|Year : 2020 | Volume
| Issue : 3 | Page : 144-148
Cognitive impairment in patients with schizophrenia: A comparative study from western Rajasthan
Nikita Dhaka1, Arpit Koolwal2, Aditi Agarwal3, Ankit Awasthi4, Ghanshyam Das Koolwal2
1 Consultant Psychiatrist, adhar hospital Hisar, Haryana, India
2 Department of Psychiatry, Dr. S. N. Medical College, Jodhpur, Rajasthan, India
3 Department of Psychiatry, Maulana Azad Medical College, New Delhi, India
4 Department of Psychiatry, Government Medical College, Pali, Rajasthan, India
|Date of Submission||24-May-2020|
|Date of Decision||05-Jun-2020|
|Date of Acceptance||20-Jun-2020|
|Date of Web Publication||22-Sep-2020|
Department of Psychiatry, Government Medical College, Pali, Rajasthan
Source of Support: None, Conflict of Interest: None
Introduction: Cognitive impairment is the core feature of schizophrenia (SCZ). The affected individuals exhibit wide-ranging deficits involving multiple domains of cognitive functioning. These deficits are associated with poor functional outcome and residual disability in patients. Substantial literature exists on cognition in SCZ; however, few studies have been carried out on this subject in India and in particular in Rajasthan. Objective: The objective was to evaluate cognitive functions in SCZ patients and to compare these with healthy controls. Materials and Methods: This cross-sectional study was conducted at the psychiatry department of a tertiary care institution on fifty schizophrenic patients and matched healthy controls who fulfilled the inclusion criteria. Diagnosis was made by DSM-V criteria, and symptom severity was determined by the Positive and Negative Symptom Scale. After seeking sociodemographic details, all participants were administered Postgraduate Institute Battery of Brain Dysfunction to assess their cognitive functioning. Data collected were subjected to suitable statistical analysis (mean, standard deviation and Chi-square test). Results: Majority of the schizophrenic patients (56%) were under 35 years of age, were males (70%), were from urban background (66%) and were married (70%). Schizophrenic patients performed poorly on all domains of cognitive functioning, including memory, performance and verbal intelligence and perceptuo-motor skills. Conclusion: The present study reiterated the previous findings of wide-spread, multidomain cognitive impairment in schizophrenic patients. The resultant cognitive profile has important implications for the aetiology and treatment of this major psychiatric disorder.
Keywords: Cognitive impairment, deficits, intelligence, memory, schizophrenia
|How to cite this article:|
Dhaka N, Koolwal A, Agarwal A, Awasthi A, Koolwal GD. Cognitive impairment in patients with schizophrenia: A comparative study from western Rajasthan. Adv Hum Biol 2020;10:144-8
|How to cite this URL:|
Dhaka N, Koolwal A, Agarwal A, Awasthi A, Koolwal GD. Cognitive impairment in patients with schizophrenia: A comparative study from western Rajasthan. Adv Hum Biol [serial online] 2020 [cited 2020 Dec 5];10:144-8. Available from: https://www.aihbonline.com/text.asp?2020/10/3/144/295833
| Introduction|| |
Cognition is the sum total of mental processes that enable us to acquire knowledge and keep us aware of our surroundings, thereby enabling us to make appropriate judgements. Various domains/subdomains generally assessed in cognitive research to characterise specific impairments in different neuropsychiatric disorders include sensation and perception, motor skills and construction, attention and concentration, memory, executive functioning, processing speed and language/verbal skills.
Cognitive deficits lie at the very core of schizophrenia (SCZ) disorder, and these are neither state related nor specific to illness subtypes. Cognitive impairments begin in early ages in SCZ patients, years before the onset of psychotic symptoms. These impairments further deteriorate during early years of life and become substantial after the onset of psychosis. In addition, these deficits persist during periods of remission and remain relatively stable across time in both patients and those at risk for SCZ.,, A strong link exists between cognitive deficits and impairment in several aspects of functioning. The specific cognitive deficits in SCZ patients as described in the literature include impairments of attention, working memory, executive functions, verbal fluency and disturbances in the selection and processing of information.,, There is sufficient evidence that the deficits in these domains cannot be ascribed to the effects of general factors, such as psychopathology and intellectual deterioration or to the side effects of antipsychotic medication.,
Patients with SCZ exhibit cognitive difficulties, which are very similar to those seen in patients with another major psychiatric disorder, bipolar disorder in terms of their profile, although patients with SCZ may have more severe and widespread impairments. Impairments are present in unaffected relatives of patients with SCZ and can serve as an endophenotype for this illness, and is linked to community functioning. A systematic review of meta-analysis found no evidence for progressive deterioration of cognitive functions in SCZ, however, it concluded that cognitive deficits were more severe in patients with early illness onset.
