title: Neurobiological findings in bipolar II disorder compared with findings in bipolar I disorder.
abstract: OBJECTIVE
  To determine whether there are consistent neurobiological differences between patients with bipolar I disorder (BD I) and those with bipolar II disorder (BD II).
  
  
  METHODS
  We reviewed the literature in areas where the most consistent neurobiological findings have been reported for bipolar disorder, specifically, neuroimaging and brain metabolism. The imaging studies reviewed examined structure, using magnetic resonance imaging (MRI), and function, using functional MRI, positron emission tomography, and single photon emission computed tomography. We used magnetic resonance spectroscopy to examine brain chemistry. We reviewed those metabolic studies that examined cell calcium, 3-methoxy-4-hydroxyphenylglycol, and protein kinase C.
  
  
  RESULTS
  Some genetic studies suggest that there may be differences between BD II and BD I patients. However, our review of the imaging and metabolic studies identified few studies directly comparing these 2 groups. In those studies, there were few differences, if any, and these were not consistent.
  
  
  CONCLUSIONS
  While genetic data suggest there may be differences between BD II patients and BD I patients, the neurobiological findings to date do not provide support. However, this may be owing to the small number of studies directly comparing the 2 groups and also to the fact that those carried out have not been adequately powered to detect possible small true differences. This is an important issue because, if there are no neurobiological differences, it would be anticipated that similar treatments would be similarly effective in both groups. Given the importance of understanding whether there are neurochemical differences between these groups, further research in this area is clearly needed.
authors.affiliation: Department of Psychiatry, University of Alberta, Edmonton.
authors.forename: Brent M
authors.initials: BM
authors.lastname: McGrath
authors.forename: Phillip H
authors.initials: PH
authors.lastname: Wessels
authors.forename: Emily C
authors.initials: EC
authors.lastname: Bell
authors.forename: Michele
authors.initials: M
authors.lastname: Ulrich
authors.forename: Peter H
authors.initials: PH
authors.lastname: Silverstone
mesh_terms: D001714:Bipolar Disorder / Q000145:classification* / Q000175:diagnosis* / Q000378:metabolism; D001921:Brain / Q000033:anatomy & histology / Q000098:blood supply / Q000378:metabolism; D002118:Calcium / Q000097:blood; D002560:Cerebrovascular Circulation / Q000502:physiology; D003937:Diagnosis, Differential; D006801:Humans; D008279:Magnetic Resonance Imaging; D008734:Methoxyhydroxyphenylglycol / Q000097:blood / Q000652:urine; D049268:Positron-Emission Tomography; D011493:Protein Kinase C / Q000378:metabolism; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D008734:Methoxyhydroxyphenylglycol; D011493:Protein Kinase C; D002118:Calcium