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Executive dysfunction and neurological soft signs in patients with schizophrenia and bipolar affective disorder: A descriptive cross-sectional research
, Ilham Zaidi3, Soumitra Das4, Varghese P Punnoose5, Fahimeh Saeed6,, Sumesh T. P7
* Corresponding author: Dr. Fahimeh Saeed, Department of psychiatry, University of Social Welfare and Rehabilitation Sciences, Daneshjo B LV., Tehran, 889912045, Iran. Fasaeed@yahoo.com
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Received: ,
Accepted: ,
How to cite this article: Kartha A, Shoib S, Zaidi I, Das S, Punnoose VP, Saeed F, et al. Executive dysfunction and neurological soft signs in patients with schizophrenia and bipolar affective disorder: A descriptive cross-sectional research. Future Health. 2025;3:69-76. doi: 10.25259/FH_84_2025
Abstract
Objectives
Executive dysfunction and neurological soft signs (NSS) are common features observed in individuals with psychiatric disorders such as schizophrenia and bipolar affective disorder (BPAD). These impairments have significant implications for the functional capacity and quality of life of affected individuals. However, limited research has been conducted on the prevalence of executive dysfunction and NSS in patients with these disorders in the specific context of South India. This study aimed to find the prevalence of executive dysfunctions and NSS in patients with schizophrenia and BPAD.
Material and Methods
This cross-sectional study examined remission characteristics in 40 schizophrenic and 40 bipolar patients using DCR-10 (ICD-10’s criteria for research) in 2015, Kerala, India. Hamilton Depression Rating Scale, Young Mania Rating Scale (YMRS), Mini Mental State Examination (MMSE), Trail Making Test (TMT), Stroop Test (ST), Controlled Oral Word Association Test, Heidelberg manual, PANSS (Positive and Negative Symptoms Scale) applied to Psychiatric evaluations and cognitive assessments. The study sheds light on remission profiles in BPAD and schizophrenia.
Results
Executive dysfunction, defined by abnormal values on the Stroop test (ST), Controlled Oral Word Association Test, and TMT (Trail Making Test), was observed in 20 out of the 40 schizophrenic subjects, representing a prevalence rate of 50%. Additionally, 14 individuals (35%) among the same group exhibited neurological soft signs. Among the bipolar patients, 9 individuals (22.5%) displayed neurological soft signs, while 12 patients (30%) demonstrated executive dysfunction. These findings highlight the presence of executive dysfunction and neurological soft signs in a significant proportion of the studied schizophrenia and bipolar patients.
Conclusion
This study found a significant prevalence of executive dysfunction and neurological soft signs in both schizophrenia and bipolar patients. Further research and interventions targeting executive functioning and neurological manifestations could potentially contribute to improved outcomes and quality of life for these patients.
Keywords
Bipolar affective disorder; Executive dysfunction; Neurological soft signs
Schizophrenia
INTRODUCTION
Executive function refers to a variety of higher-order cognitive processes, including initiation, planning, hypothesis generation, cognitive flexibility, decision making, regulation, judgment, feedback utilization, and self-perception that are necessary for effective and contextually appropriate behavior.1 It comprises numerous subordinate component cognitive operations like attention and working memory, with working memory perhaps the most important of these.2
The term neurological soft sign was first described in early neuropsychiatric literature.3 Soft signs do not indicate focal neurological disorders. It may refer to behavioral symptoms which are sometimes associated with brain damage, physical findings including contralateral outflow movements, and a variety of non-focal signs like choreiform movements, poor balance, mild incoordination, asymmetry of gait, nystagmus, and persistence of infantile reflexes.4
The impact of impaired cognition in schizophrenia is well known. Research over the last decade has shown that the cognitive dysfunction associated with schizophrenia is associated with significant disability.5 Also, emerging research shows that impaired cognition is also an important factor for executive function in bipolar disorder.6
Cognitive dysfunction in bipolar and schizophrenic patients adversely affects psycho social functioning, insight, and treatment adherence. Small decrements in cognitive functioning may make the difference between everyday life and chronic disability.7
Only a few studies have specifically assessed cognitive impairment in bipolar patients. 30-50% of largely remitted patients fail to attain pre-morbid levels of psycho social functioning, and much of the disability may be linked to the neurocognitive impairment.8
