Science

The ideas behind it, and their evidence.

TwentyThird stands on a century of psychodynamic thinking and on newer research into AI and mental health. Here is what we draw on, what the evidence says, and what it does not say about us.

The ideas

Three ideas we build on.

repetition

We repeat what we have not understood.

Freud described how people return to the same painful situations without meaning to (Beyond the Pleasure Principle, 1920). The AI looks for that return across the years you describe.

language

The way you say it carries meaning.

Jacques Lacan argued that the unconscious works like a language — in slips, substitutions and the words we choose. The AI reads your own words closely, not only what they are about.

attachment

Early bonds shape later ones.

John Bowlby's attachment theory (Attachment, 1969) and the research that followed show how early relationships shape how we handle closeness as adults. Your readings on closeness and relationships draw on it.

The evidence

What research says, and about whom.

These studies are about psychodynamic therapy with human therapists, and about other AI tools. None of them studied TwentyThird.

Long-term psychodynamic therapy

A meta-analysis of 23 studies (Leichsenring & Rabung, JAMA, 2008) found long-term psychodynamic therapy more effective than shorter therapies for complex mental disorders.

AI can help, under conditions

The first randomised trial of a generative-AI chatbot for mental health (Heinz et al., NEJM AI, 2025) found larger symptom reductions than in a control group over eight weeks. Its authors say no AI is ready to work in mental health without human oversight.

And can harm without oversight

A 2025 study led from Stanford (Moore et al., ACM FAccT) found that large language models used as therapists showed stigma towards some conditions and answered some crisis scenarios inappropriately. That is why a licensed human stays in the loop.

Human therapy, not TwentyThird

Psychodynamic work keeps working after it ends

Across 23 trials, short-term psychodynamic therapy had a large effect when it ended, and a larger one nine months later.

0.8 and above counts as a large effect.

Abbass et al., Cochrane review (2006): 23 trials, 1,431 patients; as summarised in Shedler, American Psychologist 65(2), 2010. Human therapy, not TwentyThird.

What we do not claim

The honest edges.

That TwentyThird has been tested in a trial.

It has not. If we run an evaluation, we will publish it with its method.

That it treats anything.

It supports self-understanding between sessions. Diagnosis and treatment are a clinician's work.

That the 23-day cycle is real.

It was Fliess's hypothesis. We keep it as a name; science does not support it.

References

Where to read further.

Studies

  1. Abbass, A. A., Hancock, J. T., Henderson, J., & Kisely, S. (2006). Short-term psychodynamic psychotherapies for common mental disorders. Cochrane Database of Systematic Reviews.
  2. Shedler, J. (2010). The efficacy of psychodynamic psychotherapy. American Psychologist, 65(2), 98–109. doi:10.1037/a0018378
  3. Leichsenring, F., & Rabung, S. (2008). Effectiveness of long-term psychodynamic psychotherapy: a meta-analysis. JAMA, 300(13), 1551–1565.
  4. Heinz, M. V., Jacobson, N. C., et al. (2025). Randomized trial of a generative AI chatbot for mental health treatment. NEJM AI. doi:10.1056/AIoa2400802
  5. Moore, J., Grabb, D., Agnew, W., Klyman, K., Chancellor, S., Ong, D. C., & Haber, N. (2025). Expressing stigma and inappropriate responses prevents LLMs from safely replacing mental health providers. ACM FAccT. arXiv:2504.18412

Books

  1. Sigmund Freud · 1920 — Beyond the Pleasure Principle
  2. Sigmund Freud · 1900 — The Interpretation of Dreams
  3. Jacques Lacan · 1966 — Écrits
  4. Jacques Lacan · 1973 — The Four Fundamental Concepts of Psychoanalysis
  5. John Bowlby · 1969 — Attachment
  6. Allan Schore · 1994 — Affect Regulation and the Origin of the Self
  7. Peter Fonagy et al. · 2002 — Affect Regulation, Mentalization, and the Development of the Self

From theory to your own patterns.

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