For those of you new in the field of genetic testing, you must first have a solid understanding of correlation versus causality. The distinction between these scientific terms can allow you to make the most of your genetic tests and really understand how your genes affect your health and lifestyle. While the two terms are related, the difference between correlation and causality is similar to the difference between an educated guess and knowing the answer directly.

Knowing if a genetic report is based on correlation or causality makes a big difference in how serious the results should be (or how good the test kit is).

First, let us understand what correlation and causality they really are.


A correlation is a relationship between two elements. These relationships can be simple. For example, if the number of bees increases, so will the number of fruit produced. This statement is correlated because it relates a number to another number, without saying exactly why the two entities are related.

Correlations are usually found only through statistics. Correlations provide scientists with an opportunity to understand what factors may be influencing the outcome of a given situation. In the case of genetics, many genes are correlated with specific results. A certain gene may be related to an increase in heart disease. This is a correlation, but it tells you nothing about why the gene variant can increase heart disease. Moreover, many correlations are false because they do not predict causality.


The cause, on the other hand, is much more powerful and insightful. If scientists can prove causality between two events, it means they can show directly how one trait or event led to the other. With the example of bees and fruit, causality would show that an increase in bees leads to an increase in pollination events, which eventually increases the amount of fruit produced by a tree.

Finding the causality of an event or outcome is much more difficult. Not only must scientists prove that two events are related, but they must also show exactly how the first event leads to the second. With genetic testing, causality is fully understood in only a small number of traits, such as the ability to taste bitterness in certain vegetables.

This bitterness is caused by the presence of a single protein within the taste buds. If you have the gene for this protein, it will be expressed in your tongue and you can test when these bitter compounds enter your mouth. Without the gene, you can’t test bitter substances. This shows causality because not only does it relate the variant of the gene to the trait, but it describes exactly how the presence of the gene results in proving bitterness in Brussels sprouts.

Correlation Vs. Causation

Correlation Vs. Causation

The cause is a much more powerful tool for scientists, compared to the correlation. The correlation only shows that two things are linked. The cause goes one step further and explains why things are linked and how one thing causes another.

The problem with using only correlation is that sometimes correlations can be misleading. Correlations can be found among most things.

Correlation, Causation and Genetic Testing

When it comes to genetic testing, you should be very careful to understand whether the report you get details the correlation or causality. Most genetic tests, unfortunately, only look at causality. Let’s look at some different examples of genetic test results.

Single Gene Traits

Unique genetic traits are almost always understood to the level of causality. Not only is there a link between the variants of these genes and the physical result, but scientists have described in detail how these variants lead to the physical result.

A good example of causality within the Traits of a single gene is its blood type. Your blood type is A, B, AB U or, depending on the genetic variants you inherited from your parents. These genes, in turn, produce a series of proteins and antibodies present in your body. These proteins and antibodies recognize each other and ensure that no external cells like bacteria can invade your system.

If you carry the genetic variant for Type A antigens, you have Type A blood. carriers of only the B antigen gene have Type B blood. some people have variants of A and B antigens, giving them type AB blood. A fourth type of blood, or, is created when a person does not carry genetic variants to create antigens A or B. Therefore, the blood type is fully determined by the genetics of a person and we have the molecular understanding to demonstrate exactly how this process occurs.

Unique genetic traits are the most likely to show causality between the gene and trait because they are the simplest form of a trait to study. If only 1 allele is affecting a trait, it is easy to study the genetic variant and find out how a gene works at the molecular level to produce the trait in a person.

Polygenic Features

Unfortunately for genetic testing, most traits are not determined by a single gene or allele. In fact, most traits are polygenic, which means they are affected by several genes at the same time. With these traits, causality is more difficult to show because of the complex interactions between genes and their environment.

Polygenic Features

While causality can be shown in polygenic traits, it is much more difficult to do so. In fact, to show causality in a polygenic trait, researchers must first understand the product of each gene involved. They must then map and describe how genes relate to each other to produce a certain trait. This is a very intensive and complex process, which is very expensive to complete.

On the other hand, it is relatively easy and cheap to determine a correlation between any number of genes and a trait. The problem with this method is that certain genes can play no role in a trait, but they are simply present in people with the trait. If you have one of these genetic variants, a report based on correlations can show that you have a certain trait when you really don’t. In fact, many genetic tests are based solely on correlation studies and reporting companies have no idea how the gene actually works in their body.

Now, let’s look at various types of genetic testing and see if they’re using correlations or causations.

Correlation or causality?

Tests for unique genetic traits

Genetic testing for single gene traits is often the most reliable. Genetic testing, in general, is extremely accurate in identifying genetic variants and sequencing their genome. Almost any genetic test for traits like the blood type will be accurate and will describe it exactly. These traits are not only correlated with variants of the gene, but a direct causality has been established between having a genetic variant and showing a given trait.

Genetic Ancestry Tests

When it comes to tests of genetic ancestry (such as Descent, 23andme or myheritage) we are not really discussing correlation or causality. In fact, genetic testing works on a much simpler concept. Genes have to come from somewhere. Furthermore, because mutations occur slowly over time and are extremely rare, the vast majority of their DNA comes directly from their ancestors.

Genetic ancestry tests simply analyze their DNA and then compare it to reference populations around the world. This may give you an idea of where your genes originated, as they are often still present in the population from which your family originally came. However, these tests usually ignore the fact that you only receive half of your parents ‘ combined genetics. Like you, your parents only received half of your parents ‘ combined genetics.

In practice, this means that only the genes present in your body will be related to reference populations, although your real family may be much larger. Genetic ancestry tests are a good tool to analyze parts of your family history, but they can only report on the genetic variants actually present within your body.

Genetic Disease Testing