1Sezione di Psichiatria Dipartimento di Medicina Università di Perugia, Didatta LIRPA Roma
Keywords: sibling complex; twinship; obesity; body; individuation.
Abstract: Despite the extensive literature on the biological, psychological, and social determinants of obesity, the role of early relational configurations in the development of bodily symptoms remains only partially explored. In particular, the sibling bond—and more specifically monozygotic twinship—has rarely been investigated as a shared matrix of psychic organization expressed through the body. Prevailing models tend to privilege an individual perspective, overlooking the possibility that bodily symptoms may serve a co-constructed function within highly symmetrical relational systems. From a psychodynamic perspective, the body may be understood as a symbolic site in which relational patterns, affective configurations, and difficulties in differentiation find expression..
In this sense, twinship represents a paradigmatic context for observing difficulties in the individuation process and the persistence of shared narcissistic configurations.
This paper explores these dynamics through the clinical analysis of a case involving monozygotic
twin sisters with severe obesity, highlighting the symptom as an expression of dual identity and as a defensive attempt to preserve an original state of unity.
INTRODUCTION
Despite the vast scientific literature devoted to obesity and eating disorders, the role of sibling dynamics—and, even more radically, twinship—in the genesis and organization of bodily symptoms remains insufficiently explored. Within psychodynamic models, this relational dimension continues to receive limited attention, as if the symptomatic body were conceived primarily in individual terms rather than as the inscription of a shared psychic narrative.
In contemporary clinical thought, interest in sibling relationships has progressively re-emerged as an indispensable axis alongside, rather than in opposition to, the Oedipal complex. Twinship offers a privileged framework for observing the most archaic and persistent forms of sibling attachment, in which the process of individuation may be hindered by an original experience of fusion.
In such cases, the body often assumes a central role—not only as a symptomatic surface, but also as a shared psychic space where fantasies, identifications, and defenses are deposited. From this perspective, obesity may represent a concrete inscription of the bond, a “shared substance” that maintains unity where symbolic separation remains difficult.
THE SIBLING COMPLEX AND THE BODY
The sibling complex encompasses the unconscious representations, narcissistic investments,
and ambivalent dynamics structured around the presence of another similar individual belonging to the same generation. Unlike the Oedipal complex, it involves the alterity of the “almost-equal,” the double, bringing into play rivalry, identification, alliances, and fantasies of fusion. In twinship, these dynamics become intensified: the sibling is not merely another person,
but a mirror-like figure who may function as an extension of the Self. The danger is that separation may be experienced as an intolerable loss,a rupture, or even the annihilation of primary unity. Within this framework, the body may become a concrete substitute for psychic boundaries: a “thickened” limit that is paradoxically shared, attempting to preserve narcissistic continuity where subjective differentiation struggles to emerge.
CLINICAL CASE
Enrica and Carla are 45-year-old monozygotic twin sisters. They entered clinical observation at different times, yet with remarkably similar complaints: difficulty controlling weight, depressive experiences, feelings of emptiness, and repeated failures in achieving emotional autonomy.
Both presented with severe obesity that developed progressively during adulthood.
Their personal histories were deeply intertwined: apart from their occupations, they shared educational experiences, friendships, and many life choices.
Neither established a stable romantic relationship, and both described brief affective relationships that ended when greater differentiation from the sister became necessary.
Psychodiagnostic assessment included clinical interviews and standardized instruments:
– SCID-5-SPQ -PD (Structured Clinical Interview for DSM-5 – Screening Personality Questionnaire)
– SCID-5-CV ( Structured Clinical Interview for DSM-5 Clinical Version)
– Eating Disorder Inventory-3 (EDI-3)
– Body Shape Questionnaire (BSQ)
– Binge Eating Scale (BES)
– CORE-OM (Clinical Outcomes in Routine Evaluation – Outcome Measure)
First Twin
Enrica, a 45-year-old woman, presented for clinical evaluation with severe obesity (BMI = 56.01), falling within the range of class III obesity. Her explicit request focused on weight loss; however, it was articulated in a markedly passive manner, as though entrusted to an external transformative force, suggesting a quasi-magical expectation of change. From the earliest interviews, it became evident that this request was accompanied by an implicit need to preserve a fragile sense of inner cohesion and to avoid the risk of fragmentation of the Self. Her weight history revealed a fluctuating course, with an initial significant increase during early adulthood and a progressive escalation in recent years leading to her current weight. The onset of binge-eating episodes was reported around the age of 28, becoming more consistently established from the age of 30 onward. During periods of greater severity, binge-eating episodes occurred frequently on a weekly basis and were characterized by loss of control, intense psychological distress, and, simultaneously, an immediate sense of gratification. Over time, food—together with promiscuous relational and sexual behaviors—appeared to acquire a regulatory function with respect to internal states of tension and affective disorganization. At clinical observation, the patient presented with a monochromatic appearance, predominantly dressed in black, displaying