General intellectual functioning is preserved mainly in bipolar affective disorder patients.9 Impairments are limited to the acute episodes and to performance scores. Abnormalities were seen in sustained attention and inhibitory control in bipolar affective disorder, and these persisted even in remission.10
Verbal memory is impaired in euthymic patients, while visuo-spatial memory deficits were variable depending on the tasks used.10-13
All aspects of executive functions like planning, abstract concept formation, and set shifting are reported to be impaired in symptomatic bipolar patients14,15 Performance on executive function tests is sensitive to the presence of even residual symptoms, but it may be normal in fully recovered patients with bipolar affective disorder.10,11,13
Most of the studies regarding executive function in bipolar disorder were conducted in acute symptomatic patients. A study on euthymic patients found that they have executive dysfunction which affected their psycho social functioning. These deficits could indicate trait-dependent neurobiological disturbances associated with the pathophysiology of bipolar affective disorder subjects.16 A recent study of Euthymic bipolar patients showed significantly higher total and subscale NSS (neurological soft signs) and BPAD (bipolar affective disorder) scores than controls, with NSS severity linked to mood stabilizer use and earlier illness onset. A cutoff score of 3.5 on the Neurological Evaluation Scale effectively discriminated patients from cocetntrols.17
Exploring the persistent trait-dependent neurocognitive deficits in euthymic bipolar subjects will help not only to conceptualize the role of neurocognitive dysfunction in the pathogenesis of bipolar affective disorder but also the impact on socio-occupational role functioning and natural course of illness, which in turn will be helpful in refining treatment modules.7
So, the evaluation of executive functions in euthymic phase of bipolar affective disorder patients is the focus of research and debate. This study is aimed at finding the prevalence of executive dysfunction in euthymic phase of bipolar affective disorder patients and its relation with socio-demographic variables.
Hoff et al in 1992 and Saykin et al in 1994 found that considerable cognitive dysfunction is present in many schizophrenic patients as early as the first episode. Follow-up studies by Cohen in 1990 and Goldberg et al in 1993 found no change in the course of the cognitive impairment. The impact of increasing age was found to have a stabilizing effect on cognitive function.18 Rund in 1999 concluded that cognitive deficits are relatively stable over the course of illness.19
Cognitive functioning has a bearing on the functional outcome of schizophrenic illness. The aspects of outcome affected are work performance and community functioning, social problem solving, and social skill acquisition. Changes in neuropsychological performance from the time of hospitalization to a 2-year follow-up found that an unfavorable clinical outcome was associated with marginal changes in neuropsychological performance.7
Cognitive remediation in schizophrenia is now considered an evidence-based intervention: it leads to durable improvements in multiple cognitive domains, and these gains are meaningfully linked to better everyday functioning when designed with core active elements (cognitive exercises, strategy training, therapist support, and transfer to real life).20
Neurological soft signs (NSS) are minor neurological abnormalities and include impairment in functions like sensory integration, motor coordination, and the sequencing of complex motor acts.21 In the Indian context, a recent study of schizophrenia patients showed a significantly higher prevalence of neurological soft signs (NSS) compared to controls, particularly in complex motor acts, sensory integration, and memory. These findings support NSS as stable trait markers in schizophrenia, consistent with prior research. NSS were observed in 68% of patients, most prominently affecting motor coordination, while 73% showed cognitive impairment (MoCA <26). Higher NSS and lower cognition correlated significantly, particularly among patients with predominant negative symptoms and greater illness severity. These have consistently been documented to be present in schizophrenia to a greater extent than in other psychotic conditions.3,22
The cerebellar function abnormalities have been documented in schizophrenia. The concept of ‘cognitive dysmetria’ has been proposed as the fundamental mechanism underlying disorders of emotion and intellect resulting from cerebellar dysfunction in schizophrenic patients.23
Previous studies addressing neurological soft signs in bipolar I disorder differed significantly in methodology. Cases are obtained from different treatment settings, and the sample size in each of the studies was relatively small. Overall, their results have shown that NSS is more prevalent in major affective disorder cases compared to healthy controls.
