Simply put, the CHI score is an evidence-based rating system that shows degrees of confidence in cannabis as an effective treatment for a specific condition.
More specifically, the CHI score is a rating system that takes into account both the type of research study (which impacts the reliability of a study’s conclusions) and the study’s findings, which may be positively associated with medical use of cannabis (that is, the study reports that cannabis is a viable treatment) or negatively associated with it (the study says it doesn’t work).
Each experiment is scored based on type of study (between 1 and 5—see chart below), and then this number is multiplied by +1 if the study concluded that cannabis was effective, or multiplied by -1 if the study concluded that cannabis was ineffective. Studies with inconclusive or mixed results may be included in the text for your reference, but they do not contribute to the overall disease CHI score.
Finally, all the scores for individual studies included in the analysis of a disease are added together to create an overall disease CHI score. (An overall high disease score means that many studies have been conducted for this particular illness or that the studies conducted were of high caliber.) The overall CHI score is then divided by the total number of studies in each section ranging between 0 and 5 (or to a maximum of five leaf symbols), and this number is the CHI number that can be used to approximate degree of confidence about the current state of scientific inquiry for any particular disease listed.
While the CHI may not provide you with all the information that you need, the CHI can be an indispensable tool at your fingertips. Nevertheless, you may still want to discuss these studies with your health care practitioner. The CHI makes that possible, particularly if you have concerns about the effectiveness and/or safety of other methods available to you.
Importance of the Type of Research Study
Not all study types and designs, and their respective findings, translate equally well into practically useful insights. The scientific method informs and guides basic research and experiments. Different types of research studies attempt to test hypotheses—for example, that cannabis is an effective treatment for multiple sclerosis. Within medical research, double-blind, placebo-controlled, and clinical human trials provide the strongest evidence (that is, are deemed most likely to determine the truth). Next in line are controlled human trials. Studies that review and compare available published research are also highly respected, strong pieces of evidence. Less convincing, in order, are human case studies and case studies of individual clinical experiences, animal experiments, and laboratory studies. In this book, values are assigned to reviewed research studies that reflect the intrinsic strength of evidence associated with each type of study. The following chart gives the value assigned to each category at a glance.
Study Designs CHI Score Ratings
Double-blind, placebo-controlled, clinical human trials and double-blind,
placebo-controlled, clinical, crossover human trials +/– 5
Clinical human trials and cohort studies +/– 4
Reviews (of relevant literature and studies) and human case studies +/– 3
Animal studies +/– 2
Laboratory studies +/– 1
How Should I Use the CHI Score in General?
This book concentrates on diseases and conditions for which cannabis shows promise, so it should be no surprise that you will rarely see negative CHI scores. However, you may see negative as well as positive scores for individual studies if various studies reached different conclusions. Published studies were primarily extracted from MEDLINE, the U.S. National Library of Medicine’s bibliographic database. Inclusion criteria focused on the influence of the endocannabinoid system, cannabis and/ or cannabinoids on symptoms and diseases listed (A–Z) in the Cannabis Health Index.
Please note that a high total score reflects the amount of available published research to a much larger extent than it reflects the degree of efficacy of cannabis to treat the particular disease. The disease CHI score is a simple sum of all the individual study scores for that disease, so higher overall CHI numbers indicate that a large amount of research has been conducted for that disease.
How Should I Use the CHI Score for a Particular Study?
When comparing CHI values for one disease versus another, it is important to realize that the values are relative to the available academic literature. A lower value does not necessarily mean that cannabis is a less effective treatment. On the other hand, a higher CHI value does indicate not just a greater knowledge base but also a higher degree of scientific certainty that medical marijuana is beneficial for treating a specific disease (or disease group).
A CHI score of 3.5 to 5 for a particular study means that there is solid, actual evidence that cannabis may be a useful treatment. If it is relevant to your health issues, you may wish to share this citation with your doctor for his or her review.
A score of 1.5 to 3.4 for a particular study means that while more research needs to be done, it is probable that cannabis could be a useful treatment. While this is not conclusive evidence, you may still want to discuss these studies with your doctor, particularly if you have concerns about the effectiveness and/or safety of other methods available to you.
A score of 0 to 1.5 suggests that it is possible that cannabis is therapeutic or that study results were nonexistent, mixed, or inconclusive.
