Executive functions and memory in bipolar disorders I and II: new insights from meta‐analytic results

Abstract

Executive functions and memory in bipolar disorders I and II: new insights from meta-analytic results.Objective: To perform a systematic review and meta-analysis of executive functions (EF) and episodic memory in bipolar disorder (BD). Methods: A literature search was conducted on three electronic databases. Results were combined using random-effects meta-analysis. Results: A total of 126 studies (6424 patients with BDI, 702 with BDII, and 8276 controls) were included. BDI was associated with moderate to large impairments across all cognitive functions and BDII with small-tomedium impairments. Small significant differences were identified between BDI and BDII on all cognitive functions except inhibition. The Trail Making Test (TMT) (g = 0.74, 95% CI: 0.67-0.80), Hayling Test (g = 0.58, 95% CI: 0.34-0.81), Digit Span Total (g = 0.79, 95% CI: 0.57-1.01), and Category Fluency (g = 0.59, 95% CI: 0.45-0.72) tasks were most sensitive to cognitive impairment in BDI. The TMT (g = 0.65, 95% CI: 0.50-0.80) and Category Fluency (g = 0.56, 95% CI: 0.37-0.75) were also sensitive to cognitive alterations in patients with BDII. Conclusion: BD type I was associated with more severe and widespread impairments than BDII, which showed smaller impairments on all functions except inhibition, where impairments were larger. Education and (hypo)manic symptoms should be further investigated in future studies due to their possible influence on the neuropsychological profile of BD. The instruments identified in this review should be considered for inclusion in cognitive assessment batteries in BD. Summations• Patients with BD type I performed worse than control subjects with moderate to large effect sizes, while patients with BD type II showed impairments with small-to-medium effect sizes. Small significant differences were identified between BD types I and II on all cognitive functions except inhibition.• Education, (hypo)mania symptom scores, and lithium use moderated cognitive impairments in BD.• The TMT B, Hayling Test B, Digit Span Total, and Category Fluency were most sensitive to cognitive impairments and to differences between cognitive performance in individuals with BD types I and II. Limitations• Small number of studies involving BD type II. • Large heterogeneity in effect sizes. • Inconsistent reporting of potential moderator variables (mood symptoms, medication use, comorbidities).

Clinical and genetic differences between bipolar disorder type 1 and 2 in multiplex families

“…Until recently, it was thought that both BD subtypes could be classified along a spectrum of the affective disorders defined by the extent and severity of mood elevation (i.e., major depressive disorder (MDD) < BD-II < BD-I). This concept is in line with findings of BD-I patients suffering from more psychotic [3][4][5][6] and melancholic symptoms 3 , more hospitalizations [6][7][8] , and more severe and widespread impairment of cognitive functions 9 . It is also in line with the observation in several previous studies, that risk for either subtype of BD is higher for those with relatives affected by BD-I (compared to MDD and BD-II) 2,10,11 .…”

Executive functioning in psychiatric patients with deliberate self-harm, as compared with a psychiatric and a healthy comparison group

“…This, together with the findings from the regression analysis, makes it difficult to draw clear conclusions with regard to how cognitive flexibility may be more specifically associated with DSH and other BPD features. Furthermore, a majority of the individuals in the DSHgroup, as well as the NDSH-group, suffered from conditions associated with some cognitive deficits also in euthymic states (Cotrena et al, 2020;Koudys et al, 2018;MacQueen & Memedovich, 2017). The proportion of these conditions was not equal in the psychiatric comparison group, which constitutes a limitation for drawing conclusions from this study.…”

“…Therefore, individuals with bipolar type 1 (Dickinson et al, 2017) were excluded. There is also some recent research indicating executive deficits, to some extent, in bipolar type 2 (Cotrena et al, 2020). Since these effects seem to be small or medium sized, we chose to include individuals with this condition in the study.…”

“…Individuals with severe mental health disorders such as psychotic disorders, bipolar type 1, and ADHD were excluded due to the possible detrimental cognitive effects of these disorders. Since there is well-established evidence that deficits in EF also exist in BPD (Koudys et al, 2018;Ruocco, 2005), and to some extent bipolar type 2 (Cotrena et al, 2020), it could be argued that individuals with BPD and bipolar type 2 also should have been excluded. However, if this was done, the representativity would be negatively affected to such an extent that this study could not be considered relevant in a clinical setting.…”

Three‐year longitudinal cognitive functioning in patients recently diagnosed with bipolar disorder

“…In designing future longitudinal studies assessing cognitive change in bipolar disorder, several recommendations are put forth. First, studies should not be limited to patients with bipolar I, as patients with bipolar II also exhibit clinically significant cognitive deficits . This will require studies with larger sample sizes given the increased heterogeneity.…”