Not yet recruitingNot ApplicableInterventional

Developing and testing a new treatment for Posttraumatic Stress Disorder (PTSD): Retrieval dependent Nitrous Oxide Therapy (R-NOT)

This study is exploring a new treatment, called R-NOT, for Posttraumatic Stress Disorder (PTSD). PTSD can cause upsetting memories, and this treatment aims to make those memories less powerful. It involves briefly recalling a traumatic memory, then breathing a mix of 50% nitrous oxide and 50% oxygen (like the 'gas and air' used in childbirth) for about an hour. Researchers want to see if this treatment is easy for healthcare professionals to give and if people with PTSD find it acceptable and useful. This study will help them decide if larger studies are needed. Participants will be asked to complete questionnaires and use an online diary to track their memories.

At a glance

Status

Not yet recruiting

Phase

Not Applicable

Sponsor

University College London

Enrolment target

Start

08 Jun 2026

Estimated completion

31 Jul 2026

Posttraumatic stress disorder (PTSD)

What is this study about?

Posttraumatic Stress Disorder (PTSD) is a condition that can develop after someone experiences or witnesses a very upsetting event. It can cause a lot of difficulties, like having unwanted, distressing memories (often called 'intrusive memories'), avoiding things that remind you of the event, and feeling constantly on edge. While there are treatments available for PTSD, they can sometimes take a long time to work and aren't effective for everyone.

This study is looking at a new treatment called Retrieval-dependent Nitrous Oxide Therapy (R-NOT). It focuses on helping with one of the most troubling symptoms of PTSD: those intrusive memories. The idea behind R-NOT is that by recalling an upsetting memory and then breathing in a mixture of gas (50% nitrous oxide, commonly known as 'gas and air', mixed with 50% oxygen), we might be able to make the emotional impact of that memory weaker. This means the memory might still be there, but it won't feel as distressing or powerful.

The main goal of this particular study is to see if R-NOT can be developed in a way that is easy for trained professionals to use, and to find out if people with PTSD think it's a helpful and acceptable treatment. The results from this small study will help researchers decide if they should move forward with bigger studies involving more people. If successful, R-NOT could potentially become an additional treatment option for PTSD available through the NHS, possibly offering quicker relief than some current treatments.

Key takeaways

This study tests a new treatment (R-NOT) for PTSD's upsetting memories.
R-NOT involves recalling a memory then breathing 'gas and air' for an hour.
The goal is to weaken the emotional power of traumatic memories.
It aims to find out if R-NOT is easy to use and helpful for patients.
Participation lasts about 14 days, with clinic visits and diary tracking.
Side effects are usually mild and temporary, linked to 'gas and air'.

Who may be eligible?

This study is looking for people aged 18 to 65 years old who have been diagnosed with PTSD and are currently waiting for psychological treatment. You would need to be referred by an NHS Talking Therapies Service in London to take part.

To be eligible, you should be having at least one distressing intrusive memory each week and be able to understand and speak English well enough to complete questionnaires and describe your memories. You'll also need access to the internet and a smartphone every day. If you are a woman who could become pregnant, you would need to agree to use effective contraception during the study and for a short time after treatment.

You cannot take part if you are currently having psychological therapy for PTSD, or if you've recently changed your psychiatric medication or plan to during the study. Other reasons you might not be able to participate include using specific recreational drugs, having certain medical conditions (like a collapsed lung or severe asthma), or if you are pregnant or trying to get pregnant.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

Are you between 18 and 65 years old?
Do you have a PTSD diagnosis and are waiting for talking therapy?
Do you experience at least one distressing memory each week?
Can you understand and speak English well enough for questionnaires?
Are you able to use contraception if you are a woman who could become pregnant?

Answer every question to see your result.

What does participation involve?

If you are interested and meet the initial criteria, you will first have a screening call with the R-NOT study team to make sure it's safe and suitable for you to take part. The entire study experience will last for about 14 days.

During this time, you will visit two locations in London: the Clinical Psychopharmacology Unit (CPU) at University College London (UCL) for a baseline appointment, and the Clinical Research Facility (CRF) at University College London Hospital (UCLH) for the treatment session. A trained healthcare professional will carry out the treatment session. After this, you'll have a follow-up call with the research team. To help track how the treatment affects your memories, you'll also be asked to use an online diary and a smartwatch to record any upsetting memories about the event for one week before and one week after your treatment visit.

Potential risks and benefits

While this treatment won't guarantee an improvement in your PTSD symptoms, if R-NOT works as expected, you might find that your symptoms get better. However, it's also possible that you won't experience any benefits. As with all research studies, there are some risks involved, but the 'gas and air' used (50% nitrous oxide) is generally very safe, and side effects are usually mild and disappear quickly once you stop breathing the gas. Common, short-lived side effects include feeling dizzy, sleepy, or a bit 'floaty', and some people might feel sick or vomit. The research team is trained to help you if you feel distressed while breathing the gas. Serious side effects are extremely rare with the small amount of gas used in this study, but there is always a very tiny chance of an unexpected event. Remember, you can always change your mind and decide to leave the study at any time.

Locations (2)

Some site locations are approximate. We're improving this — please verify with the trial team before travelling.

University College London, Clinical Psychopharmacology Unit
City only
London, England
North London NHS Foundation Trust
City only
London, England

Common questions

What is 'gas and air'?

'Gas and air' is a mixture of 50% nitrous oxide and 50% oxygen. It's often used in pain relief, for example, during childbirth, because it helps you feel more relaxed and can reduce pain.

How long does treatment take?

The actual treatment where you breathe the gas and air will last for about an hour. However, your whole visit to the clinic will take longer to allow for preparation and recovery time.

Will this cure my PTSD?

This is a new treatment being tested, so we don't know for sure if it will cure PTSD. The aim is to make intrusive memories less distressing, and if successful, this could reduce your overall PTSD symptoms. This study will help us find out more.

Where does the study take place?

You'll need to visit two locations in London: University College London (UCL) for a first appointment and University College London Hospital (UCLH) for the treatment session.

Can I still take part if I'm having other talking therapy?

No, if you are currently engaged in psychological therapy for PTSD, you will not be able to participate in this study. This helps researchers understand the effect of R-NOT more clearly.

How to find out more

Tallulah Chaplain

r-not@ucl.ac.uk +44 (0)207 679 2000 Official trial record

Always speak to your GP or specialist before deciding to take part in a study.