Statistical data demonstrate a concurrent rise in smoking prevalence and mental disorders, such as depression and anxiety, which may be attributed to contemporary lifestyle factors, including social media and recent global events. This indicates a potential correlation between these trends, as individuals with mental disorders may engage in smoking as a form of self-medication to alleviate anxiety. However, smoking is harmful and increases the risk of many diseases. Therefore, smoking cessation strategies are increasingly being considered. Nicotine is a naturally produced alkaloid in plants that makes smoking so addictive. Unfortunately, the public’s lack of understanding of the effects of nicotine leads to misleading claims in the public and media about its biological effects. Thus, current narrative literature review is focused on the examination of the biological effects of organic nicotine from various angles, considering the psychological aspects of addiction and the immune system. Analysis of recent data showed that nicotine not only causes addiction but also has therapeutic benefits in certain diseases (depression, anxiety, schizophrenia) and has anti-inflammatory properties (autoimmunity, neurodegenerative diseases), and a deeper understanding and a broader approach to its effects is needed.

Background and Objectives: Tobacco smoking is associated with an increased risk of depression and anxiety symptoms, but it remains unclear whether this relationship differs according to the type of nicotine product used. The increasing popularity of heated tobacco products has created a need to better understand their association with mental health, particularly in comparison with combustible cigarettes. Therefore, this study aimed to compare the prevalence of depression and anxiety symptoms among combustible cigarette (CC) users, heated tobacco product (HTP) users, and non-smokers. Materials and Methods: A cross-sectional study was conducted among 497 adults. Participants were classified into three groups according to their tobacco-use status: combustible cigarette smokers, heated tobacco users, and non-smokers. Depressive symptoms were assessed using the Patient Health Questionnaire-9 (PHQ-9), and anxiety symptoms were assessed using the Generalized Anxiety Disorder-7 (GAD-7). Group differences were evaluated using hierarchical linear regression analyses adjusted for sociodemographic, health, and lifestyle factors. Results: Tobacco-use group significantly improved the model fit for PHQ-9 (ΔR² = 0.0575, p < 0.001) and GAD-7 (ΔR² = 0.0764, p < 0.001). In non-smokers, scores of depression were 3.48 lower than in CC users and 1.42 lower than in the HTP users’ group. In HTP users, these scores were 2.06 lower than in the CC users’ group. Anxiety scores were 3.71 lower in non-smokers than in CC users, and 1.29 lower than in the HTP users’ group. In the HTP users’ group, this score was 2.42 lower than in the CC users’ group. HC3 robust standard errors with 5000-sample BCa bootstrap confidence intervals and reduced-adjustment sensitivity analyses confirmed the primary pattern. Conclusions: Our study results showed that combustible cigarette users had the highest adjusted depression and anxiety scores, HTP users had intermediate scores, and non-smokers had the lowest. In both tobacco-using groups, greater product-specific nicotine dependence was associated with higher PHQ-9 and GAD-7 scores. Further interdisciplinary studies incorporating biomarkers of nicotine exposure, HPA axis function, inflammation, and oxidative stress are needed to clarify whether the observed differences reflect the characteristics of individuals who choose specific tobacco products or are partly attributable to product-specific effects.