Boks et al 24 in 2000 reviewed 258 studies to compare the prevalence and pattern of NSS in schizophrenia patients, mood disorders, and healthy controls. They found only 17 studies with valuable data on one or more diagnostic groups addressing this issue. The number of patients in their mood disorder group was so small that they were unable to reach a firm conclusion.
In 2004, Boks compared NSS in mood disorders and schizophrenia. Impaired motor coordination was noted equally in both groups due to cerebellar dysfunction. Movement disorder dimensions are more impaired in schizophrenia.24
From previous studies, it is clear that executive dysfunction and neurological soft signs are seen in schizophrenia and bipolar patients, which have many implications on psycho social functioning.24 Only a few studies have been conducted in the euthymic phase of bipolar disorder and the remission phase of schizophrenia.25 No study could be found that compares these two impairments between schizophrenia and bipolar disorder. So, this study aims to find the prevalence of executive dysfunction and NSS in schizophrenia in remission and the euthymic phase of bipolar disorder. Impairments are also compared between the two disorders, and their relation with socio-demographic variables is also assessed.
MATERIAL AND METHODS
Study design
Descriptive cross-sectional study design for one year in a medical college of Kerala, India, in 2015, after getting approval from the Ethical Board.
Study population
BPAD patients were in remission for at least 6 months, euthymic, Hamilton Depression Rating Scale <8, Young Mania Rating Scale <6.26 Schizophrenia patients were in remission, asymptomatic or had low levels of psychopathology for a minimum period of 6 months, PANSS (positive and negative symptoms scale) score were 3 on items 1 to 3 of the positive subscale and total score<21; on items 1, 4 and 6 of the negative subscales, and total score<21; and on items 5 and 9 of the general psychopathology subscales, and total score<48.27
Sample size inclusion criteria
Forty schizophrenic patients in remission and 40 bipolar patients in remission are attending as outpatients in the psychiatry department. We included 40 patients with schizophrenia and 40 bipolar patients, as this number was practical to recruit while still being large enough to show meaningful differences. With 40 per group, we can reliably detect moderate differences in NSS and cognition between groups, and also examine correlations within each illness group. This balance gives the study both feasibility and statistical validity.
Inclusion criteria:
Age 18-65
Education-completed at least eighth standard
Physically able to participate in the evaluation
Those who can give informed consent
Exclusion criteria:
Mental retardation
Medical comorbidities that incapacitate the subject from undergoing the study
Current and history of Substance abuse
Neurocognitive Disorder or Dementia excluded by clinical examination or MMSE
Tools:
For eligibility assessment
Hamilton Depression Rating Scale (HDRS)26
Young Mania Rating Scale (YMRS)26
MMSE (Mini Mental State Exmination)
For Study,
Trail Making Test (TMT)28
Stroop Test28
Controlled Oral Word Association Test29
Heidelberg manual30
PANSS Scale27
Sampling technique
Data collection
A convenience sampling method was adopted. The patient and relative were informed about the study, and written informed consent was obtained from the patient and the relative. Each subject was evaluated by a proper history, general examination, systemic physical examination, mental status examination, relevant laboratory investigations, and psychometric evaluation, wherever needed. Mini-Mental Status examination was carried out to rule out Neurocognitive Disorder or Dementia. The specially designed proforma to gather the socio-demographic data was completed in each case. Psychiatric diagnosis was arrived at using the Diagnostic Criteria for Research (DCR-10). Two specialists in the department cross-checked the diagnosis. The data anonymity and confidentiality were ensured as per the ICMR guidelines.31
All Schizophrenic patients in remission were assessed with DCR-10 & PANSS scale. A corresponding number of Bipolar patients were selected with DCR-10, HDRS, or YMRS. Each patient was assessed with the Stroop test to study selective attention, COWAT for word fluency, TMT to study speed, attention, mental flexibility, visual search, and motor function, and the Heidelberg scale for testing NSS. The data was collected and tabulated.
Statistical analysis
Analysis was done using computer software, Statistical Package for Social Sciences version SPSS 11.0 (university subscription).
Group comparisons of executive dysfunction (ED) and neurological soft signs (NSS) between schizophrenia and bipolar disorder (BPAD) were performed using the Mann–Whitney U test (since the data were non-parametric).
