The current study explored clinical and cognitive differences between patients with BD who maintained outpatient status 3 months after discharge from the hospital and patients who were readmitted to an inpatient unit during this period. Group differences emerged on measures marking the severity of the discrete mood episode (i.e., length of hospital stay, psychosis, GAF scores on discharge), but not on measures related to the general course of illness (i.e., age of onset and number of previous psychiatric hospitalizations). Participants who were re-hospitalized suffered from a more severe mood episode leading to the hospitalization. They also performed more poorly on various neuropsychological measures at discharge. The cognitive differences remained significant after controlling for length of hospital stay, psychosis, and GAF scores. Thus, re-hospitalization was associated with the severity of the discrete mood episode and the degree of cognitive impairment during early remission.
The current results are consistent with earlier work showing that markers of episode severity correlate with levels of cognitive impairment at the time of hospital discharge (Levy et al., 2009
). The replication of this finding further supports the hypothesis that a more severe mood episode predicts greater cognitive dysfunction during early mood remission. However, the data offer no insight into possible neurological accounts for this association. From a broader perspective on the course of illness, various markers of illness severity in general, and psychosis in particular, are related to both cognitive dysfunction and readmission (Milkowitz, 1992
; Martinez-Aran et al., 2008
; Tohen et al., 2000
). It is therefore possible that the co-variances among these factors also emerge in the context of a discrete mood episode: patients who suffered a recent episode of psychosis might be more likely to experience greater cognitive deficits and become more vulnerable to relapse.
In the current study, group differences in cognitive functioning were evident in a variety of domains, especially in executive functioning (effect sizes ranged from .72 to 1.25). The large differences between the groups on measures of visual processing/visual memory (i.e., the Rey Complex Figure tests) and Block design (e.g. a measure of fluid intelligence) may also be attributed to disturbances in executive functioning (Somerville et al., 2000
). In BD, disturbances in executive functioning have been tied to difficulties in accomplishing ordinary tasks (Bell-McGinty et al., 2002
; Gildengers et al., 2007
; Martinez-Aran et al., 2007
; Mur et al., 2007
; Mitchell & Miller, 2008
; Royall et al., 2004
). Executive functions have been described as crucial to performing tasks of daily living (Bonnín et al., 2010
; Martinez-Aran, et al., 2007
; Sanchez-Moreno, 2009
; Torres, 2008
) and important to the quality of life of patients (Brissos et al., 2008a
). In addition, research has shown that executive functioning is involved in both behavior and emotion regulation as well as social competence (Riggs et al., 2006
; Zelazo & Cunningham, 2007
). A number of recent investigations reported that adverse life events and disruption in social rhythm, including difficulties in psychosocial functioning, predicted relapse in persons with BD (Altman et al, 2006
; Cohen et al., 2004
; Hosang et al., 2010a, 2010b; Johnson et al., 2008
; Kim et al., 2007
; Malkoff-Schwartz et al., 2000
; Post et al., 2006
; Sylvia et al., 2009
). Thus, problems with executive function may compromise the ability to meet functional and social demands of daily living, and potentially lead to relapse and re-hospitalization.
Several limitations of the current study deserve mention. The sample size is relatively small, and may only offer preliminary results that require replication. In the context of a naturalistic observation, the study did not control for the effects of medications, although groups did not differ with respect to the number of medications taken on the day of testing. The duration of hospitalization may have been affected by confounding factors, leading to premature discharge of patients with longer hospital stays. Recent substance use and SUD more generally may have also affected both test performance and readmission; however, the groups did not differ in ratios of participants who suffered from SUD co-morbidity. In addition, we were unable to determine inter-judge reliability for GAF scores generated by the attending psychiatrist on the unit, as the scores applied to different patients. Despite the longitudinal nature of the study, conclusions about cause and effect are limited. The current study reported no measurement of cognitive and clinical variables post-discharge, and did not control for various additional factors that can account for relapse. To consolidate conclusions, future longitudinal research should assess patients’ stress levels, substance use, sleep patterns, family functioning, and ability to meet the demands of daily living at multiple points in time following hospital discharge. Future investigations should also examine patients’ capacity for emotional regulation in relation to both executive functioning and vulnerability to relapse. Such measurement would permit clearer causal pathways to be drawn between cognitive impairment, functional and emotional regulation difficulties, and changes in BD symptoms. Despite these limitations, this longitudinal study suggests that characteristics of a discrete mood episode predict cognitive functioning during early remission and re-hospitalization.
Finally, the results of the current study carry implications for patient care. Patients who are admitted to the hospital with psychosis, require longer hospital stay to stabilize, receive lower GAF scores, and suffer from significant cognitive impairment at discharge may be at higher risk for re-hospitalization. These patients may be of greater need for a highly supervised post-discharge environment and on-going supportive services. The severity of the mood episode and level of cognitive functioning while in the hospital may inform clinical decisions regarding patient-care post-discharge. For screening purposes, a brief executive battery may be a parsimonious approach to cognitive evaluation upon hospital discharge in routine clinical practice. Future research may attempt to form normative data for episode duration, lingering residual symptoms, and patterns of cognitive deficits during early remission from a mood episode. This information may be useful for making forward prediction of relapse.