While the sample of this research does not meet community sample requirements, its epidemiological and clinical features may make it cannot be a representative sample for bipolar disorder.
The slightly bigger proportion of males than females (53.3% and 46.7%, respectively) is very near to the usual frequency of mood disorders, as bipolar disorders are approximately equally common in males and females with a greater tendency towards hypomanic traits [17, 18].
Most patients were either divorced or single (66.7%). Separate and divorced patients, either as a cause or as a consequence, have the largest rates of mood disorder. Presentation of patients in the unmarried single state can be explained by the early start of the disease which reduces their chance of being accepted for marriage due to the stigma of psychiatric disorders [17, 18].
The sample of this study showed a mean age at onset of the disorder of 31.8 years, which is consistent with other studies [19,20,21]. This, together with the mean duration of illness of 4.7 years and frequent hospitalization, gives an idea about the burden of this disease on the patients and their families especially their caregivers [22, 23].
Neurological soft signs (NSS)
Some researchers propose that NSS reflects a failure in the integration within or between sensory and motor systems [24], while others argue for deficits in neuronal circuits involving subcortical structures (e.g., basal ganglia, brain stem, and limbic system) [25]. Some NSS has been suggested reflecting a more general “latent” neurological dysfunction; their research reinforces the concept of NSS as a marker of disordered neurodevelopment [26].
Although the presence of NSS has been widely documented in schizophrenia, in bipolar disorder, the same has not been achieved. In this research, bipolar patients showed a much worse performance on the NES than control subjects, thus strengthening the hypothesis that NSS can play a part in early identification of the disease, acting as trait markers [26,27,28,29].
From the above results, we can deduce that bipolar disorder, which can be regarded as one of the neurodevelopmental diseases, involves obvious neurological deficits in the neuronal circuits comprising the four categories of NSS, helping early detection of susceptible patients.
Sociodemographic and clinical variables in relation to NSS
In this study, there was no statistically significant gender correlation with NSS prevalence. This may be incompatible with comparable research on schizophrenia and the first psychotic episode, considering male gender as a predisposing factor for NSS development in schizophrenic patients [24, 30]. Also, there was no statistically significant relation between NSS and the age of patients, consistent with comparable NSS research in schizophrenia and psychosis [24, 30].
There was no correlation between the total NSS score and the age of the patients in this research and in accordance with other studies [31, 32]. However, in neuroimaging research, an adverse correlation was discovered between BP age and gray matter volume [33, 34]. These modifications in histopathology could explain the earlier reported rise in NSS by age [35].
No significant correlation existed between total NSS score and gender. Similar findings were recorded [31, 31]. In female bipolar and schizophrenic patients, however, greater NSS scores were discovered [35]. Gender influence on NSS frequency in BP appears to be poorly studied and the findings are contradictory and inconsistent.
In this study, patients with low level of education had significantly higher scores of NSS which is in agreement with other studies [33, 21]. This finding may give a clue to the NSS associating bipolar I disorder most probably as a trait marker [21].
However, Negash et al. have not found such a correlation [29]. Generally, educational failure in BP would be related to cognitive dysfunction rather than to pre-morbid intellectual deficit [29, 34].
No correlation was found between age at onset of BD and the score of NSS, which is consistent with the results of the only study that evaluated this association [35]. This describes the lack of correlation between the NSS and disease length. However, after 2 to 4 years of BD evolution, other trials revealed a reduction in NSS results [36, 37]. In essence, the improvement involved the sensory integration sub-score associated with improving mood symptoms [37].
No correlation existed between the NSS score and mood episode criteria. However, correlations between these state markers and trait markers such as the NSS are difficult to conclude. No correlation was discovered with either the number of episodes or their severity in line with this research [29].
NSS scores did not differ between patients whether treated by antipsychotics or not. This finding is in agreement with the results of other studies [28, 29]. Indeed, NSS are present in patients who have never been treated with antipsychotics and are not induced by antipsychotic medication [31, 38].
Diagnostic performance accuracy of total NSS score
In the assessment of the diagnostic performance accuracy of total NSS score in the current study according to the ROC curve, the total NSS score demonstrated a high accuracy of being able to discriminate euthymic bipolar I disorder patients from healthy controls.
Results in (Table 5) revealed that the best cutoff point for the total NSS score to discriminate euthymic bipolar I disorder from control subjects was more than 3.5. This cutoff point provided sensitivity and specificity of 96.7% and 100%, respectively, positive predictive value of 100%, negative predictive value of 96.8%, and diagnostic efficiency of 98.3% accurate in discriminating between euthymic bipolar I disorder patients from healthy controls indicating excellent diagnostic performance; also, area under the curve was 0.99 which was highly significant (< 0.001).
So, NSS as measured by NES can be considered as a further step in the diagnosis of bipolar I disorder and may be used as organic indicators in these patients which is supported by the study that was done by Noroozian et al. [35].