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Current cigarette smoking in Chinese female patients with schizophrenia: A meta-analysis
Psychiatry Research 235 (2016) 203–205
Contents lists available at ScienceDirect
Psychiatry Research journal homepage: www.elsevier.com/locate/psychres
Short communication
Current cigarette smoking in Chinese female patients with schizophrenia: A meta-analysis Xiao-Lan Cao a,b,1, Yan Li a,1, Bao-Liang Zhong a,1, Helen F.K. Chiu a, Gabor S. Ungvari c,d, Chee H. Ng e, Yu-Tao Xiang f,n a
Department of Psychiatry, Chinese University of Hong Kong, Hong Kong SAR, China Shenzhen Key Laboratory for Psychological Healthcare & Shenzhen Institute of Mental Health, Shenzhen Kangning Hospital & Shenzhen Mental Health Center, Shenzhen, China c School of Psychiatry and Clinical Neurosciences, University of Western Australia, Perth, Australia d The University of Notre Dame Australia/Marian Centre, Perth, Australia e Department of Psychiatry, University of Melbourne, Melbourne, Victoria, Australia f Unit of Psychiatry, Faculty of Health Sciences, University of Macau, Macao SAR, China b
art ic l e i nf o
a b s t r a c t
Article history: Received 6 August 2015 Received in revised form 24 October 2015 Accepted 27 November 2015 Available online 3 December 2015
The study objective was to perform a meta-analysis of the prevalence of current smoking in Chinese female patients with schizophrenia. A systematic literature search was conducted and studies fulfilling the following criteria were included: female schizophrenia patients; reporting current smoking rate computed from samples. Eight studies were included. The pooled current smoking prevalence was 4.3% (95% Confidence interval [CI]: 3.2–5.6%). The finding showed that smoking rate of female patients with schizophrenia in China was lower compared to their Western and other Asian counterparts. & 2015 Elsevier Ireland Ltd. All rights reserved.
Keywords: Smoke Schizophrenia China
1. Introduction Smoking is one of the major preventable causes of morbidity and premature mortality both in the general population and in schizophrenia (Kelly et al., 2011). In the past decades numerous studies examined smoking in schizophrenia patients in Western countries. In recent years, a number of surveys examining smoking rate in schizophrenia have been conducted in China, but most focused on male patients (Chen et al., 1999; Liu et al., 2011) and female patients were often not involved (Tang et al., 2007a). This is a systematic review and meta-analysis to determine the rate of smoking in female schizophrenia patients in China.
2. Methods A systematic search was performed for relevant studies in PubMed, Medline, EMBASE, China Journal Net (CJN), WanFang Data, SinoMed and Taiwan Electronic Periodical Services databases from their inception until June 20, 2015. Search items used were as n Correspondence to: 3/F, Building E12, Faculty of Health Sciences, University of Macau, Avenida da Universidade, Taipa, Macau SAR 999078, China. E-mail address: [email protected] (Y.-T. Xiang). 1 These authors contributed equally to the paper.
http://dx.doi.org/10.1016/j.psychres.2015.11.050 0165-1781/& 2015 Elsevier Ireland Ltd. All rights reserved.
follows: (“smoking” or “tobacco” or “cigarette” or “nicotine”) and “schizophrenia” and (“China” or “Chinese”). The inclusion criteria were: (a) female schizophrenia patients in China (b) and reporting current smoking rate computed from the study samples. Studies with potentially biased samples, such as pharmacological trials, or smoking treatment interventions were excluded. The 22-item Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) was used to assess the quality of papers (von Elm et al., 2007). Studies with a score of 11 or less were classified as ‘poor quality’ (Cao et al., 2015). The pooled prevalence was calculated using a fixed or random effect model. The I2 statistic was used to assess heterogeneity. When I2 statistic was less than 50%, the fixed effect model was preferred as the pooling method (Higgins et al., 2003); otherwise random effect model was conducted. All statistical analyses were conducted using the Comprehensive Meta Analysis software, Version 2 (Biosta, Inc., USA).
