Does a history of substance abuse and illness chronicity predict increased impulsivity in bipolar disorder?

Abstract

Background

Impulsivity is a common feature shared by bipolar disorder (BD) and substance use disorder (SUD). SUD and recurrent mood episodes are considered to be risk factors for poor outcome in BD. However, the association between impulsivity, illness chronicity and SUD in BD remains unexplored.

Methods

103 BD patients with and without a lifetime history of SUD (36.82±11.34 years, 40 males) were recruited. Participants completed the SCID interview and were administered measures of impulsivity including the Barratt Impulsivity Scale (BIS) and selected tests of the Cambridge Neuropsychological Test Automated Battery (CANTAB). Hierarchical regression analyses explored the relationship between illness chronicity, SUD, and impulsivity.

Results

Variance in the BIS, number of false alarms on the Rapid Visual Processing task and other impulsivity indicators of the Cambridge Gambling Task (CGT) was not explained by the chosen variables. Only an increased number of commission errors in the negative condition of the Affective Go/No Go task was significantly associated with illness chronicity. Furthermore there was a trend suggesting a relationship between a lifetime history of SUD and increased propensity to risk-taking during the CGT.

Limitations

Potential limitations include medication and patients׳ remission status from SUD.

Conclusions

Contrary to our expectations impulsivity was generally not predicted by indicators of illness chronicity or SUD. While impulsivity could still be a marker of BD that is present before the onset of the disorder, the link between the number of mood episodes and specific indicators of impulsivity may be related to mechanisms of neuroprogression.

Introduction

Bipolar disorder (BD) is a serious mental illness clinically characterized by mood dysregulation, brain abnormalities, and cognitive deficits such as poor response inhibition that in some cases persist during the euthymic and acute phases (Bora et al., 2009, MacQueen et al., 2001, Quraishi and Frangou, 2002). The majority of BD patients also present with additional mental health conditions such as anxiety and substance use disorder (SUD) (Asaad et al., 2014, Merikangas et al., 2007) that are considered to be predictors of poor response to treatment (Swann, 2010) and low remission rates (Ostacher, 2011) in BD and SUD patients.

Impulsivity is a common feature shared by BD and SUD (Powers et al., 2013, Swann et al., 2007) and has been associated with poor cognitive control and disregard of the long-term implications of one׳s behavior, and may therefore result in risky and disorganized behaviors (Evenden, 1999, Moeller et al., 2001). Impulsivity can be considered as being a multidimensional concept and assessed via self-reports and behavioral paradigms. Previous studies showed that the Barratt Impulsivity Scale (BIS) total score (Patton et al., 1995) – a widely used self-rating measure of impulsivity in psychiatry – discriminates well between healthy subjects and euthymic BD patients (Ekinci et al., 2011, Etain et al., 2013). Additionally, BIS scores have been found to be significantly elevated in BD patients with a history of SUD (Etain et al., 2013).

The comparability and equivalence of self-rated and behavioral indicators of impulsivity is still equivocal (for review (Newman and Meyer, 2014)). A study found that euthymic BD patients encountered difficulties on behavioral measures of impulsivity such as the Hayling Sentence Completion (HSCT) and the Iowa Gambling Task (Christodoulou et al., 2006). Furthermore, the BIS score was found to correlate positively with the number of commission errors on the HSCT and the Iowa Gambling task. Two studies using the BIS alongside the Immediate Memory Task–Delayed Memory Task (IMT–DMT) – a modified version of the Continuous Performance Task (CPT) found that while the BIS scores were elevated in BD patients compared to healthy controls (the two studies included euthymic BD and BD patients with SUD respectively), the number of commission errors of the IMT–DMT was comparable between the two groups (Swann et al., 2004, 2003). Thus, not all facets of impulsivity discriminate between BD and healthy controls. Furthermore, the BIS and behavioral tasks may not capture the same aspects of impulsivity and might be differentially related to outcome measures such as the course or duration of the bipolar disorder.

The literature on the relationship between impulsivity, BD, and SUD is sparse, and it is unclear whether impulsivity is a marker of the bipolar disorder or rather the result of neural damage associated with repeated mood episodes and/or drug use. Theories of neuroprogression in mood disorders suggest that ongoing mood episodes lead to a state of chronic inflammation and eventually result in neurocognitive impairment (Berk et al., 2010, Berk et al., 2011, Kapczinski et al., 2008). Abusing drugs has negative effects on the brain reward mechanisms and on the dopaminergic and serotonergic neurotransmitter systems (Koob and Le Moal, 1997) and may induce hazardous reward seeking behaviors and poor decision making (Kirby et al., 2011). Therefore, a positive association between measures of impulsivity and illness chronicity in BD would support the notion that the levels of impulsivity increase as the bipolar disorder progresses. Similarly, a link between increased impulsivity levels and SUD would be related to the deleterious effects of drugs on the brain. By contrast if there was no relation among these measures, prior research would suggest that impulsivity is more likely to be a marker of BD, being present before the onset of the disorder.

Based on the evidence reviewed above the aim of this cross-sectional study is to investigate the predictive power of indicators of illness chronicity such as illness duration and the number of prior mood episodes on impulsivity in BD, and determine whether a history of SUD additionally explains elevations in impulsivity above and beyond indicators of illness chronicity. Further, we aim to determine whether self-ratings (i.e. BIS) and behavioral measures from the CANTAB battery measure heterogeneous or similar facets of impulsivity. Based on the literature we predict that 1. indicators of illness chronicity will explain variance in both self-rated and behavioral impulsivity measures and 2. that a history of SUD will significantly add to this effect.