**7. Conclusion**

Patients with mental illnesses are more associated with high rates of smoking than the general population and are the main consumers of tobacco products. People with mental health conditions smoke substantially and thus they are more at risk of smoking-related morbidity and mortality. However, some hypotheses illustrate the relationship between smoking and mental health, and underlying factors driving the high prevalence of smoking in this group, including self-medications, shared genetic vulnerability in smoking. And also smoking may play role in the development of mental illness because smoking has an elevating effect on negative symptoms. Moreover, nicotine addiction appears when smokers depend on the effect of smoking to improve mood and mitigate withdrawal symptoms. Despite the benefit of smoking in mental health patients, smoking tends to harm patients' physical and mental health. Therefore, it is important to examine the underlying mechanism in order to understand the link between smoking and mental illness. It is also crucial to encourage smoking cessation because it can lead to significant improvement in mental health and physical health. Smoking intervention that combines pharmacological and behavioral support is more effective in the general population in comparison to people with mental health conditions. It is also essential to develop a program that promotes a healthy lifestyle as well as improves mental health among people with mental illnesses. Nevertheless, further research is required to examine the effectiveness of smoking treatment in a patient with a mental disorder.
