|Year : 2019 | Volume
| Issue : 3 | Page : 141-146
Intercorrelation of symptom dimensions in patients with schizophrenia
Nesrin Elsaadouni1, Haitham Elboraie2, Samah Rabei2, Ahmed Elboraie1
1 Psychiatry Department, Faculty of Medicine, Mansoura University, Mansoura, Egypt
2 Neuropsychiatry Department, Faculty of Medicine, Helwan University, Helwan, Egypt
|Date of Submission||11-Jul-2019|
|Date of Acceptance||22-Jul-2019|
|Date of Web Publication||19-Nov-2019|
MD MRCPsych Samah Rabei
Neuropsychiatry Department, Faculty of Medicine, Helwan University, Helwan, 11727
Source of Support: None, Conflict of Interest: None
Background The heterogeneity of schizophrenia symptoms is well documented. The positive and negative distinction is limited to cover the entire spectrum of schizophrenia phenomenology.
Aim The aim of the study is to find out the major symptom dimensions of phenomenology in a sample of schizophrenic patients.
Materials and methods We recruited 100 schizophrenic patients. Diagnosis was based on diagnostic and statistical manual criteria. Positive and negative symptoms scale was used to assess schizophrenia symptoms. Patients’ scores were subjected to factor analysis with varimax rotation. Internal consistency was determined by the use of Cronbach’s α.
Results Five dimensions (factors) were produced: negative, excitement, positive, depressive, and cognitive dimensions. Internal consistency was quite satisfactory.
Keywords: intercorrelation, symptom dimentions, schizophrenia
|How to cite this article:|
Elsaadouni N, Elboraie H, Rabei S, Elboraie A. Intercorrelation of symptom dimensions in patients with schizophrenia. Egypt J Psychiatr 2019;40:141-6
|How to cite this URL:|
Elsaadouni N, Elboraie H, Rabei S, Elboraie A. Intercorrelation of symptom dimensions in patients with schizophrenia. Egypt J Psychiatr [serial online] 2019 [cited 2019 Dec 13];40:141-6. Available from: http://new.ejpsy.eg.net/text.asp?2019/40/3/141/271302
| Introduction|| |
The turning point adopting the dimensional point of view of symptomatology of schizophrenia came perhaps from the study of Crow (1985), who suggested a new inherent typology of schizophrenia, which integrated clinical presentation, pathophysiology, and treatment response in a single model (Jablensky, 2010). Crow hypothesized two syndromes in schizophrenia type1 with positive symptoms and good response to treatment and type 2 with negative symptoms and poor outcome (Csernansky, 2012). In an other work to identify the latent dimensions of schizophrenia phenomenology Liddle (1987) proposed three syndrome models including psychomotor poverty, disorganization and reality distortion (delusion, hallucinations). The three-dimensional model which embraces positive, negative, and disorganized dimensions has been supported by numerous studies (Ventura et al., 2010).
However, numerous later studies have established more than three symptom dimensions. Kay and Sevey (1990) obtained a model which includes four dimensions (of which positive, negative, hostile/excited, and depressed) formed a four-factor pyramidal model. Another factor analysis has produced a five-dimensional model that consisted of: negative, positive, hostile/excited, cognitive, and depression dimension (Wallwork et al., 2012; Kosgi et al., 2015).
A more recent strategy for addressing the heterogeneity of the phenotype in schizophrenia is the dimensional approach. While categories traditionally arise from disease models, dimensions are often derived from the study of normal psychology; studies of dimensional approaches have shown less concern about identifying the brain–behavior relationships. Dimensions define a group of symptoms that co-occur more often than would be expected by chance alone, but the occurrence is noted through statistical techniques such as factor analysis. While categories classify individuals (what the patient is), dimensions classify symptoms (what the patient has). Therefore, dimensions can overlap within a given individual and be additive (Cuthbert, 2014).
The identification of symptom-based dimensions (factors) within the diagnosis of schizophrenia has led to a number of questions. First, has the distribution of the factor scores been examined adequately in schizophrenia? Second, how useful is the dimensional approach in assessing schizophrenia?
| Materials and methods|| |
This study will be a cross-sectional observational one to fulfill the primary aim of this study through detection and collection of all available symptoms and demographic and some clinical variables and analyzing them statistically.
A convenient sample of patients involved in the study consisted of a total number of 100 inpatients and outpatients recruited from Mansoura University Psychiatry Department.
For all patients’ thorough history and psychiatric examination using a semi-structured interview were done. Clinical diagnosis of schizophrenia was done and confirmed by another one in an independent evaluation. Then a consensus is reached based on diagnostic and statistical manual criteria.
Psychopathology (symptomatology) assessment
Positive and Negative Syndrome Scale (PANSS) is a 30-item rating completed by the researcher. PANSS is specially developed to assess individuals with schizophrenia and is widely used in the research setting.
This scale was designed to assess three main domains: positive (seven items), negative (seven items), and general psychopathology (16 items) using an operationally defined seven-point scale rating is generally based on information related to the past week (1=none and 7=extreme).
