Specific vs Non-Specific Effects, Where Do We Stand? | Modern Manual Therapy Blog - Manual Therapy, Videos, Neurodynamics, Podcasts, Research Reviews

Specific vs Non-Specific Effects, Where Do We Stand?

Specific versus Non-specific effects, where do we stand?

There has been some good discussion and debate in regards to specific and non-specific effects when it comes to treatment and outcomes with our patients. The pendulum can swing a lot between the perspective different people have on this topic. Alternatively, maybe, it is not a one or the other but a both that are not as easily distinguishable as two distinct concepts as we sometimes make it. Creating a definitional foundation on these two terms I think will be helpful as I try to unpack these two concepts.
Non-specific effects are often times referred to as placebo, which is technically incorrect. Placebo is a substance or treatment of no intended value such as a sugar pill.
First, let us talk about non-specific effects. Non-specific effects are often times referred to as placebo, which is technically incorrect. Placebo is a substance or treatment of no intended value such as a sugar pill. A placebo can produce non-specific effects which are the placebo or nocebo effects (placebo effects are the positive responses, nocebo effects are the negative responses) that occur within a treatment that are not attributed to the specific effects of the treatment. Most commonly, this is in reference to any effect a person might get from a treatment that is in the placebo control group. There are probably always multiple effects happening, thus the reason the plural term (non-specific effects) is used and not the singular form (non-specific effect). Some of the various effects that can be found are expectations, conditioned responses, reward systems, changes in emotional states, and others. Recognize that anytime someone is exposed to another person that is associated with treatment or any item that is related to an intervention it is impossible to not have non-specific effects enter into the context of the situation. While non-specific effects are labeled ‘non-specific’, recognize that we understand now there are specific neurobiological changes that occur during various placebo and nocebo effects. One may start to notice that our definition is starting to run into a bit of circle with non-specific effects having potential specific effects. Thus, I prefer the term contextual effects over non-specific effects, as these effects are based on the context the treatment is delivered in.

Therefore, with our definition of non-specific effects changed to contextual effects, let me move to specific effects definition. Specific effects are just the effects that are specific to the intervention. We recognize that drugs have specific effects on receptors in the body and thus they generate a response in a predictable fashion; or if we load a muscle through exercise, it responds in an expected way, sort of. Before I try to explain my “sort of” comment, let me remind everyone that many times we still do not fully recognize or understand all the various specific mechanisms that an effective therapy works through. One example would be opium, while it is a strong analgesic; all of its specific mechanisms it works through are still unknown at this time. So if they are unknown, then we can wonder how specific is it.

As I stated when it comes to drug and exercise the have known specific effects, they should respond in a specific fashion, but they do not respond perfectly the same every time. Thus why I stated ‘sort of’ in the previous paragraph. This is due to two primary reasons. First as I pointed out with something as opium and many of our interventions, we do not understand all the specific mechanisms involved as of yet. Thus, we cannot exactly predict all of the specific effects that occur. The other thing that makes the response to treatments with specific effects variable and always exactly the same is that contextual effects always enter into a treatment. Remember treatment is never delivered in a vacuum to a person that does not have any form of consciousness, thus non-specific (contextual) effects will enter into the equation.

The other thing that muddies the waters between labeling a treatment as having specific or non-specific effects is that it creates a notion that the two are exact opposites. The specific and non-specific effect debate if a treatment is one or the other is a bit erroneous. We know now it is not mind or body, it is both. It is not nature or nurture, it is both. It is not biological or psychological, it is both. We cannot separate them. A treatment such as a medication or exercise that are often referred to as interventions with specific effects, also have known non-specific effects. A treatment that is seen as only non-specific, energy crystal healing for example, does create specific effects within the brain and our neurobiology that we do not fully understand all the specific mechanisms that occur (not unlike opium). Therefore, for me, this labeling a treatment as one or the other is problematic.

What we do know is treatments will create an effect. Some treatments will have small to no effect, while others will produce a large effect. For good outcomes, picking treatments with consistent large effects is better than small to no effect. Some treatments have traditionally labeled specific effects we understand and some mechanisms in those specific effects we do not understand. We need to be honest and forthright with our patients what we do in regards to specific effects and mechanisms known and unknown. All treatments have traditionally labeled non-specific effects or what I prefer to call contextual effects. These can produce many different specific effects that have many interactions of which we do not fully understand the multiple mechanisms they work through.

There is debate on both sides in regards to studying the contextual effects, some say because they are so variable and to many interactions and not consistent that we should not study them and we should stick to just the specific effects. Others argue, that because all treatments have contextual effects we should understand them better so we can maximize them. I think debate over this topic is important as we continue to work toward unpacking what we do during our treatments and provide consistent language to explain and communicate our points. What say each of you? Where are you on the debate over specific and non-specific effects (contextual effects)?

via Dr. Kory Zimney, DPT
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