In recent times, cognitive impairment has gained importance in terms of emerging theories on the aetiology and treatment of SCZ. Much research on cognition in SCZ has been done in developed countries where the outcome was found to be poorer than that in developing countries such as India.
Although Indian studies have researched cognition in SCZ patients, they are few in number, and in particular, no such study has been conducted in western Rajasthan. The present study was an attempt to add to literature on this subject matter by evaluating different cognitive domains in detail among patients suffering from this major psychiatric disorder.
| Materials and Methods|| |
After taking approval of the institute's ethical committee, fifty patients of SCZ attending the outpatient department or admitted as inpatients to the Department of Psychiatry at Dr. S. N. Medical College, Jodhpur, Rajasthan, and fulfilling the inclusion criteria (patients aged between 18 years and 60 years, cooperative and able to understand simple instructions, physically as well as mentally capable of completing the questionnaire) were enrolled in the study. A healthy control group of forty people, which were non-blood related to the patients, was enrolled. Written informed consent was taken from all participants.
Sociodemographic details were elicited by a self-designed pro forma. Diagnosis of SCZ was confirmed by a consultant psychiatrist using DSM-V diagnostic criteria. Those patients with Positive and Negative Symptom Scale score >60 were included in the study. Patients with comorbid psychiatric illness, any other current major medical/surgical illness and a history of head injury were excluded from the study. The Postgraduate Institute Battery of Brain Dysfunction (PGI-BBD) has been developed in India by Pershad and Verma. The battery is administered in Hindi and English, and has been validated for use in the Hindi-speaking and English-speaking population. It evaluates five different domains of cognition as follows:
- Memory: The battery contains PGI memory scale (PMS) to assess remote and recent memory, mental balance, attention and concentration, immediate and delayed recall, verbal and visual retention and recognition. The results of all are summed up into PMS score
- Performance intelligence: It is assessed with Revised Bhatia's short battery of performance tests of intelligence, which itself consists of Kohl–Block test and Pass-a-Long test. The scores are summed up as performance quotient (PQ)
- Verbal intelligence: It is evaluated by verbal adult intelligence scale. The score is represented as verbal quotient (VQ)
- Perceptuo-motor-organisation: Two tests were used to assess this domain i.e., Nahor–Benson test (NBT) and Bender Visual-Motor Gestalt test. The perceptual behaviour is regarded here as involving 'sensory reception, organisation and execution'.
The dysfunction score of the above domains/subtests is summed up into dysfunction rating score (DRS). The test–retest reliability over a period of 1 week of PMS ranges from 0.69 to 0.85 for 10 subtests (n = 40) and for the total test about 0.90 (test–retest and split half).
Information so gained and data so collected were subjected to suitable statistical analysis using SPSS version 16.0 for Windows (Chicago, IL, USA). Frequencies with percentages were calculated for nominal and ordinal variables. Chi-square test was used to determine statistical significance (level of significance considered P < 0.05) between patient and control groups.
| Results|| |
The study participants included fifty schizophrenic patients and forty matched healthy controls. Distribution of participants from both groups across different sociodemographic variables namely, age, gender, residence, literacy, occupations, marital status, monthly income and family type was comparable without any significant variance.
[Table 1] describes the sociodemographic profile of SCZ patients. Majority of the patients (56%) were under 35 years of age. Seventy percent of the patients were males. Most of the patients (66%) were from urban background. Twelve percent of the patients were illiterate, whereas none was postgraduate. Fourteen percent of the patients were unemployed, and an equal number of patients were homemakers. Rest of the patients were engaged in different occupations which included service, business, farming and labour. Majority of the patients (62%) had monthly family income >20,000 INR. Seventy percent of the patients were married, while 60% belonged to joint family.
|Table 1: Sociodemographic characteristics of schizophrenia patients (n=50)|
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[Table 2] shows the illness characteristics of SCZ patients. Majority of the patients (82%) did not have family history of the illness. Seventy-two percent of the patients had illness for 10 years or less duration. In 94% of the patients, age at onset of illness was 40 years or less, with 30% of the patients having onset at <20 years of age.