3. Results The literature search identified 724 potential articles of which eight studies (Chen et al., 2009; Du, 2007; Hou et al., 2011; Li, 2006; Tang et al., 2014, 2007b; Zhang et al., 2012, 2010) were included (Table 1). The quality score of studies ranged between 14
204
X.-L. Cao et al. / Psychiatry Research 235 (2016) 203–205
Table 1 Summary of the studies included in the meta-analysis. Author
Publication year City
Source of patients
Age (years) Duration of illness (years)
Sample size Number of current smokers
Prevalence of current smoker (%)
Li, C.X. Du, L. Tang, Y.L. Chen, D.C. Zhang, X.Y. Hou, Y.Z. Zhang, X.Y.
2006 2007 2007 2009 2010 2011 2012
Mixeda Mixeda Inpatients Inpatients Inpatients Community Inpatients
NR NR 44.5 NR NR NR 40.4
NR NR 15.9 NR NR NR NR
90 79 244 42 63 273 288
2 4 11 3 5 11 10
2.2 5.1 4.5 7.1 7.9 4.0 3.5
Tang, W.
2014
Inpatients
NR
NR
105
2
1.9
Chendu Chongqing Beijing Beijing Beijing Beijing Beijing and Baoding Wenzhou
NR: Not Reported. a
Outpatients and inpatients.
Fig. 1. The rate of current smoking in Chinese female schizophrenia patients.
and 20 according to the STROBE. Common problems were inadequate description of the sample size estimation (8 reports) and sampling method (5 reports). The 8 studies were considerably homogeneous (I2 ¼ 0, P ¼0.57; Fig. 1). Using the fixed effect model, the pooled current smoking prevalence in the pooled sample of 1184 was 4.3% (95% Confidence interval [CI], 3.2–5.6%).
4. Discussion To the best of our our knowledge, this was the first metaanalysis to examine the rate of current smoking in female schizophrenia patients in China. In a large-scale survey on smoking in Chinese general population (Zhang et al., 2014), the prevalence of smoking in women was 3.4%, slightly lower than our result in female schizophrenia patients (4.3%). Possible reasons for the higher smoking rate in schizophrenia compared to the general population have been attributed to both environmental and biological factors, for instance, schizophrenia patients are often unemployed, thus smoke as a behavioural filler (Roick et al., 2007). In addition, nicotine could improve psychotic symptoms and side effects of antipsychotics (Kumari and Postma, 2005). In a meta-analysis with most studies conducted in Western countries the current smoking rates in female schizophrenia patients ranged from 13 to 82%; the corresponding figure was 24% in
Japan, 10% in Singapore and 12% in Taiwan (de Leon and Diaz, 2005). In recent studies the smoking rate in female schizophrenia patients was 14.4% in Japan (Umene-Nakano et al., 2013) and 21% in Korea (Kim et al., 2013). The pooled smoking rate in Chinese female patients in our study, however, was significantly lower than the above figures. The underlying reasons for lower smoking rate in Chinese patients than the worldwide rates are unclear. We hypothesise that it could probably be due to the ‘floor effect’; i.e., even if the association between schizophrenia and smoking is well established by biological mechanisms (de Leon and Diaz, 2005), restricted access to tobacco and/or strong cultural and social pressure and factors against women's smoking may strongly bias the association (Jackson et al., 2015). Such ‘floor effect’ often occurs in some non-Western countries where female smoking is relatively rare (Jackson et al., 2015). In the Chinese general population, females are much less likely to smoke than males, with the ratio being around 0.13 (female/male: 4.8% vs. 37.6%) (Ma et al., 2009). In a study reporting smoking rate in both genders, the female/male schizophrenia patient ratio was 0.07 (4.0% vs. 53.6%) (Hou et al., 2011), also indicating the ‘floor effect’ on smoking rate in female patients. Finally, public health education and economic factors may also influence the rates of smoking in schizophrenia. The meta-analysis has several limitations. Only eight studies were included, which hinders more sophisticated analyses such as meta-regression analysis. In addition, publication bias was not assessed as a minimum of 10 studies would have been required for that purpose.
X.-L. Cao et al. / Psychiatry Research 235 (2016) 203–205
In conclusion, smoking rate in female schizophrenia patients in China is lower than those reported from Western and other Asian countries (de Leon and Diaz, 2005). Socio-cultural factors accounting for the low smoking rate warrants further examination in future studies.
Conflict of interests The authors had no conflicts of interest in conducting this study or preparing the manuscript.
