A narrative review on the association between smoking and schizophrenia symptoms

Abstract

Smoking is commonly observed in patients with schizophrenia (SCZ). However, the relationship between smoking and SCZ-related risk factors remains unclear. In addition, whether smoking works as a self-treatment to alleviate SCZ symptoms is unknown. Our study aimed to investigate the complex relationship between smoking behavior and specific SCZ symptoms. We conducted a literature search on PubMed using the keyword "smoking self-treatment and SCZ" and identified 191 studies. After screening for relevance, 47 studies were included in the study. Most studies confirmed a correlation between smoking status and the severity of negative, positive, and cognitive symptoms in SCZ. In addition, most studies investigated the association between cognitive symptoms and SCZ with inconsistent findings. We confirmed that smoking status is associated with symptom severity, including cognitive, negative, extrapyramidal, and positive symptoms. These findings support the theory of self-treatment and highlight the importance of addressing smoking behavior in SCZ patients.

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REVİEW ARTICLE
A narrative review on the association between
smoking and schizophrenia symptoms
Kadir Uludag* and Min Zhao
Shanghai Mental Health Center, Shanghai Jiao Tong University, School of Medicine, China
Abstract
Smoking is commonly observed in patients with schizophrenia (SCZ). However,
the relationship between smoking and SCZ-related risk factors remains unclear. In
addition, whether smoking works as a self-treatment to alleviate SCZ symptoms
is unknown. Our study aimed to investigate the complex relationship between
smoking behavior and specic SCZ symptoms. We conducted a literature search on
PubMed using the keyword “smoking self-treatment and SCZ” and identied 191
studies. After screening for relevance, 47 studies were included in the study. Most
studies conrmed a correlation between smoking status and the severity of negative,
positive, and cognitive symptoms in SCZ. In addition, most studies investigated
the association between cognitive symptoms and SCZ with inconsistent ndings.
We conrmed that smoking status is associated with symptom severity, including
cognitive, negative, extrapyramidal, and positive symptoms. These ndings support
the theory of self-treatment and highlight the importance of addressing smoking
behavior in SCZ patients.
Keywords: Smoking; Symptom severity; Prevalence; Schizophrenia; Self-treatment
theory
1. Introduction
Individuals with schizophrenia (SCZ) are known to have a higher prevalence of smoking
than the general population[1]. ey smoke heavier and more frequently[2,3] (than the
general population and patients with other psychiatric disorders[4]). Smoking is a risk
factor for various health conditions, such as cardiovascular diseases and cancer[5]. SCZ
and smoking are associated with increased morbidity, mortality, and heritable risks[6,7].
In addition, smoking can aect lipid levels and alter the blood levels of antipsychotic
(AP) medications[8,9]. Furthermore, genetic studies have explored the relationship
between smoking and SCZ symptoms[10]. erefore, addressing smoking behavior in
SCZ is crucial for improving physical and mental health outcomes.
Smoking might be a potential self-treatment for SCZ[11]. For instance, this hypothesis
was raised to elucidate the relationship between smoking and tardive dyskinesia (TD)[12].
Arecent study observed a dierence in negative symptom severity between SCZ patient
groups with or without TD[13]. Another study supports that reduced expression of
nicotinic acetylcholine receptors in SCZ is associated with negative symptoms[14]. It
assumed nicotine might remit the negative symptom severity in SCZ, but the ndings
remain inconsistent[15-18].
*Corresponding author:
Kadir Uludag
(kadiruludag@mails.ucas.ac.cn)
Citation: Uludag K, Zhao M,
2023, A narrative review on the
association between smoking and
schizophrenia symptoms. J Clin
Basic Psychosom, 1(1): 1014.
https://doi.org/10.36922/an.1014
Received: May 30, 2023
Accepted: July 11, 2023
Published Online: August 2, 2023
Copyright: © 2023 Author(s).
This is an Open-Access article
distributed under the terms of the
Creative Commons Attribution
License, permitting distribution,
and reproduction in any medium,
provided the original work is
properly cited.
