A meta-analysis of up-to-date epidemiological studies published in the British Journal of Psychiatry found a lack of certainty regarding the relationship between schizophrenia and lung cancer. Prior research has demonstrated a link between schizophrenia and risk factors for lung cancer, particularly smoking, obesity, physical inactivity, and metabolic disorders.
Chuanjun Zhuo, MD, PhD, of the department of psychiatric-neuroimaging-genetics laboratory, at the Tianjin Anding Hospital in China, and colleagues searched PubMed and EMBASE for English-language prospective or retrospective cohort studies of lung cancer in adult patients with schizophrenia and the general population. They applied a random-effects model and prediction interval to determine heterogeneity; evidence quality was also assessed.
The investigators identified 12 studies (N=496,265 patients) for meta-analysis. The data demonstrated no association between schizophrenia diagnosis and lung cancer incidence compared with the overall population (standardized incidence ratio, 1.11; 95% CI, 0.90-1.37; P =.31). In secondary analyses stratified by gender, the results were similarly negative.
There was significant heterogeneity (I2, 94%; P <.01) among the various studies and considerable between-study variance with wide prediction interval values (0.47 to 2.64). Furthermore, the quality of the evidence was considered very low, although the researchers found no evidence of significant publication bias.
The investigators noted that each original study may not have adjusted for lung cancer-related risk factors such as tobacco smoking and that analysis of the association between schizophrenia and lung cancer risks may have confounded the results. Other confounding factors such as body mass index, occupation, and diet also may have affected the association between schizophrenia and lung cancer.
The researchers suggested that future studies evaluating schizophrenia and lung cancer risk account for all associated risk factors both in the patient cohort and controls. They also called for future studies to determine the relationship based on genetic and biologic functional associations.
Zhuo C, Zhuang H, Gao X, Triplett PT. Lung cancer incidence in patients with schizophrenia: meta-analysis. Br J Psychiatry. 2019;215:704-711.