title: Treatment-Resistant Schizophrenia Patients Show Elevated Anterior Cingulate Cortex Glutamate Compared to Treatment-Responsive.
abstract: BACKGROUND
  Resistance to antipsychotic treatment is a significant clinical problem in patients with schizophrenia with approximately 1 in 3 showing limited or no response to repeated treatments with antipsychotic medication. The neurobiological basis for treatment resistance is unknown but recent evidence implicates glutamatergic function in the anterior cingulate cortex. We examined glutamate levels of chronically ill treatment-resistant patients directly compared to treatment-responsive patients.
  
  
  METHODS
  We acquired proton magnetic resonance spectroscopy (1H-MRS) at 3 Tesla from 21 treatment-resistant and 20 treatment-responsive patients. All participants had a DSM-IV diagnosis of schizophrenia. Treatment-resistant patients were classified using the modified Kane criteria. The groups were matched for age, sex, smoking status, and illness duration.
  
  
  RESULTS
  Glutamate to creatine ratio levels were higher in treatment-resistant patients (Mean [SD] = 1.57 [0.24]) than in treatment-responsive patients (Mean[SD] = 1.38 [0.23]), (T[35] = 2.34, P = .025, 2-tailed), with a large effect size of d = 0.76. A model assuming 2 populations showed a 25% improvement in the fit of the Akaike weights (0.55) over a model assuming 1 population (0.44), producing group values almost identical to actual group means.
  
  
  CONCLUSIONS
  Increased anterior cingulate glutamate level is associated with treatment-resistant schizophrenia. This appears to be a stable neurobiological trait of treatment-resistant patients. We discuss possible explanations for glutamatergic dysfunction playing a significant role in resistance to conventional antipsychotic treatments, which are all dopamine-2 receptor blockers. Our findings suggest that glutamatergic treatments may be particularly effective in resistant patients and that 1H-MRS glutamate indices can potentially have clinical use.
authors.affiliation: Medical Research Council Clinical Sciences Centre, Psychiatric Imaging Group, Hammersmith Hospital, London, UK; Institute of Psychiatry Psychology and Neuroscience, Department of Psychosis Studies, King's College London, UK; elias.mouchlianitis@kcl.ac.uk.
authors.forename: Elias
authors.initials: E
authors.lastname: Mouchlianitis
authors.affiliation: Medical Research Council Clinical Sciences Centre, Psychiatric Imaging Group, Hammersmith Hospital, London, UK; University College London, Division of Psychiatry, London, UK;
authors.forename: Michael A P
authors.initials: MA
authors.lastname: Bloomfield
authors.affiliation: Medical Research Council Clinical Sciences Centre, Psychiatric Imaging Group, Hammersmith Hospital, London, UK;
authors.forename: Vincent
authors.initials: V
authors.lastname: Law
authors.affiliation: Institute of Psychiatry Psychology and Neuroscience, Department of Psychosis Studies, King's College London, UK;
authors.forename: Katherine
authors.initials: K
authors.lastname: Beck
authors.affiliation: Department of Psychiatry and Behavioral Sciences, University of Texas, Houston, TX;
authors.forename: Sudhakar
authors.initials: S
authors.lastname: Selvaraj
authors.affiliation: Partnerships in Care, Mental Health Division, London, UK;
authors.forename: Naresh
authors.initials: N
authors.lastname: Rasquinha
authors.affiliation: Division of Brain Sciences, Imperial College London, Hammersmith Hospital, London, UK.
authors.forename: Adam
authors.initials: A
authors.lastname: Waldman
authors.affiliation: Institute of Psychiatry Psychology and Neuroscience, Department of Psychosis Studies, King's College London, UK;
authors.forename: Federico E
authors.initials: FE
authors.lastname: Turkheimer
authors.affiliation: Institute of Psychiatry Psychology and Neuroscience, Department of Psychosis Studies, King's College London, UK;
authors.forename: Alice
authors.initials: A
authors.lastname: Egerton
authors.affiliation: Medical Research Council Clinical Sciences Centre, Psychiatric Imaging Group, Hammersmith Hospital, London, UK; Institute of Psychiatry Psychology and Neuroscience, Department of Psychosis Studies, King's College London, UK;
authors.forename: James
authors.initials: J
authors.lastname: Stone
authors.affiliation: Medical Research Council Clinical Sciences Centre, Psychiatric Imaging Group, Hammersmith Hospital, London, UK; Institute of Psychiatry Psychology and Neuroscience, Department of Psychosis Studies, King's College London, UK;
authors.forename: Oliver D
authors.initials: OD
authors.lastname: Howes
mesh_terms: D000328:Adult; D014150:Antipsychotic Agents / Q000494:pharmacology*; D002908:Chronic Disease; D004351:Drug Resistance; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism*; D006179:Gyrus Cinguli / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D012559:Schizophrenia / Q000188:drug therapy* / Q000378:metabolism*
chemical_list: D014150:Antipsychotic Agents; D018698:Glutamic Acid
keywords: 1H-MRS; NMDA; antipsychotics; glutamate; imaging and schizophrenia; neurochemistry; psychosis; treatment- resistance