Clinical Practice
EMDR Phase 4: Desensitization
Phase 4 is where bilateral stimulation drives desensitization of the target memory. Learn what happens step-by-step and how to run Phase 4 online.
BilateralSync · Updated · 8 min read
Overview
Phase 4 is the desensitization phase of EMDR. The client holds the target image, negative cognition and associated body sensation in mind while the therapist delivers sets of bilateral stimulation. Between sets, the therapist checks in briefly and follows the client's associative chain until the Subjective Units of Disturbance (SUD) score approaches zero.
What the evidence says
Phase 4 is the phase most directly studied in dismantling research. The procedural specificity — target activation, dual-attention BLS, brief check-ins, following associations — is what distinguishes EMDR from simple exposure or free association. The protocol itself is defined in the EMDR literature and training (Shapiro, 2018; Leeds, 2016), not by any software tool.
In practice
Practical Phase 4 skills include: pacing sets long enough for meaningful processing but not so long that the client loses dual attention; using minimal prompts such as 'notice that' and 'go with that'; using cognitive interweaves when processing loops; and monitoring the window of tolerance. These are clinical skills taught in EMDR training.
Remote delivery: technical considerations (separate from the protocol)
The section above describes the EMDR protocol. This section covers only the technical side of running Phase 4 remotely. Nothing here changes the protocol, and BilateralSync does not define clinical procedure.
- Control: the therapist needs to start, stop and adjust stimulation instantly. In a browser-based tool such as BilateralSync this happens from the therapist's screen, while the therapist stays on video for check-ins.
- Visibility: keep the client's face visible on video during sets so you can observe signs of distress or loss of dual attention.
- Audio: if tones are used, confirm headphone alternation before the first set.
- Interruptions: agree in advance what happens if the connection drops mid-set (see remote closure and grounding).
- Timing: allow enough time to stop desensitization and move to closure before the session ends.
Setup steps are in how to set up an online EMDR session; research on set length is in BLS speed and set length.
Frequently asked questions
- How long is a typical Phase 4 set?
- Protocol texts describe a starting point of around 24 back-and-forth movements, adjusted according to the client's response. No single optimal set length has been established by research.
- What is a SUD score?
- Subjective Units of Disturbance — a 0–10 scale the client uses to rate current disturbance associated with the target memory.
- Can Phase 4 be done online?
- Many clinicians conduct Phase 4 remotely, and early studies of online EMDR are encouraging. Whether it is appropriate for an individual client is a clinical decision.
References
- Shapiro, F. (2018). Eye Movement Desensitization and Reprocessing (EMDR) Therapy, 3rd ed. Guilford Press.
- Leeds, A. M. (2016). A Guide to the Standard EMDR Therapy Protocols for Clinicians, Supervisors, and Consultants, 2nd ed. Springer.
- Lenferink, L. I. M., Meyerbröker, K., & Boelen, P. A. (2020). PTSD treatment in times of COVID-19: A systematic review of the effects of online EMDR. Psychiatry Research, 293, 113438.
This article is general professional information for clinicians. It is not clinical advice and does not replace EMDR training, consultation or individual clinical judgment. BilateralSync is a tool for delivering bilateral stimulation; it is not a treatment or a medical device.