INTRODUCTION: Schizophrenia patients have social cognition deficits as compared with normal individuals in the following key domains identified by the National Institute of Mental Health (NIMH) Consensus Committee: Emotion Perception and Processing, Social Perception and Knowledge, Attributional Bias, and Theory of Mind. Many recent studies demonstrated that patients with schizophrenia have impairments in a wide range of social cognitive abilities, including recognizing emotions from facial expressions, mentalizing, and social decision-making1 . It is understood that these impairments are structural features of schizophrenia associated with specific symptoms and significantly affect cognitive patients’ functioning. Emotions are processes mostly reflected in the facial expressions. Perception and recognition of facial emotional expressions is one of the basic social-cognitive skills for people to guide social functioning and behavior. Interpersonal relationship, conflict and social agreement are extensions of this basic function. In patients with schizophrenia, problems in the capture of social hints and the perception of emotions in people’s faces are associated with impaired social functioning2 . It is thought that important clinical schizophrenia-specific outcomes (social withdrawal, development of delusions, connection with cognitive processes) may be determined by identifying difficulties in the recognition skills of facial expressions and emotions in schizophrenic disorders. It is well known that the frequency of cigarette smoking in schizophrenic patients is higher than in the normal population and the cessation of smoking is more difficult for these individuals. Also, in numerous studies, it has been demonstrated that nicotine administration or smoking provide beneficial effects with neurocognitive deficits, in particular attention and memory in patients with schizophrenia. However, there is no sufficient data assessing the effects of nicotine on social cognition in the literature yet. The objective of the present study was to investigate whether there are differences in social cognitive functions of smoker and nonsmoker patients with schizophrenia by evaluating their facial emotion recognition ability. Considering the previous studies revealing the efficacy of nicotine on cognitive functioning in general, we expected that non-smoker schizophrenia patients would perform worse in facial emotion recognition than the smoker group.
METHODS:
Participants: The study group consisted of 58 smokers (18 female, 40 male; mean age: 35.32±8.26; education level: 9.36±3.12 years) and 40 non-smokers (18 female, 22 male; mean age: 35.17±7.35; education level: 9.00±2.99 years) patients diagnosed with schizophrenia (SCZ). The total of 98 volunteers were in a follow-up program at Sakarya University Education and Research Hospital (35 outpatients and 23 inpatients with SCZ smokers; 28 outpatients and 12 inpatients with SCZ non-smokers).
Assessment: Both groups were evaluated by using the Positive and Negative Syndrome Scale (PANSS) which is a well-known semi-structured interview assessing a wide range of symptoms in schizophrenia. The test includes ‘positive’, ‘negative’ and ‘general psychopathology’ symptom sub-scales. All participants were administered the Facial Emotion Recognition Test which included 56 photos of four males and four females with six facial emotions (happy, sad, fearful, angry, surprised, disgusted) and neutral facial expression from Ekman & Friesen’s series “Pictures of Facial Affect”. At first, the test had a trial section which was composed of the first seven photos that included each emotional facial expression (i.e., angry, sad, happy, neutral, fearful, disgusted and surprised). Then, 49 mixed photos were used for the data analyses in the study. In these 56 photos, numbers of expressions were equal for each emotions. In addition, reaction time to each facial pictures was also recorded. In addition, the Fagerstrom Test for Nicotine Dependence (FTND) was used for scoring the smoker participants.
Statistical Analyses: Data were analyzed with the Statistical Package for Social Sciences for Windows (SPSS) version 18.00. Demographic information was analyzed through descriptive statistics. For the analyses of abnormally distributed data, the Mann Whitney U test was used and for normally distributed data, the Independent Sample T test was used for the comparisons. A p value 0.05). Besides, there was no significant difference between groups on ‘positive’ and ‘general psychopathology’ symptom sub-scales, while ‘negative’ symptom sub-scale score was significantly higher in SCZ non-smokers than SCZ smokers. We found that, according to the Facial Emotion Recognition Test, SCZ smokers performed significantly better than SCZ non-smokers in recognizing facial emotions of happy, sad, angry, surprised, disgusted (p<0.05 for each). But there was no significant difference between groups in recognizing the emotion of fearful. In addition, when evaluating the groups in terms of reaction time for each emotion while recognizing them, it was observed that SCZ smokers replied in significantly less time to each facial emotions except for fearful as compared to SCZ non-smokers (p<0.05).
DISCUSSION: In the current study, we aimed to investigate the effects of nicotine on facial emotion recognition ability in smoker and nonsmoker SCZ patients. As a result, statistically significant group differences were found in favor of SCZ smokers for both the accuracy rate of answers to facial emotion recognition and reaction time for emotions. In other words, this study suggests that smoking may contribute to recognize the facial emotions, i.e., social perception and social cognition, in patients suffering from schizophrenia. The results received were in line with our expectations. Also, we found that ‘negative’ symptom sub-scale score was significantly higher in SCZ non-smokers than in SCZ smokers, consistent with the previous studies. There is evidence for an explanation as to how nicotine affects cognitive functions in schizophrenia: decreased levels of alfa7-neuronal nicotinic acetylcholine receptor (a7-nAChR) in the hippocampus and the frontal cortex of schizophrenic patients – the accepted hypothesis is that a7-nAChR has a role in the pathophysiology of cognitive deficits in schizophrenia, and smoking alleviates cognitive deficits in these patients. Besides, there is no direct evidence to explain the impacts of nicotine on social cognition in patients with schizophrenia. A few studies have suggested that the processing of facial expressions may be altered by cholinergic enhancement3 . Functional magnetic resonance imaging (fMRI) studies have shown that nicotine administration induces a dose-dependent increase in neuronal activity in a distributed system of brain regions, including the nucleus accumbens, amygdala, cingulate and prefrontal cortex. According to the imaging studies, amygdala, superior temporal gyrus and fusiform gyrus come to the fore among brain regions related to face and emotion recognition4 . While the amygdala is related to both face and emotion recognitions, it has been found that the superior temporal gyrus is more sensitive in recognizing emotions and the fusiform gyrus is more sensitive in recognizing the faces. In addition, it is indicated that the amygdala has an indirect connection with the dorsolateral prefrontal cortex working memory-related brain region. In other studies, it is suggested that the impairments in face and emotion recognition are associated with amygdala volume loss, amygdala damage, and hippocampus volume loss. In light of this knowledge, it can be thought that nicotine contributes to positive effects on social cognition by inducing neuronal activity in the amygdala, hippocampus and dorsolateral prefrontal cortex. In the literature, although the connection between social cognition and neurocognition has not yet been exactly clarified, the general impression is that they are related but separate constructs. In addition, previously demonstrated more clearly positive effects of nicotine on neurocognitive processes such as working memory, speed of processing and attention were shown to be moderate and relatively consistent relationships with the social-cognitive processes of emotion perception, social perception and theory of mind. In this context, it is emphasized that normal neuro-cognitive function is necessary but not sufficient for good social cognition performance5 . The present study shows that nicotine may facilitate social cognitive processes in patients with schizophrenia. However, it is not clear why social cognition is better in SCZ smokers, whether it is due to a positive contribution of nicotine to overall cognitive functions or a separate healing mechanism of nicotine on social cognition. Thus, this topic can be an interesting focus of future research in schizophrenia, and more studies are needed to clarify the link between domains of social cognition and nicotine administration/use in schizophrenic patients.