Is it possible to predict the long-term response to venlafaxine with the use of biological markers and psychophysiological methods?

No differences between drug naive and drug experienced unipolar depressed patients in terms of neurobiological testing: a cross sectional study

Successful antidepressant treatment has been associated with concomitant changes in brain function, consolidated as long as treatment is continued and remission is preserved. The present study aimed at assessing the impact of prior antidepressant treatment on brain function in currently depressed but unmedicated individuals by investigating for any differences between antidepressant-naïve vs. antidepressant-experienced subjects. Fifty right-handed patients (22 medication-naïve vs. 28 medication-experienced), suffering from major depression participated in the study. They all underwent a standardised clinical interview and psychometric assessment combined with neurobiological tests (brain SPECT, Dexamethasone Suppression Test, Dexfenfluramine Challenge Test, electro-oculogram, flash-electroretinogram and flash-visual evoked potentials and pattern-reversal visual evoked potentials). No significant differences between medication-naïve and medication-experienced depressed subjects were found in terms of the neurobiological markers assessed, after controlling for age, sex, age at onset, number of depressive episodes, depression subtype (melancholic, atypical or undifferentiated) and severity of current episode. Unmedicated currently depressed patients, no matter their previous exposure to antidepressants, show similar changes in brain function. This does not necessarily mean that antidepressants do not have a long term effect on brain physiology, since not all patients relapse. However, it seems that those patients who relapse after stopping medication, seem to 'regress' to an 'as if never medicated' state, with regard to brain function. These findings might suggest that continuous maintenance treatment with antidepressants is essential for patients at high risk to relapse. Alternatively, they might suggest that our methodology assesses only a shallow and mainly state part of the pathophysiology of depression.

Electroretinographic assessment in major depressed patients receiving duloxetine: might differences between responders and non-responders indicate a differential biological background?

INTRODUCTION

Despite intense research efforts, still too little is known about the biological determinants of depression, thus soliciting diverse study approaches. Among others, the electroretinography (ERG) has been proposed even as a putative proxy (retinal) measurement of central dopaminergic activity for Major Depressive Disorder (MDD) both in drug-naïve patients and subjects receiving antidepressant treatments. Nonetheless, current evidences are merely preliminary, essentially considering just older classes of antidepressants, thus requiring confirmation studies even with newer agents as duloxetine.

METHOD

Twenty MDD subjects and 20 matched controls received duloxetine 60 mg/day for 12 weeks, being monitored both by standard ERG recording and by administration of the Hamilton scales for Depression and Anxiety and the Young Mania Rating Scale at baseline and week 12 (end of the study).

RESULTS

ERG mean rod b-wave amplitude significantly reduced from baseline to week 12 in those depressed subjects achieving final response (p=.024), decreasing from the highest rank values to the ones, substantially unmodified, seen among non-responders and controls.

LIMITATIONS

Small sample size and lack of multiple assessments.

CONCLUSIONS

At least some MDD patients responding to duloxetine might exhibit a peculiar ERG pattern, hypothetically indicating a specific biological background. If confirmed by larger-sampled studies, these results might shed further light in the understanding of the biological determinants of different subtypes of depression, ideally showing alternative patterns of response upon different treatment interventions.