Publisher’s Note: AccScience
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Journal of Clinical and
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Smoking and schizophrenia symptoms
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In addition to changes in positive and negative
symptoms, patients with SCZ may experience cognitive
improvement from nicotine[15]. e literature on the
relationship between smoking and cognitive symptoms
is inconclusive[17,19]. Alterations in white matter structure
have been linked to nicotine use and SCZ[20,21], indicating
a potential pathway from nicotine, brain, and symptoms.
Correspondingly, cognitive decits may rise aer nicotine
withdrawal[22].
Many studies investigate the potential positive
and negative eects of smoking in many healthy and
psychiatric samples. However, it is crucial to demonstrate
the relationship between smoking status and SCZ-related
risk factors and symptom severity in SCZ patients. e
objective of our investigation is to explore the association
between smoking status and symptoms of SCZ. rough
our study, we aim to gain a better understanding of how
smoking impacts SCZ symptoms and to identify potential
factors that may contribute to this relationship.
2. Methods
PubMed was used to search articles in the literature.
Overall, 191 of the studies were found. Among them, 46
were related to smoking and various SCZ symptoms (e.g.,
positive, negative, and cognitive). e keyword “smoking
self-treatment and SCZ” was used. Animal studies
were included in the study. Articles related to cannabis
smoking, drug use, and smoking cessation were excluded
from the study. Studies consisting of commentary, review,
editorial, and meta-analysis were also excluded from the
stud y.
Most of the subjects were diagnosed according to the
Diagnostic and Statistical Manual of Mental Disorders,
Fourth edition criteria of SCZ. In addition, animal studies
using rats and mice as subjects were included in the study.
3. Results
3.1. Studies comparing smoking and non-smoking
patients
e main results of the study, comparing smoking
status, are presented in Table 1. Among the 46 studies
reviewed, the majority focused on the association between
smoking status and cognitive symptoms. However,
due to inadequate reporting in some studies, including
information on the AP type, dose, and other related
confounding factors, we were unable to incorporate these
parameters in our review. To address the self-treatment
hypothesis of smoking, which is challenging to investigate
in human studies due to ethical regulations, we included
animal studies in our analysis.
3.1.1. Comparison of cognitive symptoms
Numerous studies have investigated the correlation
between smoking and cognitive symptoms. One study
revealed that nicotine consumption may enhance cognition
in patients with SCZ[3,23]. Conversely, some authors have
identied smoking as a detrimental factor for cognition.
For instance, nicotine has been shown to negatively aect
cognitive processes, such as spatial working memory[3].
Furthermore, individuals who smoke have been found
to have lower IQ scores compared to non-smokers[20].
On the other hand, smoking has not been associated
with improved cognitive performance in patients with
treatment-resistant SCZ[17].
According to a few studies, some biological dierences
related to smoking have been identied in animal
models. For instance, nicotine has been shown to reverse
hypofrontality in mice models[24]. Other studies have
reported potential improvements in attention and working
memory due to smoking[25], as well as a positive eect on
divided attention[23].
In addition, research supports the presence of a sensory
gating decit in rst-episode SCZ patients, which was less
pronounced in those who currently smoke[26]. e self-
medication hypothesis proposes that smoking may alleviate
gating decits in SCZ, and it suggests that treatments
targeting genetic dysfunctions in nicotinic-glutamatergic
interactions could improve cognitive decits[27].
3.1.2. Comparison of positive symptoms
e existing literature on positive symptoms of SCZ presents
conicting ndings regarding the associations between
smoking status and the severity of SCZ symptoms. Some
studies have reported a positive association, with smokers
scoring higher on the positive subscale scores compared
to non-smokers[28]. In addition, another study found that
smoker patients had more severe positive symptoms[29].
Conversely, a dierent study demonstrated that the
smokers had lower positive subscale scores compared to
non-smokers[16]. Moreover, there is an evidence suggesting
that tobacco smoking may have an impact on the
development of psychosis[30]. Similarly, a study reported
a correlation between smoking and positive symptoms in
psychiatric patients[31]. However, other studies have failed
to conrm this association, as SCZ patients oen smoke
for reasons unrelated to alleviating psychotic symptoms[32].
