title: Cigarette smoking is associated with thinner cingulate and insular cortices in patients with severe mental illness.
abstract: BACKGROUND
  Magnetic resonance imaging (MRI) studies show reduced cortical thickness in patients with schizophrenia and bipolar disorder. These subtle brain abnormalities may provide insight into illness mechanisms. However, environmental and lifestyle-related factors, such as cigarette smoking, may contribute to brain structure changes. Cigarette smoking is highly prevalent in patients with severe mental illness. In nonpsychiatric samples, smoking has been associated with reduced thickness in the anterior (ACC) and posterior cingulate cortices, the insular cortex (INS), the dorsolateral prefrontal cortex and the orbitofrontal cortex.
  
  
  METHODS
  We examined MRI scans from patients with schizophrenia, other psychotic disorders or bipolar disorder and healthy controls using FreeSurfer.
  
  
  RESULTS
  We included 506 patients (49% smokers) and 237 controls (20% smokers) in our study. We found reduced cortical thickness in the left rostral ACC and the left INS in smoking patients compared with nonsmoking patients, but this difference was not found among healthy controls. No dose-response relationship was found between amount of smoking and cortical thickness in these regions. Among patients, maps of thickness along the whole cortical surface revealed reduced insular thickness but no effects in other regions. Among healthy controls, similar analyses revealed increased age-related cortical thinning in the left occipital lobe among smokers compared with nonsmokers.
  
  
  CONCLUSIONS
  The causal direction could not be determined owing to the cross-sectional design and lack of detailed data on smoking addiction and smoking history.
  
  
  CONCLUSIONS
  The effect of cigarette smoking should be considered in MRI studies of patients with severe mental illness.
authors: Department of Psychiatric Research, Diakonhjemmet Hospital; and NORMENT and K.G. Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
authors: Kjetil Nordbø
authors: KN
authors: Jørgensen
authors: Department of Psychiatric Research, Diakonhjemmet Hospital; and the Norwegian Centre for Addiction Research (SERAF), Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
authors: Ingeborg
authors: I
authors: Skjærvø
authors: Department of Psychiatric Research, Diakonhjemmet Hospital; and NORMENT and K.G. Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
authors: Lynn
authors: L
authors: Mørch-Johnsen
authors: Department of Psychiatric Research, Diakonhjemmet Hospital; and NORMENT and K.G. Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
authors: Unn Kristin
authors: UK
authors: Haukvik
authors: Department of Psychiatric Research, Diakonhjemmet Hospital; and NORMENT and K.G. Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
authors: Elisabeth Heffermehl
authors: EH
authors: Lange
authors: NORMENT and K.G. Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo; and the Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway.
authors: Ingrid
authors: I
authors: Melle
authors: NORMENT and K.G. Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo; and the Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway.
authors: Ole Andreas
authors: OA
authors: Andreassen
authors: Department of Psychiatric Research, Diakonhjemmet Hospital; and NORMENT and K.G. Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
authors: Ingrid
authors: I
authors: Agartz
mesh_terms: D000328:Adult; D000375:Aging / Q000473:pathology; D001714:Bipolar Disorder / Q000150:complications / Q000473:pathology*; D002540:Cerebral Cortex / Q000473:pathology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009929:Organ Size; D011569:Psychiatric Status Rating Scales; D011618:Psychotic Disorders / Q000150:complications / Q000473:pathology*; D012559:Schizophrenia / Q000150:complications / Q000473:pathology*; D012720:Severity of Illness Index; D012907:Smoking / Q000473:pathology*; D014029:Tobacco Use Disorder / Q000150:complications / Q000473:pathology*