hypomimic facial expression and a pervasive sense of suffering. Eye contact was intermittent and at times avoidant, becoming more stable only during moments of heightened emotional engagement. Psychomotor activity appeared slowed, while consciousness remained alert but characterized by attentional fluctuations when emotionally salient themes emerged. Speech was generally coherent and appropriate, although occasionally interrupted by the emergence of intense affective experiences. From the perspective of psychological functioning, impairments testing, low frustration tolerance, and marked impulsivity were observed, together with poorly defined ego boundaries. Predominant defensive mechanisms included splitting, primitive denial, magical undoing, and rationalization. Cognitive functions were globally preserved, although vulnerable under conditions of intense emotional activation, particularly when bodily perception became salient. Psychodiagnostics assessment (SCID-5-CV, SCID-5-SPQ, EDI-3, BES, and BSQ) revealed clinically significant scores on measures of bulimic symptomatology, body dissatisfaction, low self-esteem, and personal and interpersonal alienation, outlining a profile characterized by profound feelings of inadequacy, inner emptiness, and relational difficulties. Psychometric findings indicated marked body dissatisfaction (Cooper et al., 1987), uncontrolled eating behavior, and binge-eating episodes. Significant levels of personal and interpersonal alienation, interoceptive deficits, and difficulties in emotional regulation also emerged (Garner et al., 2004). Clinically, defensive operations of splitting, denial, and rationalization were evident, together with fragile ego boundaries and a predominantly fusional mode of functioning. The body appeared to serve as the primary channel of expression and containment. Although no sufficient criteria for a structured personality disorder were identified, dependent, obsessive-compulsive, and schizoid personality traits were present. According to DSM-5-TR criteria (APA, 2022), the diagnostic hypothesis was consistent with Binge-eating disorder (First et al., 2016). From a psychodynamic perspective, the patient’s functioning appeared organized around a fragile psychic structure sustained by fusional relational modalities, in which the other assumes an indispensable regulatory function. The theme of the “double” permeates the patient’s developmental history and re-emerges in current relationships in the form of identity oscillations and difficulties in differentiation. Within this framework, the body may be viewed as a symbolic container through which unresolved aspects of the relational bond acquire psychological visibility. The body may be viewed as a symbolic container through which unresolved aspects of the relational bond acquire psychological visibility. The body may be understood as a site of condensation of the bond—a boundary that is simultaneously present and insufficient—while the eating symptom functions as a defensive attempt to preserve psychic continuity in the face of the threat of disintegration. References to her twin sister introduce a dimension of shared identity: “We have always been the same.” In this sense, the symptom may contribute to maintaining a sense of narcissistic continuity within a shared identity configuration
Mirror Twin
The second twin presented with remarkably similar characteristics, generating a clinical impression of déjà vu. Here too, psychological functioning was organized around a dominant sense of “we-ness,” with considerable difficulty in constructing an autonomous personal narrative.
The patient described persistent feelings of emptiness, insecurity, and a need for control. Psychodiagnostics assessment revealed interoceptive deficits, affective difficulties, perfectionistic tendencies, and excessive self-control, together with marked feelings of inadequacy and global psychological maladjustment (Garner et al., 2004). Findings were also suggestive of probable Binge-eating disorder and significant body dissatisfaction.
Interpersonal relationships appeared fragile and were experienced as sources of disappointment and misunderstanding. Emotional intimacy tended to activate disorganization and withdrawal, with separation experienced as a profound threat.
Eating behavior assumed a self-soothing function: “When I eat, everything stops.” The body became both a container for anxiety and a shared psychic space linked to the twin sister. Integration of clinical and psychometric data allowed for a multidimensional understanding of psychopathological functioning, highlighting a structure characterized by Self-fragility, difficulties in affect regulation, and a predominantly fusional relational organization, supported by defenses such as denial and splitting (Evans et al., 2002).
The striking symptomatic convergence between the two sisters suggests an intersubjective organization of the symptom: obesity and binge eating are not merely individual disorders but also expressions of mutual belonging. From an analytical perspective, the sibling complex may be hypothesized to contribute to the symbolic organization of bodily experience, transforming the body into a shared psychic territory.
The Twin Relationship
The clinical narrative revealed a relationship characterized by profound symbiosis. Enrica and Carla frequently spoke in the first-person plural: “we,” “we feel,” “we decided.” Individual differences were minimized or denied, and every attempt at subjective self-assertion was followed by guilt, anxieties of betrayal, or fantasies of reciprocal abandonment. The twin sister appears to function as a narcissistic double, guaranteeing continuity of identity and affective containment. Separation, even when merely symbolic, is experienced as a threat to psychic survival. The twin may function, at times, as an imaginal representation of aspects of the Self that have not yet been fully differentiated. This is theoretically safer because Jung would not strictly identify an actual person with the Self archetype.