[Table 3] shows the distribution of PGI-BBD scores among SCZ patients and healthy controls. SCZ patients had poor scores on PMS, PQ and VQ than the healthy control group. Patients had higher dysfunction scores on NBT and BBGT. The DRS, which is the sum total of all domains score, was much higher for SCZ group. The difference in each parameter was statistically significant (P < 0.001).
|Table 3: Postgraduate Institute Battery of Brain Dysfunction scores among schizophrenia patients and controls|
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| Discussion|| |
The present study was aimed to assess cognitive functions, including memory, performance and verbal intelligence and perceptuo-motor skills in SCZ patients and to compare these with control group. In addition to this, sociodemographic details and illness characteristics of SCZ patients were also studied. The study was designed in such a way that both the patient group and healthy control group were matched on sociodemographic variables so that the confounding effect of these variables on study finding can be removed.
The lower scores of SCZ patient group on PMS indicate significant memory impairment as compared to the healthy group. This result is similar to that reported by Srinivasan et al., who, in their study on cognition in SCZ, found that patients performed significantly poorer than normal controls on all tests of cognitive functions evaluated – attention, executive function and memory. The findings by Grover et al. and Keefe et al., in their respective studies, are in concurrence with these results., The findings are further supported by Rushe et al., who observed substantial deficits in long-term memory in patients with chronic SCZ. In their meta-analysis, Aleman et al. documented significant, stable and wide ranging memory impairment in SCZ, which was not substantially affected by potential moderating factors such as severity of psychopathology and duration of illness. Krishnadas et al. reported that patients with SCZ showed significant deficits on tests of attention, concentration, verbal and visual memory and tests of frontal lobe/executive function.
In the present study, performance intelligence was assessed by Revised Bhatia's Short Battery of Performance Tests of Intelligence and the scores were summed up as PQ. PQ is a measure of 'Cattell's fluid intelligence', which resides in the non-dominant hemisphere of brain. It was observed that PQ of SCZ patient group is significantly lower than that of the healthy control group. Auster indicated a similar decline in performance tests in SCZ patients. In their study, Ohi et al. documented intelligence decline in SCZ patients by measuring current and premorbid intelligence quotient (IQ). They found that 30% of SCZ patients had normal intellectual performance, whereas approximately 70% of patients showed deterioration of IQ.
VQ indicates the 'Crystallised intelligence of Cattell', which is accounted by the dominating hemisphere of the brain. In the present study, VQ in schizophrenic patients is significantly lower than that in healthy individuals. The finding is supported by Bhattacharyya et al. who reported that patients with SCZ performed poorly in the areas of processing speed, verbal learning, verbal working memory and visual working memory.
Perceptuo-motor skills are frequently screened in organic dysfunctions, however these skills have also been tested in various psychiatric conditions. In our study, the SCZ patients showed a significant decline in their perceptuo-motor skills as compared to healthy group. Biswas et al. also observed significantly greater deficits on scales of IQ, memory and perceptuo-motor skills in childhood-onset SCZ as compared to adolescent-onset/adult-onset SCZ and concluded that the deficits may have been present even before the onset of illness and are results of the underlying brain damage. The studies by Srinivasan et al. and Savla also reported similar findings., The latter also correlated this finding to the day-to-day dysfunction seen in SCZ patients.
Not much of the data is available specifically comparing schizophrenic patients and healthy controls on the scale PGI-BBD. In this comparative study, the tests of neurocognitive functions chosen were based on the findings of earlier studies on patients with SCZ. These studies suggested that a wide range of cognitive functions are affected in this illness, notably attention, memory, reasoning and processing speed.
As both the study groups were matched on sociodemographic variables, it can be said that the difference seen between the patient group and control group cannot be ascribed to any of these variables. The results of the present study suggest that patients with SCZ have impairment on a wide range of neurocognitive functions that depend on frontal and temporal lobes. Apart from genetic factors, which are inherent to disorder, the neurocognitive impairment could also result from poor compliance to antipsychotic medications, as there is some suggestion that chronic neuroleptic administration may improve performance on tasks requiring sustained attention and visuomotor problem-solving abilities.
| Conclusion|| |
The present study reiterated the previous findings of wide-spread, multidomain cognitive impairment in schizophrenic patients. The cognitive deficits carry a significant functional burden and represent an important target for future therapeutic intervention. The future research can be directed towards identifying precise neuroanatomical correlates of specific cognitive deficits so that these abnormal anatomical regions in the brain can be approached by effective psychopharmacological interventions.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]