Folie à deux: love, loyalty, and the limits of reality

Induced delusional disorder, historically termed Folie à Deux, is a complex clinical phenomenon in which delusional beliefs are transmitted from one individual to another within the context of a close relationship. It remains clinically relevant in situations characterised by social isolation, intense intimacy, and untreated psychiatric vulnerabilities.

This case study involves a married couple whose children were placed in kinship foster care after their infant daughter sustained near-fatal injuries. Both parents provided consistent and unwavering accounts, asserting that the infant experienced a single fall from a floor-based baby bouncer while the mother was briefly not supervising her. Despite medical evidence to the contrary, both parents denied the possibility of abuse and maintained their shared narrative under prolonged scrutiny.

Clinical assessment revealed striking similarities between the partners. Their histories, dating back to early adolescence, as well as their presentation, personality features, and results of psychometric testing were near-identical. The rigidity of their shared accounts, combined with these overlapping personality structures and their resistance to contradictory evidence, raised the possibility of induced delusional disorder. The case further illustrates established risk factors, including a longstanding intimate partnership, limited social engagement, and personality vulnerabilities.

The discussion considers the diagnostic complexities of induced delusional disorder, its implications for child protection, and therapeutic approaches. Particular attention is given to the potential role of conjoint psychotherapy in disrupting entrenched shared belief systems, as well as the importance of multidisciplinary collaboration in safeguarding children and supporting families.

Recognition of shared delusional dynamics is essential in family assessments. Failure to identify such processes may compromise child safety and hinder effective treatment planning. This case highlights the need for heightened awareness of induced delusional phenomena within forensic, clinical, and child welfare contexts.

Vivienne Perry is nearing completion of her Bachelor of Social Work at the University of the Sunshine Coast, with completion expected in November 2025. She is currently finalising her placement at Specialist Mind Care, where she has contributed to clinical assessments, psychometric testing, and medico-legal report writing. She operates a sole trader business and is in the process of collaborating with other professionals at Specialist Mind Care to launch two new ventures—one focused on emotional support animals, and the other on educational guidance and assessment reporting. Vivienne is dedicated to ethical, evidence-based practice in forensic mental health and plans to pursue further tertiary education. She will maintain an ongoing mentoring relationship with USC, supporting future students in the field.