The Body as the Site of the Bond
In both sisters, obesity emerged in a strikingly similar configuration with respect to onset, course, and resistance to treatment. Gradually, the body became the primary site through which the sibling bond was inscribed: a body that is expansive, space-occupying, and resistant to transformation.
Symbolically, the obese body appears to function as:
- a shared container preserving a sense of unity;
- a defensive barrier protecting against external relationships experienced as intrusive;
- a concrete boundary compensating for the fragility of individual psychic boundaries.
The bodily symptom thus assumes a relational function: maintaining resemblance, visible continuity, and a shared destiny. From a psychodynamic perspective, the body may be viewed as a symbolic vessel through which experiences of psychic undifferentiation are expressed.
Obesity may be interpreted as an embodied representation of aspects of the sibling bond that remain organized around fusion rather than differentiation.
Conclusions
From a psychodynamic and analytical psychological perspective, the individuation process appears to be hindered by a primary identification that has not achieved sufficient differentiation. Rather than being recognized and integrated, elements that may be associated with the Shadow appear to find expression through bodily experience. The twin sister may assume the psychological function of an alter ego, protecting the individual from confronting the existential solitude required by the emergence of the Self (Jung, 1954). The body may symbolically reflect aspects of psychic experience that have not yet undergone transformation. a state of nigredo (Jung, 1944) unable to initiate the alchemical process of differentiation. From this perspective, obesity may be approached as both an individual symptom and a symbolic expression of relational and potentially archetypal dynamics.
Within this framework, the twin sister represents more than a concrete relational object. She assumes a symbolic and archetypal significance, embodying a liminal figure situated between the ego and the Shadow, between the Self (Jung, 1954) and the inner Other. The sibling is often the first “similar other” through whom the experience of difference emerges within the same generational field, functioning simultaneously as mirror, rival, and psychic double. The figures of the double described by Kaës may be interpreted, from a Jungian perspective, as constellating aspects commonly associated with the Shadow (Jung, 1954). The Shadow encompasses those aspects of the personality that the ego fails to recognize as its own, yet which continue to operate within both psychic and relational life. The twin may become a particularly significant recipient of projections involving disowned or insufficiently integrated aspects of psychic life(Jung, 1951).
Particularly significant is the theme of psychic bisexuality. Kaës (2009) interprets it as a defense against separation and castration, whereas Jung’s reflections on psychic wholeness and the symbolic conjunction of opposites suggest the possibility of an original state of relative undifferentiation that precedes the development of conscious oppositions. (Jung 1944).
Within the twin fantasy, the sister may therefore function as an imaginal support for preserving the illusion of this primordial unity, thus avoiding the painful task of differentiation.
The individuation process necessarily requires the renunciation of fusion and the acceptance of psychic solitude (Jung, 1954). When the sibling complex remains fixed, the sibling persists as a concrete or fantasmatic object that hinders access to genuinely other-oriented relationships. When symbolization becomes possible, however, the sibling assumes a mediating function within individuation, compelling the ego to confront its own limitations and the irreducible plurality of psychic life.
The fratricidal myths discussed by Kaës (2009), such as Cain and Abel or Eteocles and Polynices, portray in archetypal form the failure to integrate the fraternal Shadow. Jung (1954) emphasized that the failure to reconcile psychic opposites leads to destructive polarization and potentially lethal forms of splitting (Jung, 1951). Conversely, the transformation of primordial rivalry into symbolic relatedness opens the way toward ethical and cultural development.
From a therapeutic perspective, the sibling complex constellates transferential contents that are not only personal but also transpersonal in nature. The analyst, too, is called upon to confront his or her own sibling complex and the archetypal images of the double and the rival activated within the analytic field.
Psychotherapeutic work with twins requires sensitivity to sibling dynamics. Every movement toward autonomy may reactivate archaic anxieties of loss, abandonment, and guilt. The risk is that the bodily symptom becomes reinforced as the final defense against separation. The clinical aim is therefore not forced separation, but the gradual construction of symbolic boundaries capable of supporting differentiation without psychic trauma.
In conclusion, the sibling complex may be understood as a fundamental threshold within the individuation process: a passage from the narcissistic illusion of unity toward the symbolic possibility of relationship; from fusion to differentiation; from sameness to multiplicity. In this light, the sibling is not merely the one who divides love, but also the one who opens the individual to the possibility of the world.
From this perspective, recognition of the sibling complex becomes essential if the body is no longer to remain the sole site upon which the bond is inscribed. Where the body continues to carry the undifferentiated, individuation remains suspended. Within an analytical psychological perspective, the gradual relinquishment of fantasies of primordial unity may create the conditions through which a more differentiated relationship to the Self can emerge (Jung, 1944).
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