Cognitive complaints may signal depression in bipolar disorder
MedWire News: The severity of depressive symptoms does not account for the recognized discrepancy between self-reported and objective measures of cognition in patients with bipolar disorder, study results show.
However, there was a significantly increased likelihood of patients with depressive symptoms also reporting cognitive complaints.
"Thus, whenever a patient expresses cognitive problems, the clinician should be aware that this patient might be depressed rather than actually objectively cognitively impaired," the team comments.
Cognitive dysfunction is common in symptomatic and euthymic bipolar patients and has been related to treatment non-adherence and worse functional outcome, note Marieke van der Werf-Eldering (University Medical Center Groningen, The Netherlands) and colleagues.
However, in clinical practice there is uncertainty as to whether cognitive complaints correspond to actual cognitive impairment - and the few studies that have been performed show major disparities between the two measures.
"We hypothesized a priori that patients with a higher level of depressive symptoms would not adequately assess their objective cognitive functioning," the researchers comment in the Journal of Affective Disorders.
To investigate, they recruited 108 patients with bipolar disorder, of whom 45 were euthymic and 63 were mildly or moderately depressed.
Subjective, self-reported cognitive complaints were measured using the Cognitive Failure Questionnaire (CFQ), which includes four subscales: memory, distractibility, blunders, and memory for names.
Objective cognition was assessed by clinicians using a full Cambridge Neuropsychological Test Automated Battery (CANTAB) amongst other assessments.
No associations were found between the CFQ total score and total cognitive score in the whole group, as well as in subgroups of depression severity. Also, no associations were found between CFQ subscales and individual cognitive domain scores.
An exception was the CFQ subscale "memory for names," which showed a statistically significant positive association with speed of information processing (clinician-rated), although the correlation coefficient was small.
It could be argued that forgetting people's names leads to social inconvenience and reactions from other persons, leading to a more realistic complaint of memory problems, the authors speculate.
Although depressive symptoms were positively associated with cognitive complaints, the association between cognitive complaints and objective cognitive functioning was not moderated by depressive symptoms.
There is therefore still need for "a valid tool to predict objective cognitive problems from cognitive complaints with the ultimate aim to make burdening and expensive cognitive test batteries redundant," van der Werf-Eldering et al conclude.
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By Andrew Czyzewski