Openness predicts cognitive functioning in bipolar disorder

Abstract

Objectives

Openness to experience (O) is a well-established personality factor and is associated with cognitive performance. Little is known about the personality-cognitive relationship in bipolar disorder, an illness with significant variability in mood. Cognitive evaluation is essential in psychopathology assessment as it may reflect underlying disease processes and psychosocial functional capacity. Screening using a proxy personality variable may identify those in need of comprehensive cognitive testing. We hypothesized that O and measures of cognition would associate in both the Bipolar Disorder (BD) and healthy control (HC) samples, whereas neuroticism and extraversion would correlate with cognition only in the BD sample.

Methods

Data from a longitudinal study of BD were used to study the association between personality factors and cognitive measures of attention, executive functioning, memory and fine motor skills. Regression analyses were used to determine the variables that account for the association between personality and cognition.

Results

Aspects of O explained significant cognitive variance (~5%) in both groups; this persisted when demographic variables (including BD versus HC status) were considered. Neuroticism and extraversion did not consistently correlate with cognitive performance in either group.

Limitations

There were more females in the HC group who were slightly younger compared to the BD group. We lack direct measures of positive affect, and there is a reliance on a single measure of personality.

Conclusions

BD Individuals scoring low on self-reported Openness are potential candidates for more comprehensive cognitive assessments (which represent a limited resource).

Introduction

Cognitive functioning is empirically and intuitively important in bipolar disorder (BD), especially given that objectively measured cognitive functioning is consistently poorer in individuals with BD than in unaffected healthy control individuals (HC). Individuals with BD have significant problems with general functioning, including occupational functioning and social adjustment (Macqueen et al., 2001). Cognitive performance is a significant predictor of psychosocial functioning and disability in BD (Depp et al., 2012, Sanchez-Moreno et al., 2009); the relation between functioning and cognition extends to a number of areas including employment (Bearden et al., 2011, O’shea et al., 2010, Ryan et al., 2013) social functioning (Laes and Sponheim, 2006), and observational, objectively scored ratings of performance of instrumental activities of daily living (e.g., writing a check, meal preparation) (Gildengers et al., 2013). Cognitive differences between BD and HC are found in the areas of learning and memory, sustained attention, and executive skills such as planning, task initiation and switching, and inhibition (Boland and Alloy, 2013).

Though an effective indicator of functional status, a full assessment of cognitive functioning is impractical in typical clinical appointments due to time constraints. Furthermore, many cognitive screening measures used in primary care and general psychiatry are inadequate for assessing the relatively subtle cognitive impairment seen in inter-episode bipolar disorder and usually designed to assess for dementia (Huppert et al., 2005). Comprehensive cognitive assessment is available in neuropsychology clinics and includes a set of tasks that can take 2–8 h to administer. Financially and practically, such assessments are administered at best annually, except after a significant functional change or medical cause of cognitive decline. Comprehensive cognitive screening instruments that are comparatively brief, such as the Repeatable Battery for the Assessment of Neuropsychological Status (Randolph, 1998) are good for assessing cognitive problems in BD (Dickerson et al., 2004), but administering such measures requires time and training by specialists that renders them difficult to use in primary care or general psychiatric clinics. Given these limitations, clinical variables associated with cognitive functioning would be helpful for clinicians who wish to have an empirical basis for referring BD patients for cognitive assessment.

Personality measures provide an attractive set of candidate variables for screening of cognitive functions. Personality variables have robust associations with psychosocial functioning (Ro and Clark, 2013), and a number of broad personality traits can be assessed (including by non-specialists) reliably, validly, and quickly via brief self-report measures (Gosling et al., 2003). A large proportion of personality variability is captured in the “Big-Five” Model of personality (e.g., Norman, 1963), which is supported by the empirical literature. The “Big-Five” model refers to a consensus model of personality that includes the domains Neuroticism, Extraversion, Openness to Experience, Agreeableness, and Conscientiousness; it was developed in a non-clinical population but is also valid among individuals with mental health problems (Widiger and Costa, 2012). Furthermore, the “Big-Five” is compatible with other popular higher and lower-order personality models (2005). Openness to Experience (O) refers to a variety of tendencies including curiosity, appreciation for complexity, a desire for variety, esthetic appreciation, imagination and fantasy, and non-traditional values (Connelly et al., 2014). Openness has a well-replicated, moderate relation to cognitive functioning in the general population (e.g., Deyoung et al., 2011, Von Stumm, 2013) and has been found to have genetic relations to cognitive functioning (Wainwright et al., 2008).

Mood is a salient feature of BD, and it is intuitive to attribute cognitive dysfunction among individuals with BD to extreme mood states. Nonetheless, a number of recent studies have shown that aspects of cognitive dysfunction (e.g, verbal learning and memory, speeded set shifting, and attention) are consistent across bipolar mood states (e.g., Bourne et al., 2013, Mann‐Wrobel et al., 2011, Ryan et al., 2012), though aspects of inhibitory control are related to bipolar mood state (García-Blanco et al., 2013, Ryan et al., 2012). Additionally, the specific cognitive functions that vary with bipolar mood state varies somewhat across studies (Ha et al., 2014). The influence of mood on cognitive performance has not been examined as thoroughly or as comprehensively in healthy samples, but there is mixed evidence for effects of mood on aspects of cognitive functioning (Brose et al., 2014, Carvalho and Ready, 2010, Forgas, 2013, Mitchell and Phillips, 2007, Phillips et al., 2002). In summary, among both BD and HC samples, mood has relations to measured cognitive functions but these effects appear to be somewhat task and sample dependent. Nonetheless, mood continues to be a key feature to assess when examining the relationship between cognition and other important variables.

Despite the mixed evidence for the effect of current mood on cognitive functioning, some personality variables have plausible conceptual links to bipolar severity over time and, thus, may account for cognitive variability among individuals with BD but less so among HC individuals. Specifically, Neuroticism is associated with negative mood, mood lability, mania and depression, and general psychopathology (Markon, 2010). Low extraversion is associated with bipolar and unipolar depression (Lozano and Johnson, 2001, Markon, 2010). In the general population, however, neuroticism and extraversion have limited relations with fluid cognition (e.g., skills similar to various aspects of executive functioning), crystalized cognition (e.g., vocabulary knowledge), and memory (e.g., Auditory Memory, Visual Memory) (Soubelet and Salthouse, 2011). Nonetheless, it is possible some personality traits may be cognitively relevant disease severity markers among individuals with BD but, given previous evidence, are unlikely to explain cognitive variability among HC.

We developed three major hypotheses for the current study: 1: O, especially aspects of O related to interests in problem solving and cognitively demanding hobbies, is a predictor of general cognitive functioning among individuals with BD and HC; 2: Neuroticism would relate negatively to cognition among individuals with BD and; 3: Extraversion would relate positively to cognitive functioning in BD but that these relations would be non-significant among HC.