Final fusion is when someone with dissociative identity disorder shifts from having multiple selves to having one single unified self . Essentially, it is a treatment process where they become one person.
Dissociative identity disorder (DID) is characterized when an individual has multiple different identity states, usually referred to as “alters”. When these separate identities combine into one new and single self, that would be the process of final fusion.
It is considered a treatment path, though it is not the only treatment path for DID—as it is not always desirable or possible to achieve for every system*. The other alternative is cooperation between all identities , which is known by the DID community and some professionals as “functional multiplicity” or “resolution” [2,4].
*Note: A system (or “system of identities”) is the typical term used to describe an individual with multiple identity states, i.e. someone with dissociative identity disorder is a “system.”
How is Final Fusion Achieved?
There is an underwhelming amount of research on the process of fusion. What research is out there is sometimes considered unethical or dismissive of the actual needs and experiences of the dissociative identity disorder community.
That being said, the protocol the ISSTD shares includes three beneficial and broad stages for recovery from dissociative identity disorder, which can lead to fusion.
- Establishing safety, stabilization, and symptom reduction
- Confronting, working through, and integrating traumatic memories
- Identity integration and rehabilitation. 
As someone who has gone through the process of final fusion, I found that my therapeutic journey did involve a path along these three stages, although it wasn’t intentional by my providers.
The stabilization of dissociative symptoms and comorbidities came before any traumatic memory processing occurred. Following that, all individual alters began processing their trauma memories, mainly through talk therapy. Finally, we began sharing memories amongst each other. This seemed to reduce the need for dissociative amnesia between alters and eventually lead to a natural complete fusion.
Barriers to Reaching Final Fusion
It is generally considered a lengthy process to treat dissociative identity disorder, usually involving many years of trauma recovery work alongside the three stages listed above. In some cases, final fusion cannot be achieved. The ISSTD lists multiple barriers to achieving final fusion, including:
- chronic and serious situational stress
- avoidance of unresolved, extremely painful life issues, including traumatic memories
- lack of financial resources for treatment
- comorbid medical disorders
- advanced age
- significant unremitting DSM comorbidities
- significant investment in alters or DID 
Noting the last point, many people in the dissociative identity disorder community have shared strong connections across alters. Friendly relationships can form between different alters, leading to a system wanting to build stronger connections and not “fuse them away.”
Collaboration between alters is also considered a valid treatment path. Not all systems may choose the path of final fusion. This needs to be respected by professionals, and the pathologizing of functional multiplicity as “deviant” or “wrong” needs to end. A large portion of the DID community does not seek fusion and continues to function well even while multiple . The goal is always to move the DID system towards more integrated functioning, which can include collaboration between alters .
Prognosis of Final Fusion
Several studies have indicated final fusion has been achieved in 16.7-33% of people with DID , meaning it is not the majority outcome for the entire DID community. Despite being labeled as the most stable treatment for dissociative identity disorder, many systems will self-report their final fusion disappearing and fragmentation of identity reoccurring.
Personally, I experienced the dissolution of my own state of fusion, about 14 months after fusing. My experiences matched many others in the community: high stress, new traumas, and increased comorbid symptoms made it difficult to remain fused.
Increased comorbidities due to final fusion have been noted in various texts, as well. People who have undergone final fusion may remain suicidal, experience unstable moods, or other disruptions to functioning even after this treatment path .
Additionally, final fusion can come with a feeling of subjective loss . Alters have relationships with one another and can often feel, to the person with DID, as separate individual people living within one shared body. Because of this, final fusion is not always desired. Any forced fusion, or unwanted fusion, may have a chance of dissolving as well.
All in all, final fusion is a treatment phenomenon that must be made with consent and vivid engagement of the system being treated. The practitioner should also inform their client of the potential risks and challenges while embarking on a journey towards final fusion.
To Learn More About Dissociative Identity Disorder
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 International Society for the Study of Trauma and Dissociation (2011): Guidelines for Treating Dissociative Identity Disorder in Adults, Third Revision, Journal of Trauma & Dissociation, 12:2, 133-187
 Clayton, K. (2005). Critiquing the Requirement of Oneness over Multiplicity: An Examination of Dissociative Identity (Disorder) in Five Clinical Texts. E-Journal of Applied Psychology, 1(2), 9–19. https://doi.org/10.7790/ejap.v1i2.21
 Ross, C. A. (1989). Multiple Personality Disorder:Diagnosis, Clinical Features, and Treatment. Canada: John Wiley & Sons, Inc.
 Manning, Elise A., “The ambiguous loss of post-integration : a theoretical analysis of the effects of integration on clients with dissociative identity disorder” (2013). Masters Thesis, Smith College, Northampton, MA.
As always, lived experience and community outreach is included in these blogs, as well.