Say a doctor invites a patient to test a new drug, because there is currently no effective drug to cure the illness. The patient says "I trust that what you are doing is best for my benefit. I'll take it."

But to avoid placebo/psychological effect, are they allowed to not fully disclose all side effects that the drug has, even when they know it? For example, they know ahead that the drug will make the patient nausea and body burning, but they just say that it will make them mildly dizzy. Is that ethical? The patient should have been informed all these effects before accepting the experiment – failing to do that breaks the trust they put on the doctor. But if telling their expectations to the side effects can distort the actual results.

I'm interested in the case of no treatment is available, but without a treatment the patients only continue to suffer the illness, not die.

Related: Is it ethical to deliberately provide incorrect information to participants in a psychological study?

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    While an interesting topic, I think the question if open for a broad spectrum of answers and even opinions.
    – bummi
    Jan 8 '19 at 10:27
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    @bummi I think Ooker is heading in a different direction, which is also interesting. In a clinical trial, side effects of a drug are tested. With approved drugs, one needs to disclose all side effects to the patient, but what during trial? Obviously, for the first few, one had no clue. But then - Do you say „50% of our test subjects experienced headaches“. This might indeed trigger a certain expectancy within the patient so that those patients, who know the side effects have more side effects. (Which I can guarantee at least on a study with n=1, myself.) This would totally ruin the trial.
    – Narusan
    Jan 8 '19 at 10:55
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    @Narusan maybe that's why we have double blind study? So that the researchers who give drugs to the patients don't really know the side effects? So that not only reduces expectancy in the patients, but also the expectancy in the researchers, which the patients may read out? Only the researchers who collect data can know the results, but they don't tell this to the ones who give guidance. The ones who know don't tell, the ones who tell don't know ;)
    – Ooker
    Jan 8 '19 at 11:13
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    @Ooker Let’s suppose you have a new medication for pancreatic cancer (a deadly disease). You need to test it, so you do a double-blind RCT with n=100. 50 of those patients will not be given access to the new, untested drug. This is why those studies are supervised all the time, and as soon as there is an indication that the new drug actually heals or decreases mortality, the trial will be stopped and all patients will be given access to the drug. It would be unethical to prevent n=50 from access to treatment.
    – Narusan
    Jan 8 '19 at 14:24

There are 2 questions here:

  1. Is not disclosing potential side effects during a clinical trial ethical?
  2. What does the "informed consent" of a clinical trial say about disclosing side effects?

According to Understanding Informed Consent by CenterWatch:

If you have given consent to participate in a clinical trial...you are entitled to the following rights:

  • To be told about all the risks, side effects, or discomforts that might be reasonably expected...


If you want to know details, such as any documented side effects of a particular drug observed in earlier clinical trials, you must ask for that information...

...which suggests that they might not tell you the exact side effects if you don't specifically ask them.


if you read a suggestion about informed consent by World Health Organization, they say that

Potential participants should be told if there are any known or anticipated side effects...

So, it depends whom you ask and what someone believes about what is good and what not.

I think if in previous trials no deaths or other side effects with permanent consequences or other severe side effects have occurred, it may be acceptable to not disclose them - if the participants are informed that they may occur, they agree with this, they believe it's good that they participate in the trial and they are in peace with this.

Or, as said here: Informed consent in clinical research: Revisiting few concepts and areas (PubMed, 2013):

How much or up to what extent the information should be provided on various aspects of research, such as risks and benefits associated with study intervention, is not clear and is rather a subjective approach depending on the investigator. For example, recounting or repetition of possible adverse effects of a study treatment may make that treatment ill-advised when the treatment is not that risky. On the contrary, if a lately appearing adverse effect is not disclosed to the patient, it raises question on the validity of the consent as the information was not provided adequately. Therefore, researchers are recommended to provide the study-related information adequately, judiciously, and truly maintaining an ethical balance between expected risks and benefits of the intervention under investigation.

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    Another angle, two really, is apart from investigator's opinion: what gets approved as ethical in a supervisional committee or judged so in a court. That already makes it implicitly clear that US has different standards for that than China. Jan 8 '19 at 13:33
  • so the bottom line here is that there is no consensus and standard?
    – Ooker
    Jan 8 '19 at 13:43
  • Yes, it seems so. It's something what a researcher and a participant need to resolve on a personal level.
    – Jan
    Jan 8 '19 at 13:49
  • I see. It seems that my question is more about lying, and it seems ethical if the research is a psychological one. What do you think about this? Especially on drugs that affect psychological state?
    – Ooker
    Jan 8 '19 at 14:12
  • If you ask me, lying about significant psychological effects or side effects could be unethical - but again, if the researchers honestly disclose that certain effects and side effects could happen (without specifying them) and if the participants accept that, it might be ethical. But then again, it's what exactly we are talking about. If the researcher is going to hypnotize you without you knowing this in an advance, it can be highly problematic.
    – Jan
    Jan 8 '19 at 14:17

At least for psychological study, it seem ethical to deliberately lying to the subjects, as long as the research is review through a committee about ethical issues. Source

In medical study, I think instead of saying affirmatively "we guarantee that there will be no side effect", they can say "this is a new drug so we don't know much about its side effect, but generally we think there is none". Plus I think they should say that it should be dizzy, so the subjects expect them to feel bad. The point is to let them expect that uneasy things will come, but not to let them expect the specific problem. This would still help them prepared.

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    This is more comment than answer. If you really want it to be an answer you need to provide supporting references.
    – Carey Gregory
    Jan 8 '19 at 15:43
  • yes, but I think the information is still useful to stand out from the comments
    – Ooker
    Jan 8 '19 at 16:30
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    It's not an answer. It's just a summary of your opinions.
    – Carey Gregory
    Jan 8 '19 at 16:49
  • @CareyGregory hmm, ok. Is it because it lacks reference? I see in other sites porting informative comments into answers is acceptable. I want to do this to clean up some comments above.
    – Ooker
    Jan 8 '19 at 17:37
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    Converting comments to answers is fine, but the answer still has to answer the question and have supporting references. Your second paragraph is mainly just an explanation of what you think and you offer nothing to say your opinions are correct.
    – Carey Gregory
    Jan 8 '19 at 20:15

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