3.1.3. Comparison of negative symptoms
ere is a paucity of literature on the relationship between
smoking status and depressive symptoms. Arecent study
found no signicant dierence in depressive symptoms
based on smoking status[29]. Moreover, DMXB-A, a

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Table1. e studies related to SCZ symptoms and smoking found in Pubmed
Study Goal of study Main relevant results
Nicotine reverses hypofrontality in animal models of
addiction and SCZ[24]
e question of whether nicotine can
modify hypofrontality in addiction and
SCZ models remains unresolved.
Administering nicotine could
potentially serve as a therapeutic
approach for treating SCZ.
Nicotine in action: Cigarette smoking modulated
homotopic functional connectivity in SCZ[43]
SCZ patients and healthy subjects
who smoked had decits between
hemispheres.
Smoking aects the regulation of
hemispheric connectivity.
A temporal chronnectomic framework: Cigarette
smoking preserved the prefrontal dysfunction in SCZ[44]
Smoking-related alterations on the
prefrontal dynamics of information
integration were dierent between the
control and SCZ.
Found a smoking-related
preservation eect on disrupted
prefrontal dynamics.
Self-reported motivation to smoke in SCZ is related to
AP drug treatment[36]
Compared smoking motivation in
controls and SCZ patients.
APs may inuence smoking
motivation.
Minimal eects of prolonged smoking abstinence or
resumption on cognitive performance challenge the
“self-medication” hypothesis in SCZ[45]
e self-medication hypothesis by
examining the eects of smoking
abstinence and resumption on cognition
in SCZ patients.
No changes in cognitive test
performance with smoking
cessation.
Tobacco smoking in treatment-resistant SCZ patients
is associated with impaired cognitive functioning,
more severe negative symptoms, and poorer social
adjustment[17]
Compared cognitive performance,
psychotic symptoms, and social
adjustment between tobacco-smoking
TRS patients and non-smoking TRS
patients.
Smoking was not associated with
better cognitive performances in
SCZ patients.
Cognitive performance and smoking in rst-episode
psychosis: e self-medication hypothesis[25]
e relationship between smoking and
symptoms/side eects of medication.
Smoking might improve attention
and working memory.
Tobacco smoking is associated with AP medication,
physical aggressiveness, and alcohol use disorder in SCZ:
results from the FACE-SZ national cohort[46]
e clinical characteristics of smoking
in SCZ.
Patients with tobacco use have
therapeutic specicities.
A test of the cognitive self-medication hypothesis of
tobacco smoking in SCZ[47]
Tested predictions of the cognitive self-
medication hypothesis.
Subjective or objective attentional
benets are unlikely the critical
force of smoking.
Self-reported motivation to smoke in SCZ is related to
AP drug treatment[36]
Evaluated smoking motivation in controls
and SCZ patients.
SCZ patients reported a stronger
motivation to smoke than controls
for reasons related to pleasure
from smoking and the need for
psychomotor stimulation.
Minimal eects of prolonged smoking abstinence or
resumption on cognitive performance challenge the
“self-medication” hypothesis in SCZ[45]
Examined the eects of smoking
abstinence on cognition.
ere were no eects of early
abstinence from smoking on
cognitive measures in smokers with
SCZ.
SCZ and smoking: An epidemiological survey in a state
hospital[48]
Examined whether smoking is related to
SCZ.
SCZ may increase the risk of being
a heavy smoker.
Tobacco smoking is causally associated with AP
medication use and SCZ, but not with antidepressant
medication use or depression[30]
In smokers, heterozygotes and
homozygotes for rs1051730 genotype
had higher smoking intensity than non-
carriers.
Smoking could inuence psychosis
development.
Eects of nicotine on social cognition, social
competence, and self-reported stress in SCZ patients and
healthy controls[49]
Examined the eect of nicotine on social
cognition in SCZ.
No eects of nicotine by enhanced
recognition of facial aect.
