Psychiatry Research 121 (2003) 51–57 0165-1781/03/$ - see front matter  2003 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/S0165-1781Ž03.00137-9 Autoantibodies to serotonin in serum of patients with psychiatric disorders Klaus Schott *, Jacques-Emmanuel Schaefer , Elke Richartz , Anil Batra , a, a a a Beate Eusterschulte , Reinhild Klein , Peter Alfred Berg , Mathias Bartels , Karl Mann , b c c a d Gerhard Buchkremer a Department of Psychiatry and Psychotherapy, University of Tubingen, Osianderstr. 24, Tubingen D-72076, a ¨ ¨ Federal Republic of Germany Vinzenz von Paul Hospital, Rottweil, Federal Republic of Germany b Laboratory of Immunopathology, Department of Internal Medicine, University of Tubingen, Federal Republic of Germany c ¨ Department of Addictive Behaviour and Addiction Medicine, Central Institute of Mental Health, d Mannheim and University of Heidelberg, Heidelberg, Federal Republic of Germany Received 11 March 2002; received in revised form 3 April 2003; accepted 16 May 2003 Abstract Antibodies to serotonin in serum were investigated by ELISA in patients with paranoid schizophrenia (Ns27), schizoaffective psychosis (Ns38), depression (Ns67), Alzheimer’s disease (Ns21), chronic alcoholism (Ns43), rheumatoid arthritis (Ns25), and multiple sclerosis (Ns16), and in healthy volunteers (Ns60). Increased antibody reactivity to serotonin was found in schizoaffective psychosis, chronic alcoholism, and rheumatoid arthritis. Decreased antibody reactivity to serotonin was found in multiple sclerosis and depression. These anti-serotonin antibodies belong to the class of so-called natural autoantibodies. Alterations of these natural autoantibodies could indicate a disturbance to the immune system. It is possible that these antibodies could also influence receptor function. Autoantibodies to neurotransmitters in a wide spectrum of psychiatric disorders have not previously been reported.  2003 Elsevier Ireland Ltd. All rights reserved. Keywords: Autoantibodies; Autoimmunity; Depression; Immunology; Neurotransmitter; Schizophrenia; Serotonin 1. Introduction Autoantibodies to serotonin in serum were first detected in fibromyalgia (Klein et al., 1992) and appear to be characteristic for this disease. Fibro- myalgia frequently coincides with psychiatric dis- *Corresponding author. Tel.: q49-7071-2986532; fax: q 49-7071-294141. E-mail address: klaus.schott@med.uni-tuebingen.de (K. Schott). orders as, for instance, depression, anxiety and somatoform disorders (Goldenberg et al., 1986; Hudson, 1992; McBeth and Silman, 2001), which are thought to represent at least partially dysregu- lations of the serotonergic neurotransmitter system in the central nervous system (CNS)(Glaser et al., 1991; Belous et al., 2001; Dursun et al., 2001). Initial studies found anti-serotonin autoantibodies in depression and paranoid schizophrenia (Schott et al., 1992); however, the results could not be