Pre-treatment letter fluency performance predicts antidepressant response to transcranial direct current stimulation.

Journal of affective disorders

PubMedID: 27288957

Martin DM, Yeung K, Loo CK. Pre-treatment letter fluency performance predicts antidepressant response to transcranial direct current stimulation. J Affect Disord. 2016;203130-135.
BACKGROUND
Transcranial direct current stimulation (tDCS) is a promising new treatment for depression, however, clinical trials to-date indicate variable efficacy, thereby raising the need to identify inter-individual predictors of response. In the current study we aimed to investigate pre-treatment neurocognitive performance as a predictor of antidepressant response to tDCS.

METHODS
Data was pooled from five clinical trials, including two randomised controlled trials (RCTs), which investigated the antidepressant effects of anodal tDCS administered to the prefrontal cortex. Data from 57 patients were included in the analysis. Mood was assessed before and after an acute course of treatment using the Montgomery-├ůsberg Depression Rating Scale. The following neurocognitive tests were administered prior to treatment: Simple and choice reaction time, the Symbol Digit Modalities Test (SDMT), Rey Auditory Verbal Memory Task (RAVLT), Digit Span, and the Controlled Oral Word Association Test (COWAT).

RESULTS
Better pre-treatment letter fluency performance measured using the COWAT predicted antidepressant response to tDCS after controlling for confounds.

LIMITATIONS
Small sample size and analysis included data from both RCTs and open label studies.

CONCLUSION
Pre-treatment letter fluency performance, an ability subserved by the left prefrontal cortex, the primary site of stimulation, is a predictor of response for tDCS treatment for depression. This study highlights the importance of inter-individual neurobiological differences in mediating tDCS antidepressant effects.