Carly Simon swears by it. The daytime show “The Doctors” gave it a glowing review. Ads for it seem to be invading psychiatrists’ Google search results. We’re talking, of course, about the Fisher Wallace Stimulator, touted by the manufacturer as being an effective treatment for depression, anxiety, insomnia, and pain (Fisher Wallace website). The Alpha-Stim device makes similar claims (Alpha-Stim website). How do these devices work? Are they actually effective? And where do they fit into the rapidly expanding array of neuromodulators?

If you want to understand these devices, it’s best to start by learning about their simpler cousin process, transcranial direct current stimulation (tDCS). Picture a battery with a wire attached to the negative end (the anode) going into a light bulb and returning to the battery’s positive end (the cathode). Electrons flow through the wire, heating the lightbulb’s filament to create light. This one-way electrical circuit is called direct current (DC).

Now, imagine that the lightbulb is replaced with your skull, and the wires from the battery go to conductive pads that are kept on either temple by a headband. You are now picturing a simple tDCS device. A small charge will flow to your temple and will stimulate the part of your cortex under the electrode. If we’re talking about, say, the left dorsolateral prefrontal cortex, which is thought to be hypoactive in depression, this stimulation will theoretically increase electrical activity there and ease your depression.

It makes sense, and it may actually work—according to a recently published randomized sham-controlled trial. In the study, 120 mildly treatment-resistant patients with MDD were randomized to tDCS alone, tDCS combined with sertraline, sertraline alone, or placebo, and followed for 6 weeks. Both tDCS and combined tDCS and sertraline worked better than placebo alone or sertraline alone, and the combined treatment posted the best outcomes of all (Brunoni AR et al, JAMA Psychiatry 2013;70(4):383–391). It’s not a huge study, and we’d like more data, but we can at least say that this technology looks promising—and the side effects are almost non-existent.

How are the Fisher Wallace Stimulator and the Alpha-Stim devices related to tDCS? They’re very similar except that the current going to the skull is alternating current (AC) instead of direct current (DC), and for that reason they are categorized as tACS (transcranial alternating current stimulators). In DC, the flow of electrons is constant and in one direction, but in AC, the flow changes direction frequently. AC is how electricity is transported to households, and in that context it has the advantage of being more efficient and cheaper to deliver.

Why would AC have any advantage over DC for brain stimulation? It’s not clear. The theoretical advantage of AC is that the brain has its own natural oscillations, and with alternating current you can either try to match the brain’s ongoing frequency by stimulating at that frequency, or disrupt it with alternate frequencies. Both the FWS and Alpha-Stim have patented frequencies (sometimes called “waveforms”), which the manufacturers say are the keys to how their devices modulate neuronal activity.

Regardless of the theoretical mechanism, the key issue is whether the contraptions actually help your patients. The company websites make prominent mention of the fact that their devices have been “cleared” by the FDA for depression and other conditions. But for those not steeped in FDA regulatory policy, this is a potentially misleading statement. the FDA “clears” a device, it does not mean that it has been “approved,” nor does it mean that the agency has reviewed any efficacy data. Instead, it means that the FDA has determined that the device is similar to other devices previously approved, often for indications completely different from the one being marketed. Nonetheless, the company websites state that the devices are proven to be effective treatments for depression.

To dig deeper into these claims, we reviewed both the company-cited publications and any other data we could find via standard databases such as PubMed. We were not able to find any published large-scale (meaning 200-400 subjects) randomized, controlled trials for the treatment of MDD. The data that both companies cite as demonstrating efficacy are derived from small studies (none have enrolled more than 70 patients, and most enrolled about 20) focusing on other conditions (such as substance use and anxiety disorders) or on mixed pathologies. Some of these studies included a depression measure, but none specifically targeted MDD. The company websites also cite anecdotal evidence from clinicians. However, none of these sources of evidence, either alone or in aggregate, rise to the level that we usually require when deciding on treatments for our patients. At best, they suggest possible efficacy.
What about tDCS? The evidence for tDCS in depression is stronger (we referenced an impressive result above), although smaller studies have been contradictory. No tDCS device has yet been FDA cleared for any psychiatric indication, though patients can buy such devices very cheaply from the internet.

The bottom line is that both tACS and tDCS devices suffer from a shortage of good evidence for efficacy in depression. While we did not thoroughly review the evidence for other indications, such as anxiety or insomnia, it appears that the company-cited studies for these are also quite small and methodologically weak.

TCPR Verdict: Fisher Wallace and Alpha-Stim for depression: They probably can’t hurt, but they may not help either.