Abstract
Identical (monozygotic) twins represent a unique “natural experiment” for isolating the role of temperamental differences in psychotherapy processes, and controlling for genetic and environmental variables. This research presents a comparative case study of 20 sessions of Schema Therapy (ST) with 19-year-old twin sisters, both diagnosed with severe Social Anxiety Disorder and core schemas in the Disconnection and Rejection domain, specifically Defectiveness/Shame. Despite sharing an identical genetic background and a similar trauma history (adolescent illness and peer bullies), the clients exhibited distinct differences in temperament and ego strength. Client A (characterized by a “difficult” temperament and high emotional inhibition) displayed significant resistance to change, dominated by a rigid Punitive Parent mode. In contrast, Client B (characterized by an “easy” temperament and higher resilience) demonstrated rapid engagement with cognitive and experiential interventions. Results indicated that while both clients experienced significant symptom relief, their therapeutic trajectories diverged: whereas Client B successfully established an independent identity, Client A required a more intensive focus on Limited Reparenting to overcome emotional blockages. This study demonstrates that even when schema profiles are identical, temperament functions as a critical moderator, necessitating the tailoring of therapeutic strategies, specifically the balance between cognitive and experiential techniques, to the individual’s temperamental capacity.
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