Associations of ED and NSS with categorical variables such as age group, gender, marital status, religion, and family type were examined using Fisher’s Exact test (chosen due to small cell counts).
A p-value <0.05 was considered statistically significant.
RESULTS
In this study, a total of 80 patients, including 40 diagnosed with schizophrenia and 40 with bipolar disorder, were assessed. Executive dysfunction, characterized by abnormal values on the Stroop test, Controlled Oral Word Association Test, and TMT, was observed in 50% (n=20) of the schizophrenic subjects. Additionally, 35% (n=14) of the schizophrenic patients showed the presence of neurological soft signs. Among the bipolar patients, 22.5% (n=9) exhibited neurological soft signs, while 30% (n=12) had executive dysfunction.
In Table 1, it is shown that among schizophrenia patients, 32.5% (n=13) were aged 18-39years, while for BPAD patients, it was 35% (n=14). The majority of both groups belonged to the 40-65 years age range, with 67.5% (n=27) for schizophrenia and 65% (n=26) for BPAD. Males constituted 60% (n=24) of schizophrenia patients and 67.5% (n=27) of BPAD patients. In terms of marital status, 62.5% (n=25) of schizophrenia patients and 67.5% (n=27) of BPAD patients were not single. Religion was equally distributed among Hindu, Christian, and Muslim denominations, each accounting for 35% (n=14) in both groups. Consanguinity was rare, with only 5% (n=2) in each group. Nuclear family setups were more prevalent, with 67.5% (n=27) of schizophrenia patients and 75% (n=30) of BPAD patients.
| Variables | Schizophrenia | BPAD |
|---|---|---|
| Age | ||
| 18-40 years | 13 (32.5%) | 14 (35%) |
| 40-65 years | 27 (67.5%) | 26 (65%) |
| Sex | ||
| Male | 24 (60%) | 27 (67.5%) |
| Female | 16 (40%) | 13 (32.5%) |
| Marital status | ||
| Single | 15 (27.5%) | 13 (32.5%) |
| Not single | 25 (62.5%) | 27 (67.5%) |
| Religion | ||
| Hindu | 14 (35%) | 14 (35%) |
| Christian | 13 (32.5%) | 13 (32.5%) |
| Muslim | 13 (32.5%) | 13 (32.5%) |
| Consanguinity | ||
| Consanguineous | 2 (5%) | 2 (5%) |
| Non consanguineous | 38 (95%) | 38 (2%) |
| Family type | ||
| Nuclear | 27 (67.5%) | 30 (75%) |
| Joint | 13 (32.5%) | 10 (25%) |
BPAD: Bipolar affective disorder
In Table 2, it is shown that schizophrenia is found to have more executive dysfunction and NSS than BPAD. The difference is significant as found by the Mann-Whitney U test among 27 subjects in the age group 18-39 years; no one was found to have executive dysfunction and NSS. 20 have ED & 14 have NSS in the 40-65 years age group. Fisher’s exact test value: - ED – 0.000, NSS – 0.001
| Tests | BPAD | Schizophrenia | Mann-Whitney U | Significance |
|---|---|---|---|---|
| ST | 31.42 (+- 3.848) | 27.62 (+- 2.931) | 1.5 | 0.000 |
| COWAT | 26.42 (+- 2.021) | 16.30 (+- 2.812) | 0.000 | 0.000 |
| TMT A | 50.92 (+- 6.156) | 70.60 (+- 6.731) | 1.00 | 0.000 |
| TMT B | 100.67 (+- 5.499) | 121.25 (+- 6.025) | 0.5 | 0.000 |
| NSS | 18.67 (+- 1.225) | 27.62 (+- 2.931) | 0.000 | 0.000 |
BPAD: Bipolar affective disorder, ST: Stroop test, COWAT: Controlled oral word association test, TMT-A: Trail making test, part A,
TMT-B: Trail making test, part B, NSS: Neurological soft signs
In Schizophrenia, No significant difference for executive dysfunction and NSS in regard to gender (p value: -0.519, 0.787), Marital status (p value: - 0.327, 0.864), In BPAD, there is significant difference for executive dysfunction and NSS in age group (0.003, 0.016), No difference in gender (0.716, 0.226), marital status (0.418,0.437),
DISCUSSION
Executive dysfunction & neurological soft signs (NSS) are important components of the whole disease process of schizophrenia & bipolar disorder. In some aspects, they are more significant than the classic symptoms of these disorders. NSS & executive dysfunction affect the quality of life. They will influence chronicity, psychosocial functioning, insight, and treatment adherence. Executive dysfunction and NSS in schizophrenia and bipolar disorder were studied previously. However, a combined study has not been conducted. So, this study is designed to find the prevalence and to assess the correlation of these with socio-demographic variables. Also, the dysfunctions are compared between bipolar disorder and schizophrenia.
