Brief reportContinuation transcranial direct current stimulation for the prevention of relapse in major depression
Introduction
Transcranial direct current stimulation (tDCS) is emerging as a promising treatment for depression and other neuropsychiatric disorders (Arul-Anandam and Loo, 2009, Kalu et al., 2012, Nitsche et al., 2009). tDCS is a neurostimulation technique involving a weak, unidirectional and hence polarising electrical current, delivered to the brain via rubber electrodes placed on the scalp. Relative to other brain stimulation techniques, tDCS has several advantages, including cost effectiveness and minimal adverse effects (Nitsche et al., 2008). These factors support its potential for clinical translation as a treatment, once efficacy and safety are confirmed in research trials (Brunoni et al., 2011a, Nitsche et al., 2008).
Earlier tDCS depression trials in the 1960s and 1970s used relatively low stimulus parameters, with electrode montages that likely further attenuated the effective stimulation intensity (Moliadze et al., 2010), and widely ranging methodology in terms of stimulation approach and equipment, resulting in efficacy outcomes that were inconsistent between studies and overall inconclusive (Arul-Anandam and Loo, 2009). The development of modern stimulation equipment enabling reliable delivery of tDCS at higher stimulus parameters has led to recent controlled clinical and pilot trials with more promising results (Boggio et al., 2008, Brunoni et al., 2011b, Bueno et al., 2011, Fregni et al., 2006, Kalu et al., 2012, Loo et al., 2012, Loo et al., 2010, Palm et al., 2009). Recently, in the largest sham-controlled clinical trial conducted to-date (Loo et al., 2012), we showed that 2mA tDCS, applied for 20 min each weekday for 3 weeks, had significantly greater antidepressant effects than sham stimulation. Little, however, is known about the duration of these effects following an acute course of treatment, which usually consists of tDCS given daily or every second day over 1–6 weeks. Previous sham-controlled studies have only reported outcomes up to one month following acute treatment (Boggio et al., 2007; Loo et al., 2012, Loo et al., 2010). Should the efficacy of tDCS in treating an episode of depression be confirmed, it is important to determine whether a continuation or maintenance stimulation protocol would be useful for preventing relapse.
In this prospective study we examined relapse rates in participants who had open label tDCS treatments in a continuation treatment schedule for up to 6 months following clinical response to an acute treatment course of tDCS.
Section snippets
Participants
The clinical and demographic characteristics of the 26 participants are presented in Table 1. Four of these participants received two different courses of continuation tDCS, each one following a separate acute course of tDCS. Thus, the final analysis included 30 courses of continuation tDCS. All four participants who had completed two acute courses were involved in a sham-controlled clinical trial (Study 1), and then an open label pilot study (Study 2), as previously described (Martin et al.,
Patient and treatment characteristics
The mean age of participants was 47.2 (SD=14.0) years, 15 were female, 21 had melancholic depression and three had bipolar II depression. The treatment and clinical data of the 26 participants across the two studies are presented in Table 1. There were no significant differences in these treatment and clinical variables between studies.
Risk factors and survival analysis
Higher number of adequate courses of antidepressant medications failed in the current episode was the only variable significantly related to relapse (Hazard
Discussion
This is the first study to examine the use of continuation tDCS treatment to prevent relapse following response to an acute course of tDCS. Continuation treatment was well tolerated and majority of participants reported no side-effects other than sensations under the electrodes during both weekly and fortnightly tDCS treatment.
Continuation tDCS, given weekly for the first 3 months, resulted in the majority of responders remaining well, though the relapse rate increased after treatments were
Role of funding source
This study was supported by an Australian National Health and Medical Research Council (NHMRC) Project Grant no. 510142. The NHMRC had no further role in study design, in the collection, analysis and interpretation of data, in the writing of the report, and in the decision to submit the paper for publication.
Conflict of interest
No conflict declared.
Acknowledgements
The authors would like to acknowledge Vincent Chan for his work on this study.
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