Methods and apparatuses for transdermal electrical stimulation. Described herein are single-use or limited-use TES apparatuses and methods of using them that include an integrated (e.g., flex-circuit) electrode assembly and controller apparatus including a waveform generator and power supply. Also described herein are TES apparatuses including a cord or wire having current control circuitry and configured to connect a mobile computing device (e.g., smartphone or wearable electronics) to an electrode assembly. Finally, also described herein are intermediate apparatuses including a flex-circuit electrode assembly including a waveform generator but receiving power from a cable connected to a mobile computing device.