Alpha7 nicotinic acetylcholine receptors modulate
motivation to self-administer nicotine: Implications for
smoking and SCZ[50]
e study aimed to investigate whether
blocking α7 nAC1 would enhance the
motivation of rats to self-administer
nicotine during reinforcement.
Found a reduction of α7 nAChR
function as a mechanism for
increased tobacco use in SCZ.
Use of tobacco in SCZ: A double-edged sword[51]Examined the associations between
tobacco and susceptibility to SCZ.
Supports the self-medication
hypothesis.
(Cont’d...)

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Study Goal of study Main relevant results
Does smoking reduce akathisia? Testing a narrow
version of the self-medication hypothesis[52]
Examined whether heavy smoking
reduces akathisia.
e self-medication theory does
not explain the elevated rates of
smoking observed in individuals
with SCZ.
Cognitive performance and smoking in rst-episode
psychosis: e self-medication hypothesis[25]
Examined the dierences in the course of
those decits aer APs.
Smoking may improve attention.
SCZ and smoking: An epidemiological survey in a state
hospital[48]
Determined whether smoking is related
to SCZ.
e relationship between high
doses of neuroleptics and smoking
was observed only in patients
without SCZ.
Preservation eect: Cigarette smoking acts on the
dynamic of inuences among unifying neuropsychiatric
triple networks in SCZ[53]
e study aimed to determine if smoking
could improve the dynamics of networks
in individuals with SCZ.
e investigation of neural
pathways can yield novel insights
into the self-medication hypothesis
in SCZ.
Higher rates of cigarette smoking in male adolescents
before the onset of SCZ: A historical-prospective cohort
study[54]
Investigated the prevalence of cigarette
smoking in adolescents later hospitalized
for SCZ.
Based on data indicating
abnormalities in nicotinic
transmission in patients with
SCZ and their relatives, a higher
prevalence of smoking among
individuals who will later
develop SCZ before the onset
of the illness could suggest a
link between impaired nicotinic
neurotransmission and SCZ.
Psychoactive substance use in specialized psychiatric
care patients[55]
Investigated prevalence and correlates of
substance use among patients.
Patients with SCZ were more oen
daily smokers.
Smoking improves divided attention in SCZ[23]Examined the interactional eects of SCZ
and smoking history on divided attention.
e positive eect of smoking on
divided attention.
Health for smokers with SCZ — a struggle to maintain a
dignied life[56]
Investigated the habits of smokers with
SCZ and smoking in relation to health.
Smokers with SCZ experience
health problems.
Eects of tobacco on AP treatments and their symptoms
in SCZ[32]
Evaluated the prevalence of tobacco in
patients with SCZ and test if smoking
reduces psychotic and extrapyramidal
symptoms.
SCZ patients smoke for reasons
other than reducing psychotic or
extrapyramidal symptoms.
Smoking and cognitive decits in SCZ: A pilot study[42]Among the smokers, the number of
cigarettes smoked per day was associated
with the severity of cognitive symptoms.
Smoking may alleviate cognitive
decits in SCZ by increasing
dopaminergic neurotransmission.
Tobacco and cognitive performance in SCZ patients: e
design of the COGNICO study[57]
Described the methodology used in the
COGNICO study.
e high rates of tobacco use in
patients with mental disorders.
Nicotine use and its correlates in patients with
psychosis[58]
At the beginning of the study and
annually for 5 years, levels of nicotine
usage were assessed in addition to other
pertinent ratings and measurements.
An interpretation of the ndings
is that patients with psychosis fail
to desist from nicotine rather than
experience the positive eects of
the usage.
Dierential sensory gating functions between smokers
and non-smokers among drug-naive rst-episode
schizophrenic patients[26]
e eects of cigarette smoking, without
new acute exposure before testing, on
sensory gating using the P50 auditory
evoked potential in a group of SCZ
smokers and healthy smokers.
Support a sensory gating decit
among rst-episode SCZ patients.
It was less pronounced among
SCZ patients who were cigarette
smokers.
