SUD stands for Subjective Units of Disturbance (sometimes called Subjective Units of Distress). It’s a simple 0-to-10 scale that measures how much emotional distress you feel when you think about a traumatic memory. In EMDR therapy, your therapist uses this number to track whether processing is working and to decide when it’s safe to move to the next stage of treatment.
How the SUD Scale Works
The scale runs from 0 to 10. A score of 0 means no disturbance at all, completely neutral. A score of 10 means the highest level of distress you can imagine. During a session, your therapist will ask you a specific question: “On a scale of 0 to 10, where 0 is no disturbance or neutral and 10 is the highest disturbance you can imagine, how disturbing does it feel to you now?”
There’s no right or wrong answer. The number is entirely subjective, based on what you feel in the moment, not what you think you should feel. Two people processing similar traumatic events might rate their distress very differently, and that’s expected. The value of the SUD isn’t in comparing one person to another. It’s in tracking how your own number changes over the course of a session.
The scale wasn’t invented for EMDR. Joseph Wolpe and Arnold Lazarus introduced it in 1966 as a tool for behavior therapy, particularly exposure-based treatments. Wolpe used the term “sud” to describe a single unit of disturbance. When Francine Shapiro developed EMDR, she adopted the scale because it gave therapists a quick, reliable way to check in with clients during memory processing without pulling them too far out of the experience.
Where SUD Fits in the Eight Phases of EMDR
EMDR therapy follows eight structured phases, and the SUD score plays its biggest role in two of them.
In Phase 3 (Assessment), your therapist asks you to bring up the target memory, notice the emotions and body sensations that come with it, and rate your distress level. This baseline SUD score establishes where you’re starting. If you rate a childhood memory at a 7, for example, that number becomes the benchmark for measuring progress.
In Phase 4 (Desensitization), the actual processing begins. You focus on the traumatic memory while following side-to-side eye movements, sounds, or taps. After each set of bilateral stimulation, your therapist checks in and asks for a new SUD rating. The goal is for your distress to drop steadily. Processing continues until the SUD reduces to 0, or to 1 if that’s the lowest level that feels realistic for your situation. Only when desensitization is complete does your therapist move on to Phase 5, where you work on strengthening a positive belief about yourself.
SUD and VOC: Two Scales That Work Together
EMDR uses a second scale alongside SUD called the Validity of Cognition (VOC). While SUD measures negative distress, VOC measures how true a positive belief feels. It runs from 1 (the belief feels completely false) to 7 (it feels completely true).
Here’s how they connect: at the start of processing, you might hold a belief like “I am safe now” but rate it a 2 on the VOC because it doesn’t feel true at all. Your SUD for the traumatic memory might be an 8. As processing works, the SUD drops and the VOC rises. Research has confirmed this relationship directly: reductions in SUD scores predict increases in VOC scores, and improvements in both are linked to decreases in tension, depression, anger, and fatigue.
Think of SUD as measuring how much the old wound still hurts, and VOC as measuring how much a healthier perspective has taken hold. Successful EMDR moves both numbers in the right direction.
What Happens When the SUD Doesn’t Drop
Sometimes your SUD score plateaus or stays stubbornly high during a session. This doesn’t mean EMDR isn’t working for you or that something is wrong. It means the therapist needs to adjust their approach.
One common reason for a stalled SUD is that the memory being processed connects to an earlier, deeper memory that hasn’t been addressed yet. Your therapist may shift focus to identify and target that earlier experience. Another possibility is dissociation, where your mind pulls away from the memory as a protective response rather than fully engaging with it. This can look like going blank, feeling numb, or giving a SUD rating that doesn’t match your visible emotional state.
Therapists have several tools for these situations. They might use cognitive interweaves, which are brief, targeted questions or statements designed to get processing moving again. They can also adjust the intensity of the bilateral stimulation. Research on EMDR outcomes has found that clients who respond to processing by mentally “distancing” from the memory (recognizing it as something that happened in the past rather than reliving it in the present) tend to show greater symptom improvement than those who stay immersed in the trauma material. Interestingly, factors like age, gender, and baseline severity of PTSD symptoms don’t predict how quickly SUD scores drop, which means a high starting number doesn’t indicate a harder road.
What Your SUD Score Tells You
Your SUD rating is a snapshot of your nervous system’s reaction to a memory at a specific moment. It captures the gut-level emotional charge, not your intellectual understanding of the event. You might know logically that a car accident ten years ago is over, but if picturing it sends your heart racing and tightens your chest, your SUD will reflect that.
Over the course of successful EMDR treatment, you’ll likely notice that memories which once registered as a 7 or 8 settle to a 0 or 1. The memory doesn’t disappear. You can still recall what happened in detail. But the emotional intensity attached to it fades, and it starts to feel like something that happened rather than something that’s still happening. That shift from high SUD to low SUD is one of the clearest markers that traumatic material has been fully processed.
If you’re preparing for your first EMDR session, knowing about the SUD scale ahead of time can make the process feel less mysterious. You’ll be asked for a number repeatedly, and the simple act of assigning a number to your feelings can itself be grounding. It gives you and your therapist a shared language for something that otherwise lives entirely inside your experience.