Acknowledgements The study was supported by the Start-up Research Grant (SRG2014-00019-FHS) and Multi-Year Research Grant (MYRG201500230-FHS) from University of Macau.
Appendix A. Supplementary material Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.psychres.2015.11. 050.
References Cao, X.L., Zhong, B.L., Xiang, Y.T., Ungvari, G.S., Lai, K.Y., Chiu, H.F., Caine, E.D., 2015. Prevalence of suicidal ideation and suicide attempts in the general population of China: a meta-analysis. Int. J. Psychiatry Med. 49, 296–308. Chen, D.C., Zhang, X.Y., Li, Y.L., Wang, N., Nie, Y., Yang, K.B., Tang, Y.L., Zhou, D.F., 2009. Association of smoking and psychiatric symptoms, clinical characteristics and cognitive function in first-episode schizophrenia inpatients. Chin. Ment. Health J. 23, 1–4 (in Chinese). Chen, Z.E., Zhang, X.J., Lou, L., Xu, M.Y., Ma, P.D., 1999. The study of smoking in male schizophrenia patients. J. Behav. Med. Sci. 8, 147–148 (in Chinese). de Leon, J., Diaz, F.J., 2005. A meta-analysis of worldwide studies demonstrates an association between schizophrenia and tobacco smoking behaviors. Schizophr. Res. 76, 135–157. Du, L., 2007. Study on the Smoking Behavior of Schizophrenia and Related Molecular Genetics. Department of Psychiatry, Chongqing Medical University, Chongqing (in Chinese). Higgins, J.P., Thompson, S.G., Deeks, J.J., Altman, D.G., 2003. Measuring
205
inconsistency in meta-analyses. Br. Med. J. 327, 557–560. Hou, Y.Z., Xiang, Y.T., Yan, F., Ungvari, G.S., Dickerson, F., Chiu, H.F., Lai, K.Y., Lee, E.H., Li, W.Y., Li, W.X., Zhu, Y.L., Dixon, L.B., 2011. Cigarette smoking in communitydwelling patients with schizophrenia in China. J. Psychiatr. Res. 45, 1551–1556. Jackson, J.G., Diaz, F.J., Lopez, L., de Leon, J., 2015. A combined analysis of worldwide studies demonstrates an association between bipolar disorder and tobacco smoking behaviors in adults. Bipolar Disord. 17, 575–597. Kelly, D.L., McMahon, R.P., Wehring, H.J., Liu, F., Mackowick, K.M., Boggs, D.L., Warren, K.R., Feldman, S., Shim, J.C., Love, R.C., Dixon, L., 2011. Cigarette smoking and mortality risk in people with schizophrenia. Schizophr. Bull. 37, 832–838. Kim, S.S., Chung, S., Park, J.I., Jung, A.J., Kalman, D., Ziedonis, D.M., 2013. Smoking among individuals with schizophrenia in Korea: gender differences. Arch. Psychiatr. Nurs. 27, 241–245. Kumari, V., Postma, P., 2005. Nicotine use in schizophrenia: the self medication hypotheses. Neurosci. Biobehav. Rev. 29, 1021–1034. Li, C.X., 2006. Exploring the Relationship among Smoking Schizophrenia and Related Neurocognitive Functions and a Pilot Molecular Genetic Study. Huaxi Mental Health Centre, Sichuan University, Sichuan (in Chinese). Liu, Q., Yang, X.J., He, S.L., Li, C.L., Yang, J., 2011. The effects of smoking on male schizophrenia patients. Sichuan Ment. Health 24, 35–37 (in Chinese). Ma, X., Xiang, Y.T., Cai, Z.J., Li, S.R., Xiang, Y.Q., Guo, H.L., Hou, Y.Z., Li, Z.B., Li, Z.J., Tao, Y.F., Dang, W.M., Wu, X.M., Deng, J., Lai, K.Y., Ungvari, G.S., 2009. Smoking and psychiatric disorders in the rural and urban regions of Beijing, China: a community-based survey. Drug Alcohol Depend. 100, 146–152. Roick, C., Fritz-Wieacker, A., Matschinger, H., Heider, D., Schindler, J., Riedel-Heller, S., Angermeyer, M.C., 2007. Health habits of patients with schizophrenia. Soc. Psychiatry Psychiatr. Epidemiol. 