Monotherapy with lithium or valproate or respectively combination therapy with quetiapine have similar effect on cognitive functions in Chinese euthymic patients with bipolar disorder: a cross-sectional survey

BIPOLAR DISORDER, MOOD STABILIZERS AND COGNITIVE FLEXIBILITY: TRANSLATIONALLY DISSECTING ILLNESS FROM DRUG EFFECTS

Bipolar disorder (BD) effects on cognition are confounded by the putative cognitive impact of its major pharmacological treatments, given the neurotrophic potential of mood stabilizers, particularly lithium. We examined the area of cognitive flexibility (CF), aiming to disentangle BD from medication effects, using translational methodology. CF was assessed by CANTAB-IED (intra- extra-dimensional shift; Study 1, euthymic BD participants) and its animal analogue (Study 2, rats). Both studies included groups (1) control, (2) lithium, chronic, current treatment (LI-CHRON-C, A: >2 years, N=32; B: 2 months, N=11); (3) valproate, chronic, current treatment (VPA-CHRON-C, A: >2 years, N=30; B: 2 months, N=12). Study 2 included 2 additional groups; Group 4: LI-CHRON-PAST (2 months, stopped 1 month pretest, N=13); Group 5: LI-ACUTE (LI on test days only, N=13). In Study 1, neither total nor stage (discrimination: D; reversal R; intra- extra-dimensional shifts: IED) IED errors differed between groups [(Kruskal-Wallis: H(2, N= 94) 0.95 > p > 0.65]. Similarly in Study 2, errors did not differentiate the 5 pharmacological groups. Differences emerged only between LI-ACUTE and Controls in response latencies (D, R, IED ANOVAS: 0.002 > p > 0.0003; contrasts D, R: p = 0.002, 0.0001). In conclusion, LI and VPA BD patients were indistinguishable from Controls in IED errors, as were animals treated with LI-CHRON, current or past, or VPA-CHRON-C vs Controls. LI-ACUTE treatment produced significant latency deficits vs. Controls. Within the limitations of translational comparisons, our results suggest that the normal CF noted in euthymic BDs is not attributable to mood stabilizer effects.

A focus on valproate and cognitive deficits in Bipolar Disorders: A mini-review: Special Section on "Translational and Neuroscience Studies in Affective Disorders" Section Editor, Maria Nobile MD, PhD

BACKGROUND

Cognitive deficits represent a core feature of Bipolar Disorder (BD), which seem to characterize this disorder regardless of the mood phase. However, the role of pharmacological treatment in determining cognitive alterations is still not clear. Indeed, although drugs improve cognition by targeting mood symptoms, they could also carry their own cognitive side effects. This is true especially for mood stabilizers as they are the most commonly prescribed drugs in patients affected by BD and they are usually administered also during euthymic phases.

METHODS

In this context, the present review aimed at summarizing the results of the studies evaluating the impact of valproate on cognitive functions in patients suffering from BD, as primary or secondary results. The inclusion criteria were met by ten studies. Specifically, we included one double-blind quasi-randomized study and nine cross-sectional or naturalistic studies, which a) used healthy subjects as control group (N = 1), b) compared valproate treated patients with healthy individuals and other treatments (N = 5), and c) compared valproate treated patients just with other treatments, with a specific focus on lithium (N = 3).

RESULTS

Overall the results suggested a negative effect of valproate on cognitive functions in chronically-treated patients affected by BD. Notably, it has been found that the working memory was the most affected cognitive domain.

LIMITATIONS

Few studies directly explored the effect of valproate on cognition in BD.

CONCLUSIONS

These findings seem to suggest that valproate might have a negative effect on cognitive functions, especially on working memory domain. However, the results should be taken cautiously since the limited number of available studies published so far. In conclusion, these evidences seem to point out that the possible cognitive side effects of pharmacological treatments should be carefully taken into account, especially in chronic patients.

Cognitive Impairment in Patients with Bipolar Disorder: Impact of Pharmacological Treatment

Bipolar disorder is an illness characterised by periods of elated and depressed mood. These mood episodes are associated with changes in cognitive function and there is evidence to suggest that cognitive dysfunction persists during euthymia. The extent to which this is a function of the illness or a result of treatment is less clear. In this narrative review, we explore the impact of commonly used medications for bipolar disorder on cognitive function. Specific impairments in executive function and verbal memory have been noted in bipolar disorder. The impact of pharmacological treatments upon cognitive function is mixed with a number of studies reporting conflicting results. Interpretation of the data is further complicated by the variety of cognitive tests employed, study design, the relatively small numbers of patients included and confounding by indication. Overall, there is some evidence that while lithium improves some cognitive domains, it impedes others. Antipsychotics may be deleterious to cognition, although this may relate to the patient population in which they are prescribed. Sodium valproate is also associated with worse cognitive outcomes, while the impact of other antiepileptics is unclear. Overall the quality of evidence is poor and is derived from a relatively small number of studies that often do not account for the significant heterogeneity of the disorder or common comorbidities. The use of consistent methodologies and measures of cognition across studies, as well as in naturalistic settings, would enable more certain conclusions to be drawn.