Separate and combined eects of low-dose ketamine and
nicotine on behavioral and neural correlates of sustained
attention[59]
Investigated the separate and interactive
roles of the N-methyl-d-aspartate
receptor and nAChR systems in the
modulation of attention.
Acute alterations and individual
dierences in nAChR function can
moderate glutamatergic-driven
cognitive deciencies in SCZ.
Table1. (Continued)
(Cont’d...)

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Table1. (Continued)
Study Goal of study Main relevant results
Is smoking linked to positive symptoms in acutely ill
psychiatric patients?[31]
e relationship between smoking and
positive symptoms.
In psychiatric patients, smoking is
linked with positive symptoms.
Eects of tobacco smoking and schizotypal personality
on spectral contents of spontaneous EEG[60]
EEG recorded from smokers and
non-smokers students were studied by
parametric spectral estimation.
e changes in spontaneous
EEG-as attributed to smoking-were
observed in the occipital region for
groups of high and low schizotypy
participants.
Initial phase 2 trial of a nicotinic agonist in SCZ[33]e agent 3-(2,4-dimethoxybenzylidene)
anabaseine is a partial alpha(7)-nicotinic
agonist.
DMXB-A that activates alpha-7
nicotinic receptors, improved clinical
ratings of negative symptoms.
Serotonin transporter genotype and depressive
symptoms moderate eects of nicotine on spatial
working memory[61]
Assessed the eects of NRT on SWM
concerning depressive traits and d5-HTT
genotype.
Smoking-deprived smokers
completed the dot recall test of
SWM during counterbalanced and
double-blind nicotine and placebo
testing sessions.
Lack of benecial galantamine eect for smoking
behavior: A double-blind randomized trial in people
with SCZ[62]
Investigated galantamine’s eect on
smoking in people who were smokers.
Galantamine did not demonstrate
a benecial eect on smoking
behav ior.
Nicotine-haloperidol interactions and cognitive
performance in schizophrenics[63]
Investigated the interactions of
haloperidol and nicotine on cognition of
SCZ patients.
Nicotine may improve cognitive
performance.
Nicotine is more addictive, not more cognitively
therapeutic in a neurodevelopmental model of SCZ
produced by neonatal ventral hippocampal lesions[11]
Used a neurodevelopmental model of
mental illness in rats to test whether
nicotine dependence pervades mental
illness.
Developmental cortical temporal
limbic dysfunction may amplify
nicotine’s reinforcing eects.
Chronic nicotine improves cognitive performance
in a test of attention but does not attenuate cognitive
disruption induced by repeated phencyclidine
administration[64]
Examined procognitive eects of
nicotine in a model of SCZ-like cognitive
dysfunction to test self-medication
hypothesis.
Nicotine had procognitive eects.
Chronic nicotine improves short-term memory
selectively in a G72 mouse model of SCZ[65]
Examined the eects of long-term
nicotine on cognition in an animal model
of SCZ susceptibility.
Nicotine improves cognitive
symptoms by facilitating nicotine-
induced α7nACh receptor
activation.
A comparison of smoking behaviors between patients
treated with clozapine and depot neuroleptics[66]
Investigated if there is a dierence in
smoking behavior between patients
treated with clozapine and depot
neuroleptics.
According to measurements
of expired CO levels, patients
treated with clozapine smoke less
than patients treated with depot
neuroleptics.
Nicotine and clozapine eects on attentional
performance impaired by the NMDA antagonist
dizocilpine in female rats[67]
In cognitive impairment of SCZ with the
NMDA antagonist dizocilpine, the eects
of clozapine and nicotine on impaired
attentional hit accuracy were examined.
Supported in the study by the
reversal of the dizocilpine-induced
attentional impairment by nicotine.
Adolescent nicotine sensitization and eects of nicotine
on accumbal dopamine release in a rodent model of
increased dopamine D2 receptor sensitivity[68]
Reported neonatal quinpirole treatment
of rats with a D(2)/D(3) agonist increases
dopamine D(2) receptor sensitivity, which
persists throughout their lifetime.
Neonatal quinpirole boosted
adolescent nicotine sensitization,
accumbal dopamine overow,
and BDNF protein in response to
nicotine.
