widely used as an internal reference for the quantification of other metabolites in (1)H magnetic resonance spectroscopy (MRS). However, Cr plays an important role in brain energy metabolism, and its levels can be modulated by conditions of energy production and demand. Therefore, abnormal Cr levels in patient vs. control populations could confound the utility of this metabolite as an internal reference. We quantified Cr levels in 22 healthy controls, 15 acutely manic patients with bipolar disorder and 15 acutely ill patients with schizophrenia using (1)H MRS in the anterior cingulate cortex, and the parieto-occipital cortex at 4 Tesla. Patients with schizophrenia had a statistically significant reduction in Cr levels as compared with controls; bipolar disorder patients showed no difference in Cr as compared with controls. In addition, older age was associated with reductions in Cr in healthy controls, but not in patients with either disorder. These findings indicate that the use of Cr as an internal reference in schizophrenia MRS research is problematic unless Cr levels are shown to be normal in the study population. They also add to the literature on bioenergetic abnormalities in schizophrenia.