The placebo effect

Like a magician’s illusion, the placebo effect has the power to turn something fake or inert into something real simply through belief that it is real. But what is the placebo effect? Placebo comes from the Latin, placere, meaning “I shall please.” It describes a real phenomenon where something inert, like a sugar pill, has a measurable, beneficial effect; whereas its harmful counterpart has been named the nocebo effect. There have been numerous studies investigating the neural mechanisms of the placebo effect (e.g., Benedetti et al 2011). Strictly speaking, this effect is not just “mind over matter” alteration of human health, but anything that produces a non-zero effect for an otherwise fake or sham treatment. There are three important causes that also count towards the placebo effect, including random chance, statistical biases and regression to the mean.

The first non-physiologic cause is random chance. By mere coincidence, the control group of an experiment, often a placebo control in clinical trials, may appear to have had a beneficial (placebo) or harmful (nocebo) effect. Researchers should be especially suspicious if the sample size in the experimental groups are small. The only thing guaranteed by taking s random sample is that the expected group effect, which should be none for the placebo, will approach this value with increasing sample size.

A second contributing factor is a social expectation bias. If a patient is sick, and they expect treatment, the patients expectations will rise and may exaggerate their symptoms and responses in favour of a successful treatment (or not). Therefore, a biased effect is measured.

The last and likely largest cause of the placebo effect is regression to the mean, more simply put as “symptoms fluctuate with disease.” Take patients suffering from chronic pain, in which some days are better than others. Patients measured on a worse day, reporting worse symptoms, are more likely to report improved symptoms on another day when the pain is likely to be closer to the average. Under this effect, pain may be improved/worsened simply by measuring it at two different times and regardless of treatment. More importantly, this phenomena occurs with any naturally fluctuating process, which makes it possible to observe in nearly all clinical trials. This last effect is also demonstrated in double blind placebo-controlled trials which have a non-treatment arm, in addition to the placebo and experimental arms. The effects measured in both the placebo and non-treatment arms are the same or similar.

The placebo effect, and it’s harmful counterpart nocebo, are real and measurable effects. There is interest in teasing out the molecular mechanisms behind such effects, but there are also causes for a spurious effect, including random effects, biases and regression to the mean.


Benedetti, Carlino, Pollo. How placebos change the patient’s brain. Neuropsychopharmacology (2011).

Some of my favourite Fall things

I think Mother Nature got confused about what season we’re in, because London got about 3 cm of snow this morning. While we are still (technically) in Fall, these are some of my favourite things to do on a Fall weekend.

Going for a hike around London, and especially around the Fanshawe Lake, is especially nice this time of year. The paths are mostly well marked, the leaves are a vibrant array of colours, and around dawn, the sun rising over the lake is very pretty. Together with Heather and the dogs, this is a nice picnic location, too.

If the weather outside is not so inviting, as it is this weekend, then I prefer to spend the mornings at home  sipping a large mug of coffee and reading a book. Nothing is more peaceful than having two tired dogs sleeping about and getting to enjoy a slow morning.

One of my favourite haunts is Wortley Village’s Black Walnut Café. It’s usually busy on the weekends, but they have great coffee and delicious pastries. It’s conveniently located near to a large park and on the multi-use trail system in London, so we can also go for a longer walk with the dogs after being reinvigorated by caffeine and sugar.

That’s all for now. If you would like to read more about the dogs, please have a read of our other blog, Digby’s Adventures in London.





Creating Videos on Video with OpenShot

Until recently, I have never really needed to create and compile videos on Linux, or any other platform. I knew that years ago, the landscape of video editors for Linux was dismal, and the platforms of choice were Mac first and then Windows.

Not knowing what to do, I googled my problem and found a list of possible solutions. I decided on OpenShot Video Editor because it aims to be a good balance between easy to use interface and supported using still images for video segments. This was appealing because I turned a Powerpoint presentation into a narrated video, and I all I had were sound recordings and still images of the slides.

Let me tell you, this thing did the trick, just as advertised. Without reading any manuals or searching for help, I was up and running in under two minutes. I dragged and dropped my content, then set up the video and audio clips on a timeline, set my output and then encoded a video. It was really quite painless and took me all of 15 minutes to create my presentation video from scratch.

If you ever need a relatively simple video editor, similar to Windows Movie Maker, then OpenShot Video Editor is a great choice for the Linux desktop environment.

Some problems with mandatory participation in the classroom

I recently began a Masters program in epidemiology and biostatistics. Many of my classes have mandatory participation built into the grading rubric. Teachers want to have active, and not passive, learners. Fair enough. As a former (and future) TA, I really like engaging with my students and getting the class excited and involved with the material. However, my view of some of these versions of participation exercises are, in my experience, not measuring the correct level of activity: active learning.

One classroom uses frequent student presentations, whereby students grade the content and delivery of the subject matter. Each student is given a minute to make a meaningful evaluation (only grades, no comments) on the presenter’s content and style. The large number of presentations rushes everyone in the class, and nobody wants to be “that person” who grades too harshly, so most (if not all) give inflated grades. The result is a class average of 95%+ and a meaningless marker of how the speakers improve or perform, and a classroom trained to reflexively waste their time to give an arbitrary grade. THIS IS BAD. I will offer one possible improvement on this structure, assuming the goal is to improve presentation quality. Adopt a simple criteria: did the speaker meet the content and delivery objectives? Yes or no, simple. Leave the student space to make constructive criticisms below, which are hard to formalize into a grade percentage. The speaker receives useful feedback that they can actively work on for the next presentation, and it is easy to screen that everyone has participated with their feedback.

Another criticism that I have involves the use of social media or polling software for the class. Sometimes, the polls are only possible by purchasing overpriced (and one-time-use-devices) “clickers”, and other times it uses a smart phone or web-based application. The appeal to the instructor is (perhaps) to calibrate whether the class understands a concept, and this can be very instructive for delivering lecture material. However, my experience has been that these technologies are reduced to the lowest common denominator: can you prove that you were in class, and that you were awake. If that’s the case, why bother using the technology when a simple roll call would suffice?

A common argument for the use of social media is that it promotes public discussion, either just with the class and the instructor, or the broader public community. This is possible, but I think in many cases, unlikely. For starters, those in the broader public (outside of the class) have no context for the discussion, and even if they did, I bet most people couldn’t be bothered or care enough to join in the conversation. Second, participation is often restricted to just the students in the class, so participation is probably better facilitated by an in-class discussion. Even those people that are too shy to make a comment out-loud have the option of privately giving the instructor comments or thoughts on the discussion, helping them to actively engage the content. My suggestion in this case is to have students instead write a short blog post to the teacher/class, or ask questions during the class to start discussions. The material is less likely to go ignored and unnoticed, and it might bring out more meaningful concepts to the class.

End of rant.