Differential Diagnosis: What to Rule In and Rule Out

Accurate differential diagnosis is not merely a bureaucratic exercise. In the case of RSD, it is the difference between years of treatment that partially addresses symptoms and a clinical formulation that actually fits the person in your office.

Borderline Personality Disorder

Both involve intense emotional reactivity and significant fear of abandonment. The overlap is real, and comorbidity between BPD and ADHD is substantial — impulsivity and emotional dysregulation are features of both, and the presence of one significantly increases the likelihood of the other.12 The key differentiators: BPD involves chronic identity instability, idealization–devaluation cycles in relationships, and self-harm as a regulatory strategy more commonly than RSD does. RSD episodes tend to resolve within hours rather than days and are more specifically triggered by identifiable cues.

Bipolar II Disorder / Cyclothymia

RSD can look, at first presentation, like rapid cycling — the emotional storms are intense and shift quickly, sometimes with a euphoric flip side Dodson has called “rejection elation.” The key difference is trigger-specificity. Bipolar mood episodes arise relatively independently of environmental triggers and last days to weeks; RSD episodes are triggered, intense, and typically resolve within hours.

Social Anxiety Disorder

Both involve fear of negative evaluation, but the mechanism differs. Social anxiety is primarily anticipatory, cognitive, and organized around the fear of future evaluation. RSD is the acute, affective, nearly physiological pain response when rejection occurs. The person with SAD dreads the party; the person with RSD may enjoy the party and then lie awake for three hours convinced something they said was unforgivable.

Complex PTSD

ADHD and trauma co-occur at significant rates.13 The presence of ADHD does not rule out trauma; the presence of trauma does not rule out ADHD and RSD. These are frequently concurrent realities that require concurrent attention, and a careful trauma history is not optional.