For Patients Friends and Relatives

How to help someone with depression , who may benefit from a new approach.


This page tells you a bit more about this trial if you are close to someone who is thinking about participating.

You must also read the Official Participant Information Sheet if you want to take part.


Frequently Asked Questions


What is the PsiDeR Trial?

The PsiDeR trial is a placebo-controlled clinical trial of psilocybin in difficult-to-treat clinical depression. The aim of the trial is to understand whether psilocybin, given with appropriate psychological support, is a feasible, safe and effective treatment for difficult-to-treat depression when compared to a placebo that is also given with the same psychological support. We need to compare psilocybin to a placebo because this is the only way of knowing for sure how safe and effective psilocybin is when compared to the passage of time.

What is Psilocybin?

Psilocybin is a classical psychedelic drug, like lysergic acid diethylamide (LSD), mescaline and dimethyltryptamine (DMT). Psilocybin is naturally occurring. It is found in a variety of different mushroom species. People from different cultures have used psychedelics (in the form of psilocybin, mescaline and DMT) for thousands of years in ceremonial, sacramental and healing contexts. Psilocybin stimulates serotonin receptors in the brain. Serotonin is known to regulate mood.

What is the background to this trial?

Psilocybin was marketed as a medicine prior to 1970 in Europe and was used as a treatment for people with difficult-to-treat depression before it was legally restricted around 1970. When we looked at the trials from this period , we found that nearly 80% of people treated with psychedelics were judged by their doctors to have improved afterwards. These trials were generally not of good quality, so the results may not be accurate. This is why we need to do this trial, which is designed to a much higher standard to the trials performed prior to prohibition in 1970.

Can Psilocybin cause harm?

Like any drug, unpleasant effects can occur with psilocybin, however we think the chance of you being physically harmed by psilocybin itself is very low. In terms of toxicity to the body (physiological toxicity), the evidence suggests that psilocybin is safe when compared to other drugs.

In terms of toxicity to the mind (this is sometimes called a ‘bad trip’), the evidence suggests that the chance of this happening is related to the mind ‘set’ of the person who has taken the drug and the ‘setting’ within which the drug has been taken. Bad trips are more likely when people are unprepared and do not feel they are in a comfortable or safe setting. This is why we are providing everyone who participates in this trial with a dedicated therapist and chaperone who understand how psilocybin works. The therapist will get to know you, educate you about how psilocybin works and then be with you to help you through any difficult experiences you have. This is also why we will be giving the psilocybin in a safe, comfortable and supportive hospital setting. By doing these two things, we think that we will minimise the risk of serious adverse reactions. This is also the opinion of other research groups and individuals who have used psilocybin.

The UK government classifies psilocybin and all classical psychedelic drugs as some of the most dangerous and addictive drugs. The scientific evidence strongly indicates that this is not correct. Both users of , and experts in , recreational use of drugs and alcohol rate psilocybin mushrooms as one of the least harmful drugs. This does not mean that psilocybin is entirely ‘safe’ (no drug or treatment is entirely safe), but we are confident that psilocybin is not a drug that is toxic to the body and that it is a logical choice for further research as a treatment for depression, particularly depression that hasn’t improved with the usual treatments.

Can I Find Out More Information About the Effects of Psilocybin?

Yes. We have collaborated with other investigators to help you understand how psilocybin works and what the effects on you might be. <available soon>

What other research has been done?

We completed a smaller scale, pilot trial in 20 participants in 2016 . This showed that everyone who received psilocybin experienced an improvement in their depression scores, but for many people this was not sustained beyond about 1 month. However, some people remained depression free after 1 year and some people have remained depression free since we gave them the treatment in 2015. We do not know why some people respond so well and some people don’t. No one experienced a ‘serious adverse event’, which means a side effect that is life threatening or seriously debilitating.

Numerous other small-scale trials have been completed in the modern era using psilocybin and, to a lesser extent, DMT and LSD. Many more trials took place prior to 1970, after which classical psychedelics were legally restricted and most research stopped. You can read about many of these trials in the following summary paper on this page

Psilocybin in the form of mushrooms has been taken by millions of people in a variety of sociocultural contexts for, probably, thousands of years. Population research has documented associations between classical psychedelic use and positive mental health outcomes, such as reduced suicidal thoughts and need for Psychological Support. This is another reason we are motivated to test psilocybin in a clinical trial for depression.

Isn’t this ‘Just Another Drug Trial’?

Not really. Drug treatments are common in psychiatry and healthcare in general. However, many people with depression tell us that they do not like having to take daily medications. Psilocybin therapy is different, for the following reasons.

Firstly, if psilocybin was licensed as a medicine you would not need to take it every day. In fact, you may only need to take it once for it to help you. In this trial we will not give you any psilocybin to take home and you will receive a maximum of 2 doses of psilocybin. If you receive 2 doses, then the second dose will be about 6 weeks after the first dose. There is some evidence that psilocybin has a prolonged beneficial effect from just a single treatment in some people.

Secondly, if you are accepted onto this trial then we will ask you to slowly stop taking your existing depression medications, if you are taking any. This may be attractive to you if you are not happy with your current treatments or want to stop taking them for another reason. But it may also make your depression worse, so it is important to consider this carefully.

Thirdly, everyone in this trial will have an allocated therapist to provide psychological support, regardless of whether you receive psilocybin or not. We are testing psilocybin plus psychological support; not just psilocybin.

Fourthly, psilocybin works in a different way to traditional antidepressants. We are asking people in this study to give us regular blood samples and have 2 MRI brain scans so we can try to understand how and why psilocybin is working differently.

What will I need to do ?

If you want to participate, then the first thing to do is download and read the Participant Information Sheet. You must read this first and ask us any questions you have at … before you make a decision about whether you want to participate. You should also discuss it with friends and relatives you are close to. You can read some essential practical information about the trial here

How will my data be used?

King’s College London and the South London and Maudsley NHS Foundation Trust are the sponsors for this study based in the United Kingdom. We will be using information from you and/or your medical records in order to undertake this study and will act as the data controller for this study.

This means that we are responsible for looking after your information and using it properly. King’s College London and the South London and Maudsley NHS Foundation Trust will keep identifiable information about you for 15 years after the study has finished or until it is no longer used for research.

Your rights to access, change or move your information are limited, as we need to manage your information in specific ways in order for the research to be reliable and accurate. If you withdraw from the study, we will keep the information about you that we have already obtained. To safeguard your rights, we will use the minimum personally-identifiable information possible.

You can find out more about how we use your information here