II. Situating RSD Within the Clinical Landscape

Before the Mismatch Signature can be theorized fully, it is necessary to situate RSD within the broader clinical landscape it inhabits — and complicates.

2.1 RSD and ADHD: An Underacknowledged Core Feature

Despite decades of research into ADHD, the affective dimensions of the condition have received comparatively little systematic attention relative to its executive, attentional, and behavioral signatures. The DSM-5 does not list RSD among ADHD criteria, a point of ongoing controversy among clinicians working with adult ADHD populations (Barkley, 2015). Yet survey data from these populations consistently identify emotional sensitivity to rejection as among the most impairing features of their daily lives (Surman et al., 2013).

Russell Barkley’s influential extensions of ADHD theory have argued that emotional dysregulation — including rapid, intense emotional responding and difficulties in emotion regulation — should be considered a core feature of ADHD rather than a comorbidity (Barkley, 2010). Within this framework, RSD emerges not as a comorbid mood disorder but as a specific manifestation of impaired emotional regulation: the rejection-specific channel through which broader affective dysregulation expresses itself.

Thomas Brown’s cognitive model of ADHD similarly emphasizes the role of affective loading in ADHD — the way in which interest, challenge, novelty, urgency, and emotional significance modulate the activation of executive functions in ADHD brains in ways that differ substantially from neurotypical patterns (Brown, 2013). RSD, in Brown’s implicit framing, becomes comprehensible as the pathological attractor state that forms when the affective loading system is both hypersensitive and poorly regulated.

2.2 RSD Beyond ADHD: Borderline, Trauma, and Differential Considerations

RSD-like presentations appear in multiple diagnostic contexts, which creates significant clinical confusion. Borderline Personality Disorder (BPD) is characterized by intense fears of abandonment and extreme emotional responses to perceived rejection (American Psychiatric Association, 2013), which phenomenologically overlap substantially with RSD. Post-Traumatic Stress Disorder (PTSD) and Complex PTSD (Herman, 1992) similarly involve heightened reactivity to social threat cues, including rejection-adjacent stimuli. Social Anxiety Disorder involves pronounced distress around evaluation and rejection, though its affective profile differs in mechanism and structure from RSD.

The clinical challenge, then, is not identifying that a person is having an intense emotional response to something rejection-related — it is determining the structural logic of that response. This is precisely the diagnostic problem the Mismatch Signature is designed to address.