42, 268–276. Tang, W., Wen, N., Liu, J.H., 2014. A survey on the reasons of smoking and nicotine dependence in patients with schizophrenia , Zhejiang. Prev. Med. 26, 253–256 (in Chinese). Tang, Y.L., George, T.P., Mao, P.X., Cai, Z.J., Chen, Q., 2007a. Cigarette smoking in Chinese male inpatients with schizophrenia: a cross-sectional analysis. J. Psychiatr. Res. 41, 43–48. Tang, Y.L., Gillespie, C.F., Epstein, M.P., Mao, P.X., Jiang, F., Chen, Q., Cai, Z.J., Mitchell, P.B., 2007b. Gender differences in 542 Chinese inpatients with schizophrenia. Schizophr. Res. 97, 88–96. Umene-Nakano, W., Yoshimura, R., Hoshuyama, T., Yoshii, C., Hayashi, K., Nakano, H., Hori, H., Ikenouchi-Sugita, A., Katsuki, A., Atake, K., Nakamura, J., 2013. Current smoking rate in patients with psychiatric disorders in Japan: questionnaire survey. Psychiatry Res. 210, 268–273. von Elm, E., Altman, D.G., Egger, M., Pocock, S.J., Gotzsche, P.C., Vandenbroucke, J.P., 2007. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies. PLoS Med. 4, e296. Zhang, R., Cao, Q., Lu, Y., 2014. The analysis of cigarette smoking behaviors and its influecing factors among Chinese urban and rural residents. Acta Univ. Med. Nanjing (Nat. Sci.) 34, 84–89 (in Chinese). Zhang, X.Y., Chen da, C., Xiu, M.H., Yang, F.D., Haile, C.N., Kosten, T.A., Kosten, T.R., 2012. Gender differences in never-medicated first-episode schizophrenia and medicated chronic schizophrenia patients. J. Clin. Psychiatry 73, 1025–1033. Zhang, X.Y., Xiu, M.H., Song, C., Chen da, C., Wu, G.Y., Haile, C.N., Kosten, T.A., Kosten, T.R., 2010. Increased serum S100B in never-medicated and medicated schizophrenic patients. J. Psychiatr. Res. 44, 1236–1240.
Contents lists available at ScienceDirect
Psychiatry Research journal homepage: www.elsevier.com/locate/psychres
Short communication
Current cigarette smoking in Chinese female patients with schizophrenia: A meta-analysis Xiao-Lan Cao a,b,1, Yan Li a,1, Bao-Liang Zhong a,1, Helen F.K. Chiu a, Gabor S. Ungvari c,d, Chee H. Ng e, Yu-Tao Xiang f,n a
Department of Psychiatry, Chinese University of Hong Kong, Hong Kong SAR, China Shenzhen Key Laboratory for Psychological Healthcare & Shenzhen Institute of Mental Health, Shenzhen Kangning Hospital & Shenzhen Mental Health Center, Shenzhen, China c School of Psychiatry and Clinical Neurosciences, University of Western Australia, Perth, Australia d The University of Notre Dame Australia/Marian Centre, Perth, Australia e Department of Psychiatry, University of Melbourne, Melbourne, Victoria, Australia f Unit of Psychiatry, Faculty of Health Sciences, University of Macau, Macao SAR, China b
art ic l e i nf o
a b s t r a c t
Article history: Received 6 August 2015 Received in revised form 24 October 2015 Accepted 27 November 2015 Available online 3 December 2015
The study objective was to perform a meta-analysis of the prevalence of current smoking in Chinese female patients with schizophrenia. A systematic literature search was conducted and studies fulfilling the following criteria were included: female schizophrenia patients; reporting current smoking rate computed from samples. Eight studies were included. The pooled current smoking prevalence was 4.3% (95% Confidence interval [CI]: 3.2–5.6%). The finding showed that smoking rate of female patients with schizophrenia in China was lower compared to their Western and other Asian counterparts. & 2015 Elsevier Ireland Ltd. All rights reserved.
