Mentalization-Based Therapy for Psychosis Shows Durable Effects at 5-Year Follow-Up
- Five-year follow-up of a multi-centre RCT (n=84): mentalization-based treatment for psychotic disorder (MBTp) vs treatment as usual (TAU)
- MBTp patients still scored significantly better on social functioning compared to baseline at 5 years post-treatment (ηp² = .25) — a large, clinically meaningful effect
- Improvements in mentalizing capacity were maintained — patients retained the ability to understand their own and others' mental states
- The original trial showed MBTp superiority at 6 months; this follow-up confirms the effects are durable, not transient
Mentalization-based treatment was originally developed for borderline personality disorder. Its adaptation for psychosis — MBTp — is newer and less established. This Psychological Medicine study answers the question that every commissioner and funder asks: does the effect last? At five years, the answer is yes.
Why 5-year data matters
Most psychotherapy trials for psychosis report 6-12 month outcomes. The clinical question for psychosis treatment is different from depression or anxiety: these are long-term conditions requiring long-term evidence. A therapy that shows benefit at 6 months but fades by year 2 is a different proposition from one that remains effective at year 5.
The effect size on social functioning (ηp² = .25) is large. Social functioning — the ability to maintain relationships, engage in community activities, manage daily tasks — is arguably the outcome that matters most to people living with psychosis. It is also the outcome that medication alone consistently fails to improve.
The mentalizing mechanism
MBTp works by improving mentalizing — the capacity to understand behaviour in terms of mental states (beliefs, desires, feelings, intentions). In psychosis, mentalizing is disrupted: difficulties reading others' intentions contribute to paranoia, social withdrawal, and interpersonal conflict.
The 5-year data shows that mentalizing improvements were maintained. This suggests that MBTp does not just produce a temporary therapeutic effect — it changes a cognitive capacity that patients retain and continue to use after treatment ends. This is the mechanism that distinguishes MBTp from supportive interventions that feel good during delivery but do not create lasting change.
For your practice
If you work with psychosis patients and have access to MBT training, this study provides the long-term evidence that was previously missing. For service planners: MBTp requires skilled therapists and sustained commitment, but the 5-year durability means the cost-per-quality-adjusted-year is more favourable than it appears from short-term data alone.
Mentalization-based treatment for psychosis maintains significant social functioning improvements 5 years after treatment — the first long-term evidence that a psychological therapy for psychosis produces durable change.
46 of 84 original participants assessed at follow-up (55% retention). No evidence of selective dropout, but attrition limits certainty. Single treatment model — generalisability to other MBT adaptations unknown. Social functioning is multi-determined — attribution to MBTp specifically requires caution.