Schizophrenic patients who smoke have a faster nger-
tapping rate than non-smokers[69]
e hypothesis was tested by investigating
the correlation between smoking status
and nger-tapping rate.
Smokers showed faster nger-
tapping rates than non-smokers.
Nicotine dependence and symptoms in SCZ: Naturalistic
study of complex interactions[70]
High positive symptoms were less
frequent in mildly dependent smokers
than in non-smokers.
Suggest a complex interaction
between nicotine dependence and
nicotine dependence and SCZ
symptoms.
(Cont’d...)

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Study Goal of study Main relevant results
Increased levels of the nicotine metabolite cotinine in
schizophrenic smokers compared to other smokers[71]
Determine if SCZ patients self-administer
more nicotine during smoking than
non-SCZ.
SCZ patients’ higher dose of
nicotine may target dierent
receptors than those activated by
the lower doses self-administered
by most non-SCZ smokers.
Strain-specicity in nicotine attenuation of
phencyclidine-induced disruption of prepulse inhibition
in mice: Relevance to smoking in SCZ patients[27]
Individuals with SCZ may display
elevated rates of tobacco smoking as a
means of self-medicating against decits
in sensory gating.
Treatments targeting genetic
dysfunctions in nicotinic-
glutamatergic interactions would
treat cognitive problems.
Abbreviations: SCZ: Schizophrenia; AP: Antipsychotic, NMDA: N-methyl-D-aspartate.
Table1. (Continued)
nicotinic agonist that targets alpha-7 nicotinic receptors,
has shown promise in improving negative symptoms[33].
Future studies are needed to explore and understand the
relationship between smoking and negative symptoms in
more details.
3.1.4. Comparison of movement disorder
TD is a common movement disorder that can occur in
patients taking both rst- and second-generation AP[34].
One study suggests that nicotinic cholinergic may reduce
dyskinesias[35]. Similarly, another study reported a stronger
motivation to smoke in SCZ patients compared to control
subjects for reasons related to pleasure from smoking and
the need for psychomotor stimulation[36].
4. Discussion
e present review shows that smoking is associated with
the severity of positive, extrapyramidal, negative, and
cognitive symptoms in SCZ. In addition, most studies found
a signicant association between cognitive symptoms and
smoking, indicating the role of dopamine. In addition
to social and environmental factors, smoking might
contribute to the hyperactivation of the inammatory
system observed in SCZ, partially accounting for the
symptom severity. In addition to the duration of smoking,
several factors should be considered systematically in
future studies. Gender, age, duration of illness, detailed
medication, and psychosocial information might play
essential roles and interact with smoking status.
4.1. Gender
Biological, genetic, and social theories have been proposed
to explain the gender dierences observed in smoking
prevalence. Multiple studies have identied a higher
frequency of smoking among males[18,37]. Particularly, the
study by Hou et al. conrmed the hypothesis of a higher
smoking rate in males and reported rates of 53.6% and 4.0%
for men and women, respectively[38]. However, Xu et al.
found that male Chinese patients with SCZ were not more
likely to smoke compared to the general population[39].
Overall, gender is a major confounding factor that can
contribute to inconsistent ndings regarding smoking
prevalence.
4.2. Age
Limited research exists on the relationship between age
and smoking behavior, but certain studies have observed
that the non-smoking group tended to be older compared
to the smoking group[40]. Among men, the highest smoking
rate was observed in the older age category, while the
lowest rate was observed in the younger age category[41].
However, a study conducted in 2012 found that smokers
tended to be younger[18]. erefore, it is important to
consider participants’ age when examining the association
between smoking status and SCZ symptoms.
4.2.1. Positive symptoms
e existing literature yields inconsistent ndings in this
eld. However, most studies have suggested a link between
increased positive symptoms and smoking[28,29]. Smoking
has been linked with positive symptoms in acute psychiatric
disorders[31], which might also inuence the development
of psychosis[30]. Further studies employing a longitudinal
design are needed to investigate the relationship between
positive symptoms and smoking.
