Cited by 107Digital Mental Health InterventionsEthics and Social Impacts of AISocial Robot Interaction and HRI

Technological folie à deux: feedback loops between AI chatbots and mental health

Open access
Dohnány, Sebastian, Kurth-Nelson, Zeb, Spens, Eleanor, Luettgau, Lennart, Reid, Alastair, Gabriel, Iason, Summerfield, Christopher, Shanahan, Murray +1 more·2026·Nature Mental Health

Abstract

Artificial intelligence chatbots have achieved unprecedented adoption, with millions now using these systems for emotional support and companionship in contexts of widespread social isolation and capacity-constrained mental health services. While some users report psychological benefits, concerning edge cases are emerging, including reports of suicide, violence, and delusional thinking linked to emotional relationships with chatbots. To understand these risks we need to consider the interaction between human cognitive-emotional biases and chatbot behavioural tendencies, the latter including companionship-reinforcing behaviours such as sycophancy, role-play and anthropomimesis. Individuals with preexisting mental health conditions may face increased risks of chatbot-induced changes in beliefs and behaviour, particularly where these conditions manifest in altered belief-updating, reality-testing, and social isolation. To address this emerging public health concern, we need coordinated action across clinical practice, AI development, and regulatory frameworks.

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  • Common concerns associated with LLM-CBs are hallucinations (incorrect information generated by LLM-CBs, including incorrect health advice) and sycophancy (LLM-CBs' tendencies to agree with the user despite potentially incorrect or harmful statements).

    “Common concerns associated with LLM-CBs are hallucinations (i.e., incorrect information generated by LLM-CBs, including incorrect health advice)15 and sycophancy (i.e., LLM-CBs’ tendencies to agree with the user despite potentially incorrect or harmful statements)16.”

    From A scoping review on the mental health harms of LLM-based chatbots (2026) · cites this paper as [16]

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  • Dohnány et al. introduced the term folie à deux (i.e., induced psychosis) or bidirectional belief amplification in the context of "AI psychosis," noting that users' inputs feed LLM-CBs' memory and chatbots adapt to delusional thoughts.

    “Dohnány et al. introduced the term folie à deux (i.e., induced psychosis) or bidirectional belief amplification in the context of “AI psychosis,” noting that users’ inputs feed LLM-CBs’ memory and chatbots adapt to delusional thoughts16.”

    From A scoping review on the mental health harms of LLM-based chatbots (2026) · cites this paper as [16]

    In “Feedback loops and technological folie à deux” (page unavailable), the paper applies folie à deux to human–chatbot interactions and describes bidirectional belief amplification, including chatbot adaptation to user-expressed paranoia. It says users’ reinforced beliefs feed back through conversational context, but does not establish that those inputs are stored in chatbot memory; its discussion of external memory systems describes future systems. (LLM, conf=0.84)

    Experimental — accuracy not yet measured
  • As LLM-CBs adapt to the user's delusional input, reality checks may be outsourced to LLM-CBs.

    “As LLM-CBs adapts to the user’s delusional input16, reality checks may be outsourced to LLM-CBs140.”

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Research works printed but not linked: 8

  1. [11]Robb MB Mann S Talk, trust, and trade-offs: How and why teens use AI companions Common Sense Media San Francisco, CA 2025 Preprint at
  2. [17]How people are really using gen AI in 2025 Harvard business review 2025
  3. [33]Huang L A survey on hallucination in large language models: Principles, taxonomy, challenges, and open questions ACM Trans Inf Syst 2025 43 1 55
  4. [52]Sharma M Towards understanding sycophancy in language models arXiv [csCL] 2023
  5. [70]Bai Y Constitutional AI: Harmlessness from AI Feedback arXiv [csCL] 2022
  6. [78]Ibrahim L Sofia HF Rocher L Training language models to be warm and empathetic makes them less reliable and more sycophantic arXiv [csCL] 2025
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  8. [92]Park JS Generative agent simulations of 1,000 people arXiv [csAI] 2024

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Authors
Dohnány, S., Kurth-Nelson, Z., Spens, E., Luettgau, L., Reid, A., Gabriel, I., Summerfield, C., Shanahan, M., & Nour, M. M.
Affiliations
  • University of Oxford (GB)
  • University College London (GB)
  • Oxford Health NHS Foundation Trust (GB)
  • University of London (GB)
  • Imperial College London (GB)
Corresponding author
Nour, Matthew M.
Venue
Nature Mental Health
Published
2026-03-10
Volume
4
Issue
3
Pages
336-345
ISSN
2731-6076 (ISSN-L)
OpenAlex
W7134947688
Cited by
51
References
95
Citations by year
2026: 51
FWCI
300.37
Type
journal article
Language
en
Open access
Locations
  • Nature Mental Health (publishedVersion)
  • PubMed (publishedVersion)
  • PubMed Central (publishedVersion, cc-by)
  • MPG.PuRe (Max Planck Society) (submittedVersion)
Funders
  • Wellcome Trust (315364/Z/24/Z)
  • Merton College, University of Oxford (NA)
Topics
  • Social Sciences › Psychology › Applied Psychology › Digital Mental Health Interventions
  • Social Sciences › Safety Research › Ethics and Social Impacts of AI
  • Social Sciences › Psychology › Social Psychology › Social Robot Interaction and HRI
Keywords
AI chatbots, mental health, emotional support, social isolation, sycophancy, role play, belief updating, suicide, AI regulation

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