Eye Movement Desensitization Reprocessing (EMDR) therapy is an integrative psychotherapy approach that has been extensively researched and proven effective for the treatment of trauma. EMDR is a set of standardized protocols that incorporates elements from many different treatment approaches.
From the EMDR International Association website (© 1995-2018 EMDRIA EMDR International Association)
"No one knows how any form of psychotherapy works neurobiologically or in the brain. However, we do know that when a person is very upset, their brain cannot process information as it does ordinarily. One moment becomes "frozen in time," and remembering a trauma may feel as bad as going through it the first time because the images, sounds, smells, and feelings haven’t changed. Such memories have a lasting negative effect that interferes with the way a person sees the world and the way they relate to other people."
"EMDR seems to have a direct effect on the way that the brain processes information. Normal information processing is resumed, so following a successful EMDR session, a person no longer relives the images, sounds, and feelings when the event is brought to mind. You still remember what happened, but it is less upsetting. Many types of therapy have similar goals. However, EMDR appears to be similar to what occurs naturally during dreaming or REM (rapid eye movement) sleep. Therefore, EMDR can be thought of as a physiologically based therapy that helps a person see disturbing material in a new and less distressing way."
"One or more sessions are required for the therapist to understand the nature of the problem and to decide whether EMDR is an appropriate treatment. The therapist will also discuss EMDR more fully and provide an opportunity to answer questions about the method. Once therapist and client have agreed that EMDR is appropriate for a specific problem, the actual EMDR therapy may begin."
"A typical EMDR session lasts from 60 to 90 minutes. The type of problem, life circumstances, and the amount of previous trauma will determine how many treatment sessions are necessary. EMDR may be used within a standard "talking" therapy, as an adjunctive therapy with a separate therapist, or as a treatment all by itself."
Further info: What is EMDR?