Progressive changes in glutamate concentration in early stages of schizophrenia: A longitudinal 7-Tesla MRS study

Abstract

AbstractProgressive reduction in glutamatergic transmission has been proposed as an important component of the illness trajectory of schizophrenia. Despite its popularity, to date, this notion has not been convincingly tested in patients in early stages schizophrenia. In a longitudinal 7T magnetic resonance spectroscopy (1H-MRS), we quantified glutamate at the dorsal anterior cingulate cortex in 21 participants with a median lifetime antipsychotic exposure of less than 3 days and followed them up after 6 months of treatment. Healthy controls were also scanned at two time points. While patients had significantly lower overall glutamate levels than healthy controls (F(1,27) = 5.23, p = 0.03), we did not observe a progressive change of glutamate concentration in patients (F(1,18) = 0.47, p = 0.50), and the group by time interaction was not significant (F(1,27) = 0.86, p = 0.36). On average, patients with early psychosis receiving treatment showed a 0.02 mM/year increase, while healthy controls showed a 0.06 mM/year reduction of MRS glutamate levels. Bayesian analysis of our observations does not support early, post-onset glutamate loss in schizophrenia. Interestingly, it provides evidence in favour of a lack of progressive glutamate change in our schizophrenia sample – indicating that the glutamatergic level at the onset of illness was the best predictor of the levels 6 months after treatment. A more nuanced view of glutamatergic physiology, linked to early cortical maturation, may be required to understand glutamatergic dynamics in schizophrenia.