Silexan in the Treatment Of Posttraumatic Stress Disorder Trial
Key facts
- Who runs it
- Deakin University
- Where
- Australia4 sites in 1 countryChoose a country to see its sites
- Trial code
- Status
- Recruiting
- Phase
- Phase 3
- People taking part
- 278 people, planned
- Started
- 26 Aug 2024
- Expected to end
- Jun 2027
- Type of study
- Interventional, 2 groupsOne group gets a placebo (a dummy treatment), for comparison.
- Treatments tested
- Silexan
- Placebo
- Record updated
- 18 December 2025
Who can take part
- Age
- 18 years and older
- Sex
- Women and men
- Healthy volunteers
- Cannot take part
The registry criteria, word for word
Show all 18 criteriaShow less
Who can take part
- Aged 18 years or over
- Fluent in English
- Meet DSM-5 criteria for PTSD, irrespective of occupation (e.g. first responder, police officer, ex-military or civilian), determined using the Mini International Neuropsychiatric Interview 7.0.2
- Have a score on the PTSD Checklist for DSM-5 (PCL-5) equal to or over 33
Who cannot take part
- Commencement of a trauma-focussed psychotherapy (including Prolonged Exposure, Cognitive Processing Therapy and Eye Movement Desensitisation and Reprocessing) within 3 months of screening
- Commencement or change in dose of psychoactive medications within 4 weeks of screening
- Participants will be asked not to initiate psychotherapy or change the dose of psychoactive medications during the course of the study except in clinically urgent circumstances; if this becomes necessary, a decision will be made on a case-by-case basis with regard to retaining the participant or terminating their participation
- Lifetime history of a psychotic or bipolar disorder, or dissociative identity disorder
- Moderate or severe alcohol or other substance use disorder within 3 months of screening
- Borderline Personality Disorder (BPD)
- Acute or unstable medical illness or other significant medical condition, that would make participation in the trial unsafe or inappropriate
- Any other condition that in the opinion of the research team is likely to make completion of the trial requirements infeasible
- Are currently serving in the Australian Defence Force
- Active suicidal or homicidal ideation
- Pregnancy, lactation or unwillingness to use an acceptable method of contraception (required for both males and females who are of reproductive potential and sexually active with partners of the opposite sex) through the duration of participants' involvement in the study up to and including week 16. Participants will also be advised not to donate eggs or sperm during the study period
- Severe acquired brain injury
- Individual is not eligible for public mental health services due to their visa status in Australia or for any other reason
- Inability to understand or speak English to the extent necessary to give informed consent and complete the trial (researcher or clinician-determined)
This trial has no sites in United States.
It has sites in one country. Choose a country to see its sites.
About the trial
What the trial wants to find out
Posttraumatic stress disorder (PTSD) is a common and debilitating mental illness. Current treatments for PTSD include psychotherapy and antidepressant medications. Many patients are unable to tolerate psychotherapy for PTSD and drop out of it. In addition, its effectiveness is limited. Up to 50 percent of patients who receive psychotherapy do not benefit from it. Antidepressant medications have only small benefits in PTSD. They also have unpleasant side effects that can make patients unwilling to take them. There is an urgent need to develop new treatments for PTSD that work and are well-tolerated. Silexan has the potential to provide an important alternative treatment for PTSD.
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Silexan is derived from lavender oil. It is taken orally in the form of capsules. It is currently available over-the-counter in 14 countries, including Australia and the United States. Previous research has shown that it is an effective treatment for anxiety disorders, including Generalized Anxiety Disorder. It is also well-tolerated by patients. The only side effects that have been identified so far are mild gastrointestinal symptoms (including burping and breath odour) and these are uncommon. The results of a small pilot study suggest that Silexan may also be effective and well-tolerated in PTSD.
The STOP trial is a clinical trial that aims to investigate whether adding Silexan to treatment-as-usual improves PTSD symptoms in adults with PTSD. The trial will recruit 278 participants. Participants will be randomly assigned to take Silexan or a placebo (look-alike dummy pills) daily in addition to their usual medications for 12 weeks. The severity of their PTSD symptoms will be assessed prior to and at the end of this 12-week period.
The STOP trial has the potential to obtain definitive evidence regarding whether Silexan helps treat symptoms of PTSD. If Silexan is found to be an effective treatment for PTSD, the pool of patients who could potentially benefit from this treatment includes any adults with PTSD. Silexan is already available over-the-counter at a relatively low cost so there will be few barriers to accessing this treatment.
The 2 groups in the trial
- Silexan 160 mgTreatment being tested
Participants in the Silexan arm will take Silexan 160 mg daily in the morning for 12 weeks in addition to their usual prescribed psychoactive medications. Participants will be followed up at 2, 4, 6, 8 and 12 weeks of the intervention period, as well as at 4 weeks post-treatment (off-treatment follow-up period).
Treatment: Silexan
- PlaceboPlacebo, for comparison
Participants in this arm will take two placebo capsules daily in the morning for 12 weeks in addition to their usual medications. Participants will be followed up at 2, 4, 6, 8 and 12 weeks of the intervention period, as well as at 4 weeks post-treatment (off-treatment follow-up period).
Questions to ask the study team
- How often do I need to come in, and for how long each time?
- Are travel costs paid?
- Can I keep my own doctor?
- What happens if I want to stop?
Contact the study team: see the registry record → Contacts and Locations
Print a page for my doctorData and sources
- Registry record
- Listed on ClinicalTrials.gov.
- Official title
- Silexan in the Treatment Of Posttraumatic Stress Disorder (STOP) Trial
- Publications
- The Silexan in the Treatment Of Posttraumatic stress disorder (STOP) trial: protocol for a 12-week randomised controlled trial of adjunctive Silexan for PTSD.BMC complementary medicine and therapies, 2026
- Record updated
- 18 December 2025