1. ¹Menninger Department of Psychiatry and Behavioral Sciences, Baylor College of Medicine, Houston, TX, USA
2. ²Institute of Mental Health, Peking University, Beijing, PR China
3. ³Center for Biological Psychiatry, Beijing HuiLongGuan Hospital, Beijing, PR China

Correspondence: Dr XY Zhang, Menninger Department of Psychiatry and Behavioral Sciences, Baylor College of Medicine, VA Medical Center, Research Building 109, Room 130, 2002 Holcombe Boulevard, Houston, TX 77030, USA. Tel: +1 713 791 1414 ext. 5824; Fax: +1 713 794 7938; E-mail: xyzhang@bcm.edu; Dr DF Zhou, Institute of Mental Health, Peking University, 51 Hua-Yuan-Bei Road, Hai-Dian District, Beijing 100083, PR China. Tel: +86 10 82801998; Fax: +86 10 62027314; E-mail: zhoudf@bjmu.edu.cn

⁴These two authors contributed equally to the study.

Received 30 May 2006; Revised 29 October 2006; Accepted 27 November 2006; Published online 17 January 2007.

Abstract

The high rate of smoking in schizophrenia may reflect patients' attempts to reduce the side effects of antipsychotic medications, and one mechanism for this reduction may be a reduction in oxidative stress and free radical-mediated brain damage that may contribute to schizophrenic symptoms and to complications of its treatment. Symptoms were assessed with the Positive and Negative Syndrome Scale (PANSS), side effects were assessed with the Simpson and Angus Rating Scale (SAS), and malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) activities were measured in plasma. All of these measures were compared in 130 male inpatients with DSM-IV schizophrenia: 104 smokers and 26 non-smokers. The results showed that the positive PANSS symptoms were lower in smokers than non-smokers (14.5 vs 17.5), while the negative symptoms were lower in those who smoked more cigarettes (r=-0.23). The SAS showed no differences. The CAT activity was correlated with both GSH-Px and SOD activities. Of the three enzymes only the CAT activity was significantly higher in smokers than non-smokers (2.9 vs 1.6 U/ml), but greater SOD activity correlated more cigarettes smoked (r=0.24). Consistent with some protection against oxidative stress, MDA also was significantly lower in smokers than non-smokers (9.2 vs 14.4 nmol/ml). The fewer positive symptoms in smokers and fewer negative symptoms in those who smoked more cigarettes may be a selection bias, but appears to be associated with decreased oxidative stress and lipid peroxidation in schizophrenics who smoke tobacco.