In the active stimulation condition a constant current of 2mA intensity was applied for 30 minutes with a 5-second ramp phase at the beginning. In the sham stimulation condition the machine was activated for 30 seconds using identical parameters but was then switched off without the patient's knowledge. This sham control is commonly employed because over the initial 30 seconds of stimulation, an initial sensation of tingling under the electrode fades away. Patients are less likely to distinguish active from sham conditions if the initial period of tingling is present in both.