Journal of Affective Disorders 54 (1999) 217–224 Brief report Unipolar–bipolar dichotomy of mood disorders is supported by noradrenergic brainstem system morphology * Bruno Baumann , Peter Danos, Dieter Krell, Silvia Diekmann, Cornelius Wurthmann, Hendrik Bielau, Hans-Gert Bernstein, Bernhard Bogerts Department of Psychiatry, University of Magdeburg, Leipziger Strasse 44, D-39120 Magdeburg, Germany Received 22 June 1998; received in revised form 30 August 1998; accepted 2 October 1998 Abstract Background: The biological basis of unipolar-bipolar dichotomy of mood disorders was investigated in this postmortem study by morphological comparison of the locus coeruleus (LC) as the main source of noradrenergic transmission in the brain. Methods: Numbers and the rostro-caudal as well as ventro-dorsal distribution of neuromelanin-containing neurones in the LC were determined in brainstem of 12 patients with bipolar disorder ( n 5 6) or major depression ( n 5 6), and 12 normal comparison subjects. Results: Bipolar patients had significantly more neurones on both sides of the LC as a whole than patients with major depression. Topographical analysis revealed that this difference was restricted to the rostral two thirds and the dorsal part of the LC, in which bipolar patients showed at least a trend to higher neurone numbers as compared to unipolar patients or to controls. Limitations: Small case numbers. Conclusions: Results suggest differences of innervation arising from the LC of bipolar patients as compared to patients with major depression. These first data of brainstem transmitter system morphology in unipolar and bipolar disorder are in line with neuroanatomical studies of other brain regions indicating a biological basis of the unipolar-bipolar dichotomy of mood disorders.  1999 Elsevier Science B.V. All rights reserved. Keywords: Bipolar disorder; Major depression; Classification; Locus coeruleus; Brainstem transmitter systems 1. Introduction Preisig, 1995; Weissman et al., 1996) and biological literature (Bertelsen et al., 1977; McGuffin and Katz, After the dichotomy of unipolar and bipolar forms 1989; Mendlewicz et al., 1993; Berrettini, 1995; of affective illness was proposed by Leonhard Petty, 1994; Lenox and Watson, 1994; Potter and (1979), a wide range of clinical (Winokur et al., Ketter, 1993; Hopkins and Gelenberg, 1994) focused 1969; Goodwin and Jamison, 1990; Angst and on differences between the two disorders. In the last decade some research tried to support the concept of * this classification by brain morphology derived from Corresponding author. Tel.: 1 49-391-6715029; fax: 1 49- 391-6715223. neuroimaging data. Reports of brain structural 0165-0327 / 99 / $ – see front matter  1999 Elsevier Science B.V. All rights reserved. PII: S0165-0327(98)00168-2