**3. Impacts of smoking in mental health conditions**

The high prevalence of cigarette smoking and mental health issues are a major public health concern and the association between smoking and mental illness is considered to contribute to reduced life expectancy, which results in premature death in patients with severe mental health conditions [13, 26]. Smoking is associated with an increased risk of mental illness and early onset of mental health conditions and also increases hospitalization among those with schizophrenia, bipolar disorder, depression, and anxiety [15, 27]. Smoking contributes significantly to the increased risk of tobacco-related diseases and excess death among individuals with mental health conditions, thus this has been connected to one of the main reasons for early death in patients with mental health issues [28]. However, the evidence that suggests cigarette smoking is associated with mental illness has potentially important public health implications; to illustrate this, individuals with mental health disorders might have difficulty quitting smoking and may face a high risk of physical problems due to smoking [29]. Therefore, this population might need a strong intervention to support their efforts to stop smoking and to ensure their conditions are not exacerbating due to quitting. Understanding smoking patterns in mental illness is also critical to developing effective treatment for smoking cessation and reducing negative outcomes.

#### **3.1 Schizophrenia**

Schizophrenia is a serious mental health condition that affects feelings, thoughts, and behavior. This is a chronic and serious mental illness that affects approximately one percent of the general population. Smoking is very common in patients with schizophrenia, which indicates a high rate of smoking compared with the healthy population [30]. Smoking is more likely to be involved in the development of schizophrenia at a younger age, increasing the severity of this condition as well as increasing the number of associated hospitalizations [31]. In addition, schizophrenic patients smoke for a long time, and inhaled tobacco smoke extensively, leading to the concomitant inhalation of a large number of toxic tobacco elements [21]. Consequently, heavy tobacco usage can also contribute to excessive mortality in schizophrenic

### *Smoking and the Association with Mental Health DOI: http://dx.doi.org/10.5772/intechopen.104233*

patients [32]. Notably, as smoking is harmful, heavy smoking might result in a more detrimental impact on health; for instance, schizophrenic patients might experience an increase of positive symptoms and decreased severity of negative symptoms versus non-smokers or light smokers [11, 21, 33]. Similarly, a recent study suggests that tobacco use can reduce the intensity of the extrapyramidal side effects of antipsychotic medication and diminish the cognitive deficits in patients with schizophrenia [21, 32]. Another important association between tobacco use and patients with schizophrenia can be linked to behavioral changes such as poor lifestyle [31].

Although the basic factors driving the high prevalence of smoking in people with schizophrenia remain ambiguous; however, there are different etiologies for high smoking rate and heavy smoking in schizophrenic patients [32]. Firstly, the self– medication hypothesis may provide an explanation, which points out that patients with schizophrenia often smoke to ameliorate the negative symptoms, cognitive impairment, and extrapyramidal side effects of antipsychotic treatment (**Figure 1**) [33]. This hypothesis suggests that neurotransmitter dysfunction such as dopamine, serotonin, glutamine, gamma-aminobutyric acid, and acetylcholine, which is a key pathological factor of schizophrenia, is improved, as smoking stimulates the activities of these neurotransmitters via various mechanisms [32, 33]. Nicotine binds to the central nicotinic cholinergic receptors, triggering the release of neurotransmitters to normalize their dysfunction and improve symptoms that lead to patients continuing smoking. Another mechanism reveals that smoking reduces the amount of the monoamine oxidase (MAO) that normally deactivates dopamine, thus smoking increases dopamine concentration in the brain, which could provide an antidepressant effect [21, 32].

Secondly, the presence of polycyclic aromatic hydrocarbons in tobacco enhances the metabolism of antipsychotic medications leading to reduce the drug concentration in the blood, resulting in some side effects and increasing the requirement for a higher dose [33]. Cigarette smoking has been revealed to lead to an increase in the activity of cytochrome P450 (CYP) enzymes, which are a group of enzymes present in

#### **Figure 1.**

*The mechanism of the self-medication hypothesis. Neurotransmitter impairment is an essential underlying mechanism of schizophrenia. Nicotine binds nAChRs, which release neurotransmitters in the brain to normalize the dysfunction and improve disease. Brown arrows indicate detrimental effects, whilst blue arrows indicate beneficial effects. (Ach, acetylcholine; DA, dopamine; GABA, gamma-aminobutyric acid; GLU, glutamic acid.*

the liver that are involved in drug metabolisms such as clozapine and olanzapine [31]. This is clinically important because it could reduce the efficacy of the drug and lead to poisoning after quitting smoking [21, 31]. In particular, the increase in CYP1A2 plays a significant role in the degradation of these drugs; likewise, smoking also considerably boosts CYP2E1 activity, and both CYP1A2 and CYP2E1 are also responsible for the activation of certain procarcinogenic substances [32].

#### **3.2 Bipolar disorder**

Bipolar disorder is a chronic, episodic mental disorder that has a distinct characteristic of mania, including mood changes, energy, activity, and concentration [34]. There are two types of bipolar disorder: bipolar I, defined as mania alternating with depression, and bipolar II, described as mild mania or hypomania alternating with major depression [34]. Smoking is also frequently prevalent among people with bipolar disorder, who show a higher prevalence of smoking and a lower rate of smoking cessation than the general population and which leads to poor health-related outcomes; for example, the patients with BD can die up to three decades earlier in comparison to the general population [35]. Despite the high rate of comorbidity and related mortality, a recent study focused on smoking individuals with bipolar disorder and examined the relationship between clinical symptoms and public health consequences: including mood symptoms, quality of life, suicidal behavior, and pharmacological implications as well as biological interaction [36]. Tobacco smoking in people with BD is also associated with higher severity of mania and depression, rapid cycling illness, active illness, higher risk of suicidal behavior, and high rate of substance abuse as well as poor outcomes of pharmacological treatment in patients with BD [34, 36].

