The goal of this clinical trial is to investigate the effectiveness of Eye Movement Desensitization and Reprocessing (EMDR) therapy in reducing pain intensity in individuals with chronic painful diabetic neuropathy (PDN). The main questions it aims to answer are:

1. Does EMDR therapy significantly reduce pain intensity in individuals with chronic PDN?
2. What is the impact of EMDR therapy on secondary outcomes, specifically anxiety, sleep disturbances, and personalized pain-related limitations? Additionally, the study will explore the correlation between pain scores and symptoms of post-traumatic stress disorder (PTSD) in individuals with chronic PDN.

Participants will undergo EMDR therapy sessions, focusing on the processing of emotionally charged pain-related events and addressing the pain itself. Main tasks for participants include active engagement in EMDR therapy sessions. Treatment outcomes, including changes in pain intensity, anxiety levels, sleep quality, and personalized pain-related limitations, will be monitored throughout the study.

The study adopts a single-case experimental design, replicated nine times (N-of-1 study).

Research on the effectiveness of EMDR therapy for neuropathic pain is limited to studies on phantom pain (and complex regional pain syndrome (CRPS). In the case of CRPS, two case reports are available, and for phantom pain, there is one RCT with 60 participants and three studies with 10 or fewer participants, without a control group. In the phantom pain studies, EMDR therapy focused on processing memories of events leading to the onset and exacerbation of pain (initial injury, amputation) and pain-related memories with current emotional charge. Sometimes, but not always, these events were life-threatening, as seen in PTSD (American Psychiatric Association Painful experiences, such as falling on the stump, or anticipated catastrophes (nightmares or disaster fantasies) with current emotional charge, were also processed. In the CRPS studies, EMDR therapy targeted traumatic events, including those from childhood, and pain-related events. In all studies, after the events were processed, pain itself was taken as the target for EMDR therapy. The studies demonstrate that after EMDR therapy, pain intensity decreases, as do comorbid symptoms.

Research on the effectiveness of EMDR therapy as a treatment for chronic PDN, to the best of our knowledge, has not been conducted. The aim of the presented study is to investigate the effect of EMDR therapy on chronic PDN.

Inclusion criteria:

• Age: ≥ 18 years.
• Diagnosis of Diabetes Mellitus.
• Severity of pain in the past month, NRS-pain score ≥ 6.
• Ability to communicate in both written and spoken Dutch.
• Willingness to participate in the study (signed informed consent (IC)).

Exclusion criteria:

• Severe psychiatric disorders requiring immediate treatment.
• IQ < 80.
• Initiation of medication within 3 months before the start of the study (medication in use for more than 3 months can be maintained; discontinuation of medication during the study is possible but not desirable).
• Concurrent psychotherapeutic treatment targeting neuropathic pain during the study.
• Substance abuse and/or dependence, unless medically prescribed.
• Inability to complete the questionnaires.
• Co-morbid conditions affecting the lower extremities, such as peripheral arterial disease, severe rheumatoid arthritis, osteoarthritis. Other conditions causing pain in the feet and/or damage to the peripheral nervous system, for example, ulcers.
• Co-morbid chronic pain syndromes.

In psychological research, it is not feasible to employ a 'blind' approach for both participants and EMDR therapists regarding the intervention. An independent research assistant, not otherwise involved in the study, oversees the completion of daily measurements and questionnaires. This ensures that EMDR therapists remain blind to the obtained data. An exception to this is the utilization of the results from the LEC and PCL-5, which are employed for case conceptualization. There will be no randomization of baseline length or initiation of the intervention, as seen in multiple baseline designs.