Schizophrenia is a serious chronic mental illness, and its patient symptoms include hallucinations, negative symptoms, cognitive dysfunction, emotional and social withdrawal(1–3). For such patients, in addition to the barriers in the cognitive field, the impairment of body function caused by this disease may bring lifelong disability(2, 4). Moreover, some addictive behaviors of patients with schizophrenia can increase the burden on the body and bring about more serious adverse outcomes, among them, smoking is a common behavior(5). According to reports, the smoking rate among American adults in 2016 was 15.5%, and this proportion reached 60% among patients diagnosed with schizophrenia(6). In china, it is reported that about 59.1% of Chinese male patients with schizophrenia are associated with smoking behavior(7). At the same time, studies point out that schizophrenia is related to a 20% reduction in life expectancy(8). There is no doubt that tobacco dependence will increase the burden on patients. Compared with non-smokers, tobacco use significantly increases the mortality rate of patients with schizophrenia(9, 10). Therefore, more and more psychiatrists begin to pay attention to the problem of co-disease of schizophrenia and tobacco dependence, but such patients often lack subjective will to quit smoking, and the smoking quitting rate is 50% ~ 90% lower than the general people(11).
Current treatments for schizophrenia include antipsychotic medications and psychosocial interventions(2), but in the same trial, these interventions may only focus on psychiatric symptoms and rarely report their effects on smoking behavior. Repeated transcranial magnetic stimulation (rTMS), as a brain stimulation technique, is used to treat a wide range of neurological disorders(12, 13). rTMS is a non-invasive means of stimulating cortical neurones, it does not require surgery or anesthesia, with long-term development, this technology has more mature implementation specifications and safety guidelines(14). In the implementation of rTMS device, it delivers magnetic pulses into the brain cortex, factors such as coil shape, stimulation location, frequency and intensity, number of trains, duration, sessions, etc. are more common variables, they play a role to modulate cortical activity(15). In addition to some evidences indicated that high frequency rTMS could improve negative symptoms in schizophrenia patients(16), there is also evidence that rTMS over the dorsolateral prefrontal cortex (DLPFC) can affect processes involved in nicotine addiction(16, 17). Therefore, there are some clinical trials exploring the treatment effect of rTMS on smokers diagnosed with schizophrenia, but there is very little evidence to verify the effect of rTMS on both psychiatric symptoms and smoking outcomes of such patients.
Evidence-based research has strongly promoted the development and progress of various disciplines, especially in clinical practice(18, 19).
This study aims to target smokers with schizophrenia, using systematic reviews and meta-analysis methods to comprehensively analyze the treatment effects of rTMS technology on the psychiatric symptoms and smoking behavior of such patients, in order to provide guidance and basis for clinical practice.