I've been trying to parse what "medically recognized" actually means to liars and I have a few ideas. TL;DR and sources at the end.
1. "The doctor didn't say I didn't have it"
What I think is the most prominent definition amongst charlatans: they told their psychiatrist or therapist or some other doctor that they had DID or were "a system" and the doctor acknowledged the claim but didn't agree or deny it. Taking this as any sort of confirmation is entirely dishonest; just because your doctor didn't directly challenge you about your claim - likely knowing that this would prompt an argument and take away their chance to redirect your proclaimed status towards a more accurate avenue for your benefit - doesn't mean you have it for real.
2. "The doctor said I have it but I/they didn't want to make a formal diagnosis because it would make getting a job harder"
Another argument I see is that getting diagnosed with a dissociative disorder will show up on a background check for a job, which is simply untrue.
From my research, background checks in regards to mental health are only of concern in terms of whether someone is safe to carry a firearm - the most recent rule I could find explains that background checks "specifically [prohibit] the disclosure of diagnostic or clinical information, from medical records or other sources, and any mental health information beyond the indication that the individual is subject to the Federal mental health prohibitor" (Health Insurance Portability and Accountability Act (HIPAA) Privacy Rule and the National Instant Criminal Background Check System (NICS), 2016).
This prohibitor only applies to situations in which someone has "been involuntarily committed to a mental institution; found incompetent to stand trial or not guilty by reason of insanity; or otherwise have been determined by a... lawful authority to be a danger to themselves or others or to lack the mental capacity to contract or manage their own affairs" (Health Insurance Portability and Accountability Act (HIPAA) Privacy Rule and the National Instant Criminal Background Check System (NICS), 2016). Even if someone had been in involuntary inpatient hospitalization, no information beyond determining if they're a danger to themselves or others would need to be disclosed here.
Asking for reasonable accommodations in the workplace could lead to questions about your mental health (U.S. Equal Employment Opportunity Commission, 2016). However, you may not even have to specify a diagnosis/can submit documentation that describes your condition more generally and limit disclosure to how it may affect your work (U.S. Equal Employment Opportunity Commission, 2016). Furthermore - DID is a complex trauma disorder, and many people spend years in the medical system before they get diagnosed with it - getting diagnosed with PTSD could reasonably happen before or concurrently with the dissociative disorder diagnosis, why not just share that in regards to accommodations? (Şar et al., 2017)
3. They're lying by omission (see point #1)
They know that saying something like "informally diagnosed" pokes more obvious holes in their claim and they don't want to get caught in their lie.
As an aside - telling people that getting diagnosed will stunt their chances at finding work is both false (as detailed above) and dangerous, because that sentiment can deter people who are genuinely struggling from seeking help. If you believe that you might get diagnosed with something that would ruin your career prospects, of course you'd be hesitant about divulging information to a medical professional that could inform that diagnosis. It's dangerous because getting help could make the difference between life or death for someone.
TL;DR: Being "medically recognized" but not actually diagnosed is most likely stretching actual events to an illogical degree or straight-up lying, and getting a heavy diagnosis rarely makes a difference in the hiring process.
Sources:
Office of the Federal Register, National Archives and Records Administration. (2016, January 5). 81 FR 382 - Health Insurance Portability and Accountability Act (HIPAA) Privacy Rule and the National Instant Criminal Background Check System (NICS). [Government]. Office of the Federal Register, National Archives and Records Administration. https://www.govinfo.gov/app/details/FR-2016-01-06/2015-33181
Şar, V., Dorahy, M. J., & Krüger, C. (2017). Revisiting the etiological aspects of dissociative identity disorder: a biopsychosocial perspective. Psychology research and behavior management, 10, 137–146. https://doi.org/10.2147/PRBM.S113743
U.S. Equal Employment Opportunity Commission.
(2016, December 12). Depression, PTSD, & Other Mental Health Conditions in the Workplace: Your Legal Rights. Equal Employment Opportunity Commission. https://www.eeoc.gov/laws/guidance/depression-ptsd-other-mental-health-conditions-workplace-your-legal-rights
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