Neurocognitive fi ndings in bipolar disorder: An update

The study of neuropsychological functioning in patients with bipolar disorder is expanding rapidly. Indeed, there was a threefold increase in the number of peer-reviewed publications on this topic from 2005 to 2014, as compared to the preceding decade (Figure 14.1). Although significant increase in publication rate is expected in areas of new exploration, the study of neuropsychological functioning in bipolar disorder is neither new nor dependent upon the development of novel technologies. Rather, this increase in scientific interest is driven by a recognition that poor neuropsychological functioning in patients with bipolar disorder is at least partially independent of mood state (Scott, 1995; Atre-Vaidya et al., 1998; Ferrier et al., 1999; Martinez-Aran et al., 2004b; Thompson et al., 2005), that cognitive problems may contribute significantly to lack of full functional recovery from affective episodes (Dickerson et al., 2003; Martinez-Aran et al., 2004a), that neuropsychological deficits may provide clues into the neurophysiologic and neuroanatomic abnormalities implicated in the pathophysiology of the illness (Sweeney et al., 2000; Soares, 2003), and that neuropsychological dysfunction may be amenable to pharmacological or cognitive remediation (Anaya et al., 2012). Previous studies have demonstrated significant variability in neurocognitive functioning of patients with bipolar disorder, with a subgroup (30-40%) of patients showing little or no evidence of neurocognitive impairment (Altshuler et al., 2004). Conversely, a significant portion of patients with bipolar disorder complain of cognitive difficulties (Burdick et al., 2005; Martinez-Aran et al., 2005). Formal neuropsychological deficits have also been documented in asymptomatic patients who do not complain of cognitive difficulties (Burdick et al., 2005; Martinez-Aran et al., 2005), indicating that neuropsychological impairments may be more widespread than clinical experience would suggest. In this chapter, we review the current literature on the cognition of bipolar disorder. While earlier reviews of this literature have been conducted by our group and others (Bearden et al., 2001; Quraishi and Frangou, 2002; Glahn et al., 2004), the exponential increase in recent publications warrants an updated review and synthesis of the literature. Our review is organized around a set of guiding questions: • Is neuropsychological dysfunction limited to specific cognitive domains in bipolar disorder? • To what extent are impairments explained by current mood state? • Does the course of illness impact neuropsychological functioning? • Is neuropsychological dysfunction in bipolar disorder explained by comorbid psychiatric illnesses (e.g., substance abuse, anxiety)?.