Furthermore, it was examined whether these patients could be associated with a poor quality of life, which results in a longer duration of illness and early onset of disease as well as a high rate of hospitalization [36]. The quality of life was lower in BD patients physically, mentally, ecologically, and socially compared with non-smokers. In addition, a number of studies have demonstrated that patients with BD have a higher suicide rate than the general population [37]. Although tobacco use is a strong predictor of suicidal behavior after a major depressive episode in BD, it is not definitely the reason that smokers with BD are potentially more likely to attempt suicide attempts; however, it is possible the aggression and impulsive features may cause particular people with BD to display suicidal behavior [36, 37]. Despite the evidence, tobacco use can be independently related to suicidal behavior in BD patients. There is no full understanding of the relationship between smoking individuals with BD and suicide attempts [36].

The relationship between smoking and BD is complex and multifactorial, potentially resulting from biological interaction, genetic and environmental factors. In addition, the association between smoking and BD can be regarded as bidirectional [35]. Therefore, a possible explanation for the high prevalence of smoking in BD patients is that the clinical symptoms of bipolar disorder increase the risk of early initiation and continuation of smoking. The link between smoking and BD may relate to the reduction of serotonin levels in the brain, which results in impulsive and novelty-seeking behavior; similarly, maintenance and recurrence of addictive behavior have been associated with dopamine and glutamine dysfunction [35, 36]. For example, releases of neurotransmitters in the brain have implicated the pathophysiology of BD and are also considered to play a significant role in nicotine dependence [38]. Moreover, tobacco smoking inhibits monoamine oxidase, which is a potential therapeutic effect

#### *Smoking and the Association with Mental Health DOI: http://dx.doi.org/10.5772/intechopen.104233*

of smoking because it enhances the function of neurotransmitters which improves mood and induces feelings of pleasure [35, 36].

In terms of pharmacological impact, smoking harms medication for mental disorders, including schizophrenia, bipolar disorder, and major depression. Consequently, smoking increases the metabolism of many antipsychotic medications through action on cytochrome P450, particularly the CYP1A2 enzyme [35, 36, 38]. This enzyme lowers the concentration of psychotropic medications, including olanzapine, clozapine, haloperidol, and fluvoxamine [35, 39]. Tobacco smoking may reduce the therapeutic benefit of these medications; hence smokers with BD may require an increased dose of these medications to achieve a given level of symptomatic relief [32, 35, 36]. Nevertheless, the side effect of smoking in people who live with BD is considerable, but the negative effect of smoking on such individuals is entirely preventable.

#### **3.3 Depression**

Depression is a common mental health disorder that presents with a wide variety of symptoms, including feeling sadness, loss of pleasure, feeling guilty, fatigue, poor concentration, and difficulty sleeping or oversleeping [40, 41]. Numerous studies have shown a positive relationship between smoking and depression, where smoking seems to increase the severity of the illness [39]. Despite the robust empirical association between smoking and depression, the actual nature of this link is not widely understood. However, the relationship between depression and tobacco smoking is considered to be bidirectional, in which depression may either cause people to smoke or smoking may lead to an increased risk of developing depression [42, 43]. For instance, some studies have also reported that depression is associated with early-onset smoking, while others have suggested that smoking may contribute to the progression of depressive symptoms [6, 22, 43]. In addition, people suffering from depression may smoke excessively and have a low smoking cessation rate relative to the general population [22, 39]. Despite the incentive for people with depression to quit smoking, they are more likely to return to smoking than the general population [44]. Therefore, it is essential to understand the relationship between smoking and depression and to examine the underlying mechanisms of high smoking rates in patients with depression.

There are a number of hypotheses that have been suggested to describe the high rates of smoking in patients with depression and the reason for continuing to do so, as well as a low rate of successful cessation. The self-medication hypothesis states that people with depression smoke to alleviate their symptoms, thus it is reported that symptoms of this condition may lead to increase smoking [39, 44]. Because nicotine may reduce the symptoms of depression in the short-term, long-term nicotine abstinence can lead to the development of withdrawal symptoms such as a depressed mood [44]; similarly, nicotine addiction may be an important factor for the maintenance of mental balance and elucidate why depression may lead the patient to continue smoking for a long time to mitigate their symptoms [45]. Additionally, tobacco smoking tends to have a pharmacological effect on the brain which is similar to that of antidepressant medications, and also helps the person with depression to relax as a stimulant drug [45]. Importantly, the cognitive dysfunction associated with depression is similar to that noted during nicotine withdrawal; therefore, the depressed smoker is exposed to experiencing much greater cognitive impairment than withdrawal-induced impairment, which considers the overlap of cognitive dysfunction due to depression with the cognitive deficit caused by smoking cessation [46]. This means that patients with depression might well continue to smoke to avoid cognitive impairment.