Keywords: Smoke Schizophrenia China
1. Introduction Smoking is one of the major preventable causes of morbidity and premature mortality both in the general population and in schizophrenia (Kelly et al., 2011). In the past decades numerous studies examined smoking in schizophrenia patients in Western countries. In recent years, a number of surveys examining smoking rate in schizophrenia have been conducted in China, but most focused on male patients (Chen et al., 1999; Liu et al., 2011) and female patients were often not involved (Tang et al., 2007a). This is a systematic review and meta-analysis to determine the rate of smoking in female schizophrenia patients in China.
2. Methods A systematic search was performed for relevant studies in PubMed, Medline, EMBASE, China Journal Net (CJN), WanFang Data, SinoMed and Taiwan Electronic Periodical Services databases from their inception until June 20, 2015. Search items used were as n Correspondence to: 3/F, Building E12, Faculty of Health Sciences, University of Macau, Avenida da Universidade, Taipa, Macau SAR 999078, China. E-mail address: [email protected] (Y.-T. Xiang). 1 These authors contributed equally to the paper.
http://dx.doi.org/10.1016/j.psychres.2015.11.050 0165-1781/& 2015 Elsevier Ireland Ltd. All rights reserved.
follows: (“smoking” or “tobacco” or “cigarette” or “nicotine”) and “schizophrenia” and (“China” or “Chinese”). The inclusion criteria were: (a) female schizophrenia patients in China (b) and reporting current smoking rate computed from the study samples. Studies with potentially biased samples, such as pharmacological trials, or smoking treatment interventions were excluded. The 22-item Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) was used to assess the quality of papers (von Elm et al., 2007). Studies with a score of 11 or less were classified as ‘poor quality’ (Cao et al., 2015). The pooled prevalence was calculated using a fixed or random effect model. The I2 statistic was used to assess heterogeneity. When I2 statistic was less than 50%, the fixed effect model was preferred as the pooling method (Higgins et al., 2003); otherwise random effect model was conducted. All statistical analyses were conducted using the Comprehensive Meta Analysis software, Version 2 (Biosta, Inc., USA).
3. Results The literature search identified 724 potential articles of which eight studies (Chen et al., 2009; Du, 2007; Hou et al., 2011; Li, 2006; Tang et al., 2014, 2007b; Zhang et al., 2012, 2010) were included (Table 1). The quality score of studies ranged between 14
204
X.-L. Cao et al. / Psychiatry Research 235 (2016) 203–205
Table 1 Summary of the studies included in the meta-analysis. Author
Publication year City
Source of patients
Age (years) Duration of illness (years)
Sample size Number of current smokers
Prevalence of current smoker (%)
Li, C.X. Du, L. Tang, Y.L. Chen, D.C. Zhang, X.Y. Hou, Y.Z. Zhang, X.Y.
2006 2007 2007 2009 2010 2011 2012
Mixeda Mixeda Inpatients Inpatients Inpatients Community Inpatients
NR NR 44.5 NR NR NR 40.4
NR NR 15.9 NR NR NR NR
90 79 244 42 63 273 288
2 4 11 3 5 11 10
2.2 5.1 4.5 7.1 7.9 4.0 3.5
Tang, W.
2014
Inpatients
NR
NR
105
2
1.9
Chendu Chongqing Beijing Beijing Beijing Beijing Beijing and Baoding Wenzhou
NR: Not Reported. a
Outpatients and inpatients.
Fig. 1. The rate of current smoking in Chinese female schizophrenia patients.
and 20 according to the STROBE. Common problems were inadequate description of the sample size estimation (8 reports) and sampling method (5 reports). The 8 studies were considerably homogeneous (I2 ¼ 0, P ¼0.57; Fig. 1). Using the fixed effect model, the pooled current smoking prevalence in the pooled sample of 1184 was 4.3% (95% Confidence interval [CI], 3.2–5.6%).
