Executive dysfunction and treatment response in late-life depression

OBJECTIVES

Executive dysfunction in geriatric depression has been shown to predict poor response to antidepressant medication. The purpose of this review is to clarify which aspects of executive functioning predict poor antidepressant treatment response.

METHODS

Literature review.

RESULTS

From our review, the aspects of executive functioning that appear to be associated with antidepressant response rates are verbal fluency and response inhibition. There is some indication that the semantic strategy component may account for the effects of verbal fluency, although evidence comes from one study and needs replication. Processing speed has been proposed as a substrate that may underlie the effects of executive dysfunction on treatment response. Although processing speed does not appear to account for the relationship between response inhibition and treatment outcome, this issue has yet to be assessed with respect to verbal fluency.

CONCLUSIONS

Verbal fluency and response inhibition are specific aspects of executive dysfunction that appear to impact antidepressant response rates. Disruption of the frontostriatal limbic circuit (particularly the anterior cingulate and dorsolateral prefrontal cortex) may explain the relation between these two mechanisms.

Change in cognitive functioning in depressed older adults following treatment with sertraline or nortriptyline

OBJECTIVE

The aim of this study was to compare the impact of nortriptyline to sertraline on change in cognitive functioning in depressed older adults.

METHODS

We used pre-post neuropsychological data collected as part of a 12-week medication trial comparing sertraline to nortriptyline in the treatment of older adults with non-psychotic, unipolar major depression to examine change in cognitive functioning. Neuropsychological assessments included mental status (Mini-Mental Status Exam), psychomotor speed (Purdue Pegboard), attention (Continuous Performance Test, Trail Making Test A), executive functioning (Stroop Color/word Test, Trail Making Test B), and memory (Buschke Selective Reminding Test).

RESULTS

Within treatment groups, patients treated with sertraline improved only on verbal learning. This change did not depend on responder status. Between treatment groups, patients treated with sertraline improved more in verbal learning compared with patients treated with nortriptyline. Looking at change in cognition as a function of medication condition and responder status revealed that sertraline responders improved more in verbal learning compared with nortriptyline responders but not more than sertraline non-responders or nortriptyline non-responders. Nortriptyline responders were the only treatment by responder status group to show no improvement in verbal learning from baseline to endpoint.

CONCLUSIONS

Unexpectedly, nortriptyline responders showed no improvement in verbal learning as compared with patients treated with sertraline or nortriptyline non-responders. However, given the small sample sizes and number of statistical tests (potential for type 1 error), replication is warranted.

MRI signal hyperintensities and failure to remit following antidepressant treatment

BACKGROUND

MRI signal hyperintensities predict poor remission to antidepressant treatment. Previous studies using volumetrics in outpatient samples have relied on total lesion volume. The purpose of this study was to test whether remission from geriatric depression depends on lesion volume by region of interest (ROI).

METHOD

Thirty-eight patients received baseline MRIs as part of a larger 12-week, randomized clinical trial comparing sertraline and nortriptyline in the treatment of late-life depression. MRIcro was used to quantify MRI-hyperintensity volume into total hyperintensity, deep white matter hyperintensity (DWMH), and periventricular hyperintensity (PVH) volumes. High versus low total, DWMH, and PVH volumes were defined based on the highest quartile of their respective distributions. Remission from depression was defined as a 24-item Hamilton Rating Scale for Depression score ≤ 7 for two consecutive weeks.

RESULTS

Patients classified as having high DWMH were 7.14 times more likely not to remit following antidepressant treatment compared to patients classified as having low DWMH (p=0.02). Similar odds ratios were obtained for PVH (OR=4.17, p=0.16) and total volumes (OR=5.00, p=0.05). Importantly, adjusting for age did not change the magnitude of these effects.

LIMITATIONS

A small and predominantly White sample.

CONCLUSIONS

This is the first study to test whether remission from geriatric depression depends on lesion volume by ROI in an outpatient sample. The pattern of remission rates and odds ratios was similar when patients were classified as having high DWMH, PVH or total volume suggesting that lesion location may not be critical.

MRI-defined vascular depression: a review of the construct

OBJECTIVE

To review the construct of MRI-defined vascular depression and to examine the substantive and methodological issues that bear on its validity as a distinct subtype of depression in late life.

DESIGN

Literature review.

RESULTS

We identified three areas that are critical to establishing the validity of MRI-defined vascular depression: (1) understanding and delineating the relationship between MRI hyperintensities, executive dysfunction, and antidepressant treatment outcome; (2) understanding the relationship between, and establishing the validity of, qualitative and quantitative approaches to the measurement of MRI hyperintensities (the primary feature of the proposed subtype); (3) establishing the clinical presentation and course of the subtype in the context of other late-life disorders.

CONCLUSIONS

Despite considerable data supporting the validity of MRI-defined vascular depression, there are a number of critical issues that remain, including establishing a causal relationship between cerebrovascular disease and late-life depression, establishing consistent diagnostic criteria, determining the importance of lesion type and location, and understanding the course of the disorder.