Among the affected subjects, the Stroop Test scores are significantly less than 40. The findings are consistent with other international studies, which have also shown deficits in ST.28 The trail-making tests also revealed significant differences in the time taken to complete the tests. These findings are also consistent with international studies. The number of words tested under COWAT is significantly reduced in the affected subjects. The results are comparable with other international studies.29
The test findings of the current study suggest that executive functions are significantly impaired in bipolar disorder and schizophrenia patients. These dysfunctions represent impairment in working memory and attention, and other cognitive functions that are necessary for effective and contextually appropriate behavior. The deficits on these tests suggest underlying pathology in the prefrontal and frontal cortex in both psychiatric illnesses.
Heidelberg’s score on neurological soft signs is significantly impaired in some subjects in both groups. The results were comparable to earlier studies.24 This emphasizes that NSS is also an integral part of these disorders. The importance of early detection of NSS lies in its impact on the quality of life of the patients. The loss of skill can cause much occupational impairment.
Executive dysfunction
Among 40 study subjects, 20 patients with schizophrenia and 12 bipolar patients have executive dysfunctions. So, the prevalence of executive dysfunction is 50% in schizophrenia and 30 % in bipolar disorder. The prevalence of executive dysfunction in bipolar disorder matches the previous study conducted by Rubinsztein et al in 2000.13 They have found out the prevalence is 32%. However, the rate of schizophrenia in this study is lower when compared to other international studies. Morice et al in 1990 found that there was impairment in cognitive flexibility in 65% and in forward planning in 75% schizophrenic patients. 94% of subjects had impairment in one or more studies for assessing executive function. The disparity noted in the current study may be due to the small sample size.
The increase in age is positively correlated with executive dysfunction. It may be due to the effect of the duration of the illness on cognitive function. Also, advanced age itself is a risk factor for executive dysfunction. However, some studies, which were conducted by Clarke et al (in 2002), demonstrated sustained deficits in the shortest illness duration and fewest affective episodes in remission of matched control subjects, suggesting that the deficit was an early feature of bipolar disorder.
Most of the patients have an age of onset of illness in their adolescent age group. So, increased impairment in advanced age can be considered due to a longer duration of time spent in episodes. Previous studies also support the same result.
The repeated episodes result in an accumulation of neurobiological abnormalities, and stress-induced hypercortisolemia results in neurotoxicity in hippocampal cells and their connections, decreased glucocorticoid receptors, and eventual cell death. The prefrontal cortex is susceptible to such neurotoxicity because of many glucocorticoid receptors and connections with the hippocampus. This ongoing process is responsible for executive dysfunction.23
Earlier studies in bipolar disorder have reported that residual mood symptoms affect cognitive functioning. The same finding is replicated in this study also16
Executive dysfunction does not seem to be related to other socio-demographic variables like sex, marital status, consanguinity, and family type in both groups.
When comparing executive functions, both schizophrenia and bipolar disorder show a significant difference. Though both groups have impairment, it is more pronounced in schizophrenia. Previous studies comparing executive dysfunction in schizophrenia and other nonorganic psychotic conditions, including bipolar disorder, report more impairment in schizophrenia.32
Neurological soft signs
The prevalence of NSS in schizophrenia is 35%, and in bipolar disorder is 22.5% in this study. These results are less than those of previous studies. It may be due to the smaller sample size. Previous studies have reported a prevalence of neurological soft signs ranging from 50–65%.21,33
The mean NSS total score in schizophrenia in the present study was 27.62 (± 2.93), which is higher than values reported in previous studies using the Neurological Evaluation Scale.34
In this study, there is a correlation between advanced age and NSS in schizophrenia. Lane et al in 1996, Malla et al in 1997 reported that NSS are dependent on age.