Patient score of PANSS were subjected to factor analysis with a Varimax rotation. Internal consistency was determined by the use of Cronbach’s α. External validity of the dimensions derived was investigated by searching for possible correlations between dimensions and demographic and clinical variables by using the Pearson correlation coefficient.
| Results|| |
[Table 1] presents the mean scores, SD, and range on the individual items of PANSS. Positive symptom items, as concluded from the table the highest obtained scores were on the symptoms of delusions (mean=3.35), followed by hallucination (mean=3.05), and the least obtained score was on the hostility subitem (mean=2.07). The highest score obtained on the negative symptom items was on the emotional withdrawal item (mean=2.68) and the minimum was the stereotyped thinking (mean=1.95). Furthermore, lack of judgment (mean=3.69) and disturbance of volition (mean=2.88) were the highest obtained score on the general psychopathology items.
|Table 1 Mean, SD, and range of individual items of Positive and Negative Syndrome Scale|
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The mean PANSS scores of the sample were as follows: PANSS positive subscale is 18.10±6.064 (7.30 score range). PANSS negative subscale is 15.57±8.312 (7–39 score range). PANSS general psychopathology subscale is 36.61±12.277 (16–57 score range).
[Table 2] shows the results of orthogonal rotation of the five-factor solution; the interpretation of the factors were based on loading over 0.55.
|Table 2 Factor analysis of the 30 items of the Positive and Negative Syndrome Scale|
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The first factor (F1) explained 29.11% of total variance. Emotional withdrawal, blunted affect, poor rapport passive social withdrawal, lack of spontaneity of speech and motor retardation were highly loaded (> 0.55) in this factor. It was called negative dimension.
The second factor (F2) explained 15.39% of variance and had a high loading from delusion, hallucination, grandiosity, suspiciousness, and unusual thought contents. It was named the positive dimension.
Excitement, hostility, tension, uncooperativeness, and poor impulse control, loading of this factor explained 6.63% of the variance and was named excitement dimension (F3).
Somatic concern, anxiety, guilt feeling, and depression loaded on the fourth factor which explained 6.52% of the variance, and was named the depressive dimension.
The fifth interpreted factor had the same explanatory power (variability=5.20%). This factor in called cognitive (disorganization) dimension.
[Table 3] shows factor loading.
|Table 3 Factor loading of Positive and Negative Syndrome Scale items in a five-factor model|
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Factor loadings: The factor loadings are the correlation coefficients between the variables (rows) and factors (columns). In this study, loadings should be 0.55 or higher to confirm that independent variables identified a priori are represented by a particular factor ([Table 4]) Variables sharing the same factor loadings were grouped together while factors in which loadings were less than the cut-off score were excluded.
The percent of variance gives the ratio, expressed as a percentage, of the variance accounted for by each component, to the total variance in all of the variables. As noted from [Table 4], the negative symptom dimension had the highest score while the cognitive dimension had the lowest variations. This means that the stability of the negative symptom component was the weakest, while the cognitive factor component was the strongest and the least variable.
Cronbach’s α is a coefficient of reliability. It is commonly used as a measure of the internal consistency or reliability of a psychometric test score for a sample of examinees. Alpha can take on any value less than or equal to one, including negative values, although only positive values make sense. Higher values of α are more desirable, this denotes high reliability and internal consistency. In [Table 4], the internal consistency of the negative factor dimension was 0.79 while that of the positive 0.71 and cognitive factors 0.74.
It is concluded from the [Table 4] above that their sign was a negative one on correlating the positive and the negative symptom dimension which is expected and proves the validity of the factor analysis, indicating that these variables are correlated in a reversed order; this correlation was of statistical significance indicating that an increase in one variable will decrease the other.
| Discussion|| |
The results of factor analysis in this study result in a five-factor model (five dimensions) underlying schizophrenic symptomatology as assessed by the PANSS and using factor analysis. Negative, positive, excitement, depression, and cognitive impairment symptom dimensions emerged.
The internal consistency (Cronbach’s α value) was more than 0.7 for all the components with the exception of the depressive component (0.69). The negative component had the highest consistency. The lower consistency of the depressive component may be due, at least in part, to the small number of items that constituted this dimension.
We compared our results with those of the studies in which factor analysis techniques were conducted on patients assessed by means of the PANSS. Although most studies outlined below used principal component analyses, the differences in rotation techniques and in the rules for determining the appropriate number of factors do not allow direct comparison of the results.
In this study, six highly significant positive correlations are found between the five dimensions of schizophrenia. They are discussed in a descending manner as to the strength of correlation.
First, negative symptoms are positively correlated with cognitive symptoms (r=0.692). This agrees with Buchanan et al. (1999) who explained negative and cognitive symptoms by serotonergic inhibition of dopaminergic dorsolateral prefrontal pathway.
Second, positive symptoms are positively correlated with excitation symptoms (r=0.691). This agrees with Kapur and Remington (2001) who explained positive symptoms and hostility by serotonergic release of dopaminergic mesolimbic pathway.
Third, depressive symptoms are positively correlated with positive symptoms (r=0.423). This agrees with the study of Rajkumar (2015) which states a similar finding.
Fourth, depressive symptoms are positively correlated with cognitive symptoms (r=0.431). This agrees with Buchanan et al. (1999) who explained depressive and cognitive symptoms by serotonergic inhibition of dopaminergic dorsolateral prefrontal pathway.
Fifth, depressive symptoms are positively correlated with excitation symptoms (r=0.383). This agrees with the study of Kanchanatawan et al. (2018) which states a similar finding.
Sixth, excitation symptoms are positively correlated with cognitive symptoms (r=0.285). This agrees with the study of Kanchanatawan et al. (2018) which states a similar finding.
Overall, the findings of the present study suggest that there are five dimensions (factors) underlying schizophrenia phenomenology with an acceptable degree of reliability and external validity. This may support the view that the dimensional in addition to categorical diagnostic approach may offer an informative method in evaluating schizophrenia patients in the community.
The relatively small size of the sample in the present study, cross-sectional design, and the different phases of illness in the studied patients may have contributed to some limitations of this study.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]