4. Discussion To the best of our our knowledge, this was the first metaanalysis to examine the rate of current smoking in female schizophrenia patients in China. In a large-scale survey on smoking in Chinese general population (Zhang et al., 2014), the prevalence of smoking in women was 3.4%, slightly lower than our result in female schizophrenia patients (4.3%). Possible reasons for the higher smoking rate in schizophrenia compared to the general population have been attributed to both environmental and biological factors, for instance, schizophrenia patients are often unemployed, thus smoke as a behavioural filler (Roick et al., 2007). In addition, nicotine could improve psychotic symptoms and side effects of antipsychotics (Kumari and Postma, 2005). In a meta-analysis with most studies conducted in Western countries the current smoking rates in female schizophrenia patients ranged from 13 to 82%; the corresponding figure was 24% in
Japan, 10% in Singapore and 12% in Taiwan (de Leon and Diaz, 2005). In recent studies the smoking rate in female schizophrenia patients was 14.4% in Japan (Umene-Nakano et al., 2013) and 21% in Korea (Kim et al., 2013). The pooled smoking rate in Chinese female patients in our study, however, was significantly lower than the above figures. The underlying reasons for lower smoking rate in Chinese patients than the worldwide rates are unclear. We hypothesise that it could probably be due to the ‘floor effect’; i.e., even if the association between schizophrenia and smoking is well established by biological mechanisms (de Leon and Diaz, 2005), restricted access to tobacco and/or strong cultural and social pressure and factors against women's smoking may strongly bias the association (Jackson et al., 2015). Such ‘floor effect’ often occurs in some non-Western countries where female smoking is relatively rare (Jackson et al., 2015). In the Chinese general population, females are much less likely to smoke than males, with the ratio being around 0.13 (female/male: 4.8% vs. 37.6%) (Ma et al., 2009). In a study reporting smoking rate in both genders, the female/male schizophrenia patient ratio was 0.07 (4.0% vs. 53.6%) (Hou et al., 2011), also indicating the ‘floor effect’ on smoking rate in female patients. Finally, public health education and economic factors may also influence the rates of smoking in schizophrenia. The meta-analysis has several limitations. Only eight studies were included, which hinders more sophisticated analyses such as meta-regression analysis. In addition, publication bias was not assessed as a minimum of 10 studies would have been required for that purpose.
X.-L. Cao et al. / Psychiatry Research 235 (2016) 203–205
In conclusion, smoking rate in female schizophrenia patients in China is lower than those reported from Western and other Asian countries (de Leon and Diaz, 2005). Socio-cultural factors accounting for the low smoking rate warrants further examination in future studies.
Conflict of interests The authors had no conflicts of interest in conducting this study or preparing the manuscript.
Acknowledgements The study was supported by the Start-up Research Grant (SRG2014-00019-FHS) and Multi-Year Research Grant (MYRG201500230-FHS) from University of Macau.
Appendix A. Supplementary material Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.psychres.2015.11. 050.
References Cao, X.L., Zhong, B.L., Xiang, Y.T., Ungvari, G.S., Lai, K.Y., Chiu, H.F., Caine, E.D., 2015. Prevalence of suicidal ideation and suicide attempts in the general population of China: a meta-analysis. Int. J. Psychiatry Med. 49, 296–308. Chen, D.C., Zhang, X.Y., Li, Y.L., Wang, N., Nie, Y., Yang, K.B., Tang, Y.L., Zhou, D.F., 2009. Association of smoking and psychiatric symptoms, clinical characteristics and cognitive function in first-episode schizophrenia inpatients. Chin. Ment. Health J. 23, 1–4 (in Chinese). Chen, Z.E., Zhang, X.J., Lou, L., Xu, M.Y., Ma, P.D., 1999. The study of smoking in male schizophrenia patients. J. Behav. Med. Sci. 8, 147–148 (in Chinese). de Leon, J., Diaz, F.J., 2005. A meta-analysis of worldwide studies demonstrates an association between schizophrenia and tobacco smoking behaviors. Schizophr. Res. 76, 135–157. Du, L., 2007. Study on the Smoking Behavior of Schizophrenia and Related Molecular Genetics. Department of Psychiatry, Chongqing Medical University, Chongqing (in Chinese). Higgins, J.P., Thompson, S.G., Deeks, J.J., Altman, D.G., 2003. Measuring
