Subjective neurocognition and quality of life in patients with bipolar disorder and siblings
Introduction
Bipolar disorder (BD) is associated with significant neurocognitive and functional impairment, even during euthymia (Bourne et al., 2013, Vieta et al., 2013). Patients with BD have worse overall functioning as compared to the general population, especially in certain areas, such as living independently, interpersonal relationships or success at work (Rosa et al., 2010). In BD, functional impairment seems to worsen with more relapses (Rosa et al., 2012). Moreover, longitudinal studies (e.g. Martino et al., 2009, Tabarés-Seisdedos et al., 2008) have concluded that there is a significant correlation between neurocognition and functionality in BD positing that persistent neurocognitive deficits have negative consequences on quality of life (QoL), work capacity, self-esteem and psychosocial functioning. Moreover, persistent neurocognitive dysfunction is among the major predictors of BD patients’ overall functioning (Andreou and Bozikas, 2013, Depp et al., 2012).
However, less is known about the subjective aspects of neurocognitive and social dysfunction, that is, subjective cognitive complaints and QoL of patients with BD. Self-reported cognitive complaints are poorly correlated with objective cognitive impairment (Martínez-Arán et al., 2005, Van Rheenen and Rossell, 2014, Demant et al., 2015, Miskowiak et al., 2016), but both contribute to socio-occupational problems (Jensen et al., 2015). One study (Martínez-Arán et al., 2005) showed that patients with BD who were aware of cognitive deficits had more episodes and an earlier illness onset. Demant et al. (2015) found a correlation between global subjective and objective measures of cognitive dysfunction, suggesting that cognitive complaints do not represent a reliable, proxy measure of cognition per se. The authors further observed that cognitive symptoms were only partially predicted by depressive symptoms. In a large study with remitted patients, more subsyndromal symptoms, hospitalizations, type II BD, and male gender predicted more subjective complaints than objective impairment, whereas the reverse was predicted by higher verbal IQ (Miskowiak et al., 2016).
Most studies focusing on QoL in mental disorders have been performed in patients with schizophrenia. Besides, studies with patients with BD have actually over-estimated the impact of QoL as most of the studies have been performed in late-stage patients (Michalak et al., 2005, Morton et al., 2017). This may be explained at least in part by the long-standing assumption that functional recovery readily followed the remission of acute episodes of BD. However, recent research suggests that QoL should be taken into account in therapeutic efficacy and prognosis (Cardoso et al.,, Sylvia et al., 2014).
Patients with BD tend to report worse QoL than the general population (e.g., Amini and Sharifi, 2012, Brissos et al., 2008). QoL deficits have been associated in particular with subsyndromal, especially depressive symptoms, neurocognitive deficit, as well as recurrences, so that patients with more interepisodic symptoms, cognitive impairment and multiple episodes tend to report poorer QoL (Amini et al., 2012).
Similar, yet milder, neurocognitive deficits have been identified among unaffected relatives of patients with BD (Bora et al., 2009). However, most studies have examined mixed groups of relatives, including offspring, parents, and siblings (Balanzá-Martínez et al., 2008). Compared to offspring, siblings of patients with BD have a lower risk to develop the illness and those who have gone past the peak age of illness onset could be even considered to be resilient to BD. The few studies focused specifically on unaffected twins and siblings have found objective cognitive deficits, mostly in verbal memory, working memory and executive cognition (Christensen et al., 2006, Kulkarni et al., 2010, Bauer et al., 2016). However, to our knowledge, no previous study has assessed subjective cognition in siblings
Moreover, clinical staging models have been proposed to classify patients with BD according to functional disability during the interepisodic period (Kapczinski et al., 2009). According to this model, patients in the early stages of the disorder would have less neurocognitive and functional deterioration than those in the late stages of BD. This model also proposes a latent stage, which includes healthy first-degree relatives of patients with BD, who are predicted to show no deterioration in their neurocognitive and social functioning. However, the latent stage remains as an understudied area of research and, as far as we know, subjective cognition and QoL have not been simultaneously examined in healthy siblings of patients with BD.
The main objective of this study was to compare the subjective cognitive complaints and QoL in euthymic patients with BD-I and their healthy siblings, according to Kapczinski's clinical staging model (Kapczinski et al., 2009, Kapczinski et al., 2014).
Section snippets
Sample
An observational, cross-sectional study was carried out to compare four different groups: euthymic patients with BD-I in early stages of the disorder, without functional impairment; euthymic patients with BD-I in late stages of the disorder, with functional impairment; healthy subjects but at an increased genetic risk for developing the disorder, in this case siblings of patients diagnosed with BD-I (´latent stage´) and genetically unrelated healthy controls without personal or family history
Study sample
The sample consisted of a total of 92 individuals divided into four groups: 25 early-stage euthymic patients with BD, 23 late-stage euthymic patients with BD, 23 healthy siblings of patients with BD and 21 healthy controls. In patients, the median total score of the FAST scale was 32 points.
The sociodemographic and clinical characteristics of the four groups have been reported previously (Tatay-Manteiga et al., 2017) and they are shown in Table 1. Of note, both clinical groups (early and
Subjective cognitive complaints
The present study showed that late stage-patients reported a greater number of neurocognitive complaints compared to early-stage patients. In addition, early-stage patients also had more complaints than controls and siblings, although differences were not significant.
The COBRA scale is a validated and useful instrument to assess subjective complaints in BD and other psychiatric disorders (Rosa et al., 2013). However, no previous studies have used this scale to compare groups of patients with BD
Conflict of interest
This research has not been financed by any institution or pharmaceutical industry, and was carried out during researchers´ free time. Patients were recruited at facilities affiliated with the public health system. The study was approved by the Ethics Committee of Dr Peset University Hospital in Valencia, Spain, and was carried out in accordance with the basic principles of the Helsinki Declaration.
Contributors
Amparo Tatay–Manteiga is the principal investigator in the research and has worked in all phases of the study and manuscript preparation.
Omar Cauli has participated in the design and supervision of the study and edition of the manuscript.
Rafael Tabarés–Seisdedos has participated as a consultant in the study design and edition of the manuscript.
Erin E. Michalak has participated as a consultant in the study design and edition of the manuscript.
Flavio Kapczinski has participated as a consultant in
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