THE ODDESSI TRIAL
The ODDESSI Trial: Evidence, Findings & Systemic Implications
A decade of research on Open Dialogue in public mental health systems, published August 2026 in The Lancet Psychiatry.
Pilling, S., et al. (2026). Open Dialogue versus treatment as usual for adults presenting in crisis to mental health services in England (the ODDESSI Trial): a multisite cluster-randomised trial. The Lancet Psychiatry.
The Global Costs of the Current System
When someone experiences a mental health crisis in the traditional Western model, whether in Australia or the UK, they typically encounter a fragmented maze.
They might contact their GP or present to an emergency department. They may be triaged by a crisis team, and if things stabilise, they may be handed over to a community mental health team. Throughout this process, the individual often sees different clinicians each time and has to repeat their story again and again. Family and friends are rarely invited into the conversations, and notes are kept secret from the person they are about.
The human cost of this approach is profound. As highlighted in numerous international mental health inquiries, people consistently describe feeling lost, unheard, and treated like a diagnosis rather than a person. Families and other loved ones feel sidelined, staff feel overwhelmed, hospital beds overflow, and people are frequently detained against their will.
Before ODDESSI: What the Original Finnish Data Showed
In the 1980s, Jaakko Seikkula and his colleagues in Western Lapland did something radical. When someone was in crisis, they brought the person, their family, their friends, and clinical staff together in one room. They listened to everyone rather than relying solely on a clinician’s diagnosis. They made decisions together, kept the same team throughout the process, and stayed connected even after the crisis passed.
Research consistently associates the original Western Lapland model with strong long-term outcomes over its first decades of use. These figures come from naturalistic, non-randomised studies in Finland, not from ODDESSI, which was designed specifically to test whether these results would hold up in a large randomised trial within the NHS.
82%
NO RESIDUAL PSYCHOTIC SYMPTOMS LEFT AFTER 5 YEARS
86%
RETURNED TO STUDY OR WORK
29%
REQUIRED MEDICATION
The ODDESSI trial was built to answer a critical question: could an approach that originated in Western Lapland work at scale within a large, complex public health system like the UK NHS?
What is Open Dialogue?
Open Dialogue brings the person in crisis, their family and friends, and mental health staff together in one meeting. There are no hidden notes and no diagnoses handed down. It relies on genuine conversation aimed at understanding what is happening and finding a way forward together.
What is ODDESSI?
ODDESSI stands for Open Dialogue: Development and Evaluation of a Social Network Intervention for Severe Mental Illness.
It is the largest randomised controlled trial ever conducted on Open Dialogue.
The overarching research was led by Principal Investigator Professor Stephen Pilling (University College London) and Clinical Lead Dr Russell Razzaque, alongside a large team of academics, clinicians, and lived-experience researchers from across England. The full author list and study details are available via the official UCL ODDESSI Trial Hub.
The Trial at a Glance
The Difference: Peer-Supported Open Dialogue
A critical distinction of the ODDESSI trial was that it tested Peer-Supported Open Dialogue.
In the original Finnish model, network meetings were facilitated by traditional clinical staff (nurses, psychologists, psychiatrists) who had trained in dialogical practice. ODDESSI introduced a new dynamic. The trial explicitly trained peer practitioners to co-facilitate these meetings alongside clinicians. These were individuals with lived experience of mental health crises.
The research team hypothesised that this integration of lived experience would help flatten the clinical hierarchy. The aim was to ensure that the person in crisis was supported by someone who understood the territory of psychological distress from the inside out.
How the Trial Worked
The ODDESSI trial was not just one big test. It was built in five meticulous phases to ensure accuracy at every step.
The Trial Findings
The published data presents a dataset reflecting what occurred when care shifted toward network involvement and relational continuity:
- Primary Outcome (Time to Relapse): The trial did not show a statistically significant difference in time to relapse between Open Dialogue and standard care over the two-year follow-up period.
- Inpatient Hospital Admissions: Participants receiving Open Dialogue had significantly higher odds of avoiding hospital admissions, resulting in a substantial reduction in acute bed days.
- Crisis Re-Referrals: Rates of re-referral back into crisis services were significantly lower in the Open Dialogue group.
- User Experience: Participants reported significantly higher satisfaction, feeling listened to, respected, and involved in their decisions.
- Social Network Size: The trial measured no statistically significant increase in the size or density of participants’ social networks over time.
Methodologically, participants and clinicians were not blinded to the intervention during the trial.
What Does This Mean?
ODDESSI marks a major milestone for relational mental health care. It moves the conversation beyond anecdote and gives our field robust empirical data to examine, debate, and build upon.
While the trial demonstrates that dialogical practice does not erase the recurrence of psychological distress, it points to the value of relational continuity: keeping people out of acute hospital beds, preventing crisis bounce-backs, and holding space with dignity.
Dialogue Room will be unpacking these results in the coming months.
Dive Deeper: Trial Mechanics & FAQ
Explore Our Work
What started as a single vision in Australia, making Open Dialogue network meetings accessible to families across Australia, has slowly expanded into something much larger.
Dialogue Room: Where it Started
This is where it all began, in Australia. We started with a simple vision: making Open Dialogue network meetings accessible to families across Australia. From that foundation, we’ve slowly expanded into something larger, continually exploring different ways to bring dialogical practice into the way we live and work. Making it the default, not the exception.