205
inconsistency in meta-analyses. Br. Med. J. 327, 557–560. Hou, Y.Z., Xiang, Y.T., Yan, F., Ungvari, G.S., Dickerson, F., Chiu, H.F., Lai, K.Y., Lee, E.H., Li, W.Y., Li, W.X., Zhu, Y.L., Dixon, L.B., 2011. Cigarette smoking in communitydwelling patients with schizophrenia in China. J. Psychiatr. Res. 45, 1551–1556. Jackson, J.G., Diaz, F.J., Lopez, L., de Leon, J., 2015. A combined analysis of worldwide studies demonstrates an association between bipolar disorder and tobacco smoking behaviors in adults. Bipolar Disord. 17, 575–597. Kelly, D.L., McMahon, R.P., Wehring, H.J., Liu, F., Mackowick, K.M., Boggs, D.L., Warren, K.R., Feldman, S., Shim, J.C., Love, R.C., Dixon, L., 2011. Cigarette smoking and mortality risk in people with schizophrenia. Schizophr. Bull. 37, 832–838. Kim, S.S., Chung, S., Park, J.I., Jung, A.J., Kalman, D., Ziedonis, D.M., 2013. Smoking among individuals with schizophrenia in Korea: gender differences. Arch. Psychiatr. Nurs. 27, 241–245. Kumari, V., Postma, P., 2005. Nicotine use in schizophrenia: the self medication hypotheses. Neurosci. Biobehav. Rev. 29, 1021–1034. Li, C.X., 2006. Exploring the Relationship among Smoking Schizophrenia and Related Neurocognitive Functions and a Pilot Molecular Genetic Study. Huaxi Mental Health Centre, Sichuan University, Sichuan (in Chinese). Liu, Q., Yang, X.J., He, S.L., Li, C.L., Yang, J., 2011. The effects of smoking on male schizophrenia patients. Sichuan Ment. Health 24, 35–37 (in Chinese). Ma, X., Xiang, Y.T., Cai, Z.J., Li, S.R., Xiang, Y.Q., Guo, H.L., Hou, Y.Z., Li, Z.B., Li, Z.J., Tao, Y.F., Dang, W.M., Wu, X.M., Deng, J., Lai, K.Y., Ungvari, G.S., 2009. Smoking and psychiatric disorders in the rural and urban regions of Beijing, China: a community-based survey. Drug Alcohol Depend. 100, 146–152. Roick, C., Fritz-Wieacker, A., Matschinger, H., Heider, D., Schindler, J., Riedel-Heller, S., Angermeyer, M.C., 2007. Health habits of patients with schizophrenia. Soc. Psychiatry Psychiatr. Epidemiol. 42, 268–276. Tang, W., Wen, N., Liu, J.H., 2014. A survey on the reasons of smoking and nicotine dependence in patients with schizophrenia , Zhejiang. Prev. Med. 26, 253–256 (in Chinese). Tang, Y.L., George, T.P., Mao, P.X., Cai, Z.J., Chen, Q., 2007a. Cigarette smoking in Chinese male inpatients with schizophrenia: a cross-sectional analysis. J. Psychiatr. Res. 41, 43–48. Tang, Y.L., Gillespie, C.F., Epstein, M.P., Mao, P.X., Jiang, F., Chen, Q., Cai, Z.J., Mitchell, P.B., 2007b. Gender differences in 542 Chinese inpatients with schizophrenia. Schizophr. Res. 97, 88–96. Umene-Nakano, W., Yoshimura, R., Hoshuyama, T., Yoshii, C., Hayashi, K., Nakano, H., Hori, H., Ikenouchi-Sugita, A., Katsuki, A., Atake, K., Nakamura, J., 2013. Current smoking rate in patients with psychiatric disorders in Japan: questionnaire survey. Psychiatry Res. 210, 268–273. von Elm, E., Altman, D.G., Egger, M., Pocock, S.J., Gotzsche, P.C., Vandenbroucke, J.P., 2007. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies. PLoS Med. 4, e296. Zhang, R., Cao, Q., Lu, Y., 2014. The analysis of cigarette smoking behaviors and its influecing factors among Chinese urban and rural residents. Acta Univ. Med. Nanjing (Nat. Sci.) 34, 84–89 (in Chinese). Zhang, X.Y., Chen da, C., Xiu, M.H., Yang, F.D., Haile, C.N., Kosten, T.A., Kosten, T.R., 2012. Gender differences in never-medicated first-episode schizophrenia and medicated chronic schizophrenia patients. J. Clin. Psychiatry 73, 1025–1033. Zhang, X.Y., Xiu, M.H., Song, C., Chen da, C., Wu, G.Y., Haile, C.N., Kosten, T.A., Kosten, T.R., 2010. Increased serum S100B in never-medicated and medicated schizophrenic patients. J. Psychiatr. Res. 44, 1236–1240.