Previous studies have demonstrated associations between neurological soft signs, age, and illness characteristics in schizophrenia.35,36
NSS in bipolar disorder is increasing with age and is found to be significant. Mann-Whitney value is 0.003. Adequate data about previous studies is not available. Boks et al in 2000 reviewed 258 studies to compare the prevalence and pattern of NSS.24 However, the number of patients in the bipolar study group was insufficient to conclude. NSS was found to be not correlated with other socio-demographic variables of schizophrenia and bipolar disorder.
Comparative studies have shown that neurological soft signs tend to be more severe in schizophrenia than in bipolar disorder, supporting a dimensional neurodevelopmental model across psychotic disorders.37
The higher prevalence of executive dysfunction and NSS in schizophrenia and bipolar disorder has important clinical implications in India, where limited resources and stigma often constrain functional recovery and rehabilitation. Early identification of these deficits can guide targeted interventions such as cognitive remediation and vocational rehabilitation, which are essential for improving social and occupational outcomes. Integrating such approaches into the District Mental Health Programme and aligning them with the National Mental Health Policy of India (2014) would strengthen recovery-oriented care and ensure that treatment extends beyond symptom reduction towards holistic functioning and social inclusion.33
Limitations of the study
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This study is cross-sectional. A longitudinal study would have helped to know the course of these deficits.
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The sample size was 40 each. A larger sample size is needed to determine the generalizability of these findings.
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The patients were already on medication. Since medication can affect these deficits, it acts as a confounding factor.
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Single-center study and lack of a healthy control group.
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Executive functions were only partially assessed. Tests to assess working memory, planning, set shifting, Fluency and generativity can fill the gap.
Implications of the study
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Current study shows the prevalence of executive dysfunction as 30% and NSS as 22.5% in the euthymic phase of bipolar disorder. The prevalence of executive dysfunction is 50% and NSS is 35% in schizophrenic patients in remission. This shows that even though patients are asymptomatic, they are having deficits that can be easily missed during a routine clinical evaluation.
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Executive dysfunction and NSS can cause significant distress in patients and impairment of occupational and social functioning. The deficits are more disabling than the episode per se. Also, in the case of bipolar disorder, the patients spend most of their time in the euthymic phase.
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Since executive dysfunction and NSS are progressive with age and the disease process, identifying these deficits is very important. It helps us to plan a proper rehabilitation programme for the patients.
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According to the new concept of recovery in schizophrenia, identification and correction of cognitive dysfunctions help in complete recovery from schizophrenia.
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This study also emphasizes the need for research in the development of pharmacological agents that can address cognitive dysfunction and neurological soft signs.
CONCLUSION
In summary, our study assessed 40 patients with schizophrenia and 40 with bipolar disorder. We found that 50% of the schizophrenic patients exhibited executive dysfunction, while 35% showed neurological soft signs. Among the bipolar patients, 30% had executive dysfunction, and 22.5% displayed neurological soft signs. These findings highlight the prevalence of cognitive impairments in both disorders and suggest the importance of evaluating executive function and neurological soft signs in clinical assessments. Screening for executive dysfunction and neurological soft signs (NSS) should be incorporated into routine follow-up of patients with schizophrenia and bipolar disorder, as these deficits are closely linked to functional outcomes. Early detection can inform timely rehabilitation measures, including cognitive remediation and psychosocial interventions, which are essential to comprehensive care and recovery-oriented practice.
Data availability
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
Author contributions
AK: Developed the idea; VPP: Supervised everyone and helped in data analysis; SD, FS, SS, and STP: Helped in data collection, manuscript preparation and analysis.
Ethical approval
The research/study was approved by the Institutional Review Board at Medical College of South India, number B6/14038/2014/TDMC, dated 2020.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
Use of artificial intelligence (AI)-assisted technology for manuscript preparation
The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript, and no images were manipulated using AI.
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