Gilomen SA, Lee CW (2015). The efficacy of acupoint stimulation in the treatment of psychological distress: A meta-analysis. J. Behav. Ther. & Exp. Psychiat. 48: 140-148.
This was a systematic review and meta-analysis including 18 Randomised Controlled Trials (RCTs), with a total of 921 participants. Twelve of the studies compared EFT with waitlist controls, 5 with minimal interventions and 1 with an alternative treatment. The authors report that EFT appears to produce an effect, producing a moderate effect size.
Most of the included studies were found to have several methodological shortcomings however, including lack of comparison of EFT to established treatments. The authors say this meant that it was not possible to determine if the effect is due to acupoint stimulation or to treatment elements that it has in common with other therapies, and therefore conclude that the evidence for EFT is yet to be established.
There is also an additional commentary here: http://www.efttappingtraining.com/eft-research-paper/efficacy-of-acupoint-stimulation-treatment-of-psychological-distress-meta-analysis/