4.2.2. Negative symptoms
As we found, the literature in this eld was limited, reecting
a complex and multifaceted relationship. While smoking
may temporarily relieve specic symptoms, it can also
contribute to developing or worsening negative symptoms
over time. us, clinicians must address smoking cessation
as part of a comprehensive treatment plan for SCZ.
4.2.3. Cognitive symptoms
Smoking has been proposed to alleviate cognitive decits
in SCZ by increasing dopaminergic neurotransmission
in the prefrontal areas[42]. e literature on cognitive SCZ

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symptoms and smoking is abundant. e previous studies
have found that nicotine may improve cognitive skills in
SCZ patients[3,23]. On the other hand, several authors have
reported smoking as a detrimental factor. For example,
nicotine may aect specic cognitive decits, such as
spatial working memory[3]. In addition, smokers have
been found to have lower IQ scores compared to non-
smokers[20]. Similarly, smoking has not been associated
with improved cognitive performances in treatment-
resistant SCZ patients[17].
However, in mice models, biological dierences have
been observed. For example, one study demonstrated that
nicotine can reverse hypofrontality[24]. Moreover, another
study suggested that smoking might improve attention and
working memory[25]. Similarly, a positive eect of smoking
on divided attention was found[23].
Furthermore, another study suggests the presence of a
sensory gating decit among rst-episode SCZ patients,
with the decit being less pronounced among SCZ patients
who were current cigarette smokers[26]. is nding aligns
with the hypothesis of self-medication of gating decits
in SCZ through smoking, suggesting that treatments
targeting genetic dysfunctions in nicotinic-glutamatergic
interactions may eectively treat cognitive problems[27].
4.2.4. Extrapyramidal symptoms
TD is a prevalent movement disorder that can occur in
patients taking both rst- and second-generation AP[34].
However, evidence suggests that nicotinic cholinergic
activity may reduce dyskinesias[35]. Similarly, another study
found that SCZ patients reported a stronger motivation to
smoke than controls for reasons related to pleasure from
smoking and the need for psychomotor stimulation[36].
In this context, a self-treatment hypothesis may partially
explain the association between TD and smoking status.
5. Conclusion
e present study has identied an association between
smoking status and symptom severity, particularly in
relation to cognitive symptoms, which may support the
self-treatment theory of SCZ. e presence of signicant
methodological heterogeneity among the reviewed studies
may account for the inconsistent and conicting ndings
observed in the overall analysis.
One notable limitation is the lack of reporting on
smoking frequency, including whether patients were light
or heavy smokers, in the reviewed studies. is lack of
smoking frequency data constitutes a signicant limitation.
Some studies had missing variables, further contributing
to the limitation of the present study. Furthermore, the
reviewed studies do not establish a causal link between
smoking status and symptom severity in SCZ. Furthermore,
the present study is a narrative review that only focused on
articles from PubMed and limited the searched keywords,
excluding keywords such as “cigarette.”
Future studies should aim to incorporate more
balanced variables, taking into account factors such as
gender, age, AP type, AP duration, and other relevant
sociodemographic values. Longitudinal studies are
necessary to explore long-term eects and changes in
SCZ symptoms and smoking frequencies over time.
Furthermore, future studies should focus on investigating
smoking cessation, especially in patients with SCZ. Future
studies should investigate the reasons behind the higher
rates of smoking among individuals with SCZ. Specically,
exploring the underlying motivations and initial desires
to smoke will help test the self-treatment hypothesis of
smoking as a means to alleviate SCZ symptoms. Moreover,
there is a need for in-depth investigations into the eects
of cognitive-behavioral therapy on smoking addiction and
SCZ symptoms.
Acknowledgments
None.
Funding
None.
Conict of interest
No potential competing interest was reported by the
author.
Author contributions
Conceptualization: Kadir Uludag
Writing – original dra: Kadir Uludag
Writing – review & editing: Min Zhao
Ethics approval and consent to participate
Not applicable.
Consent for publication
Not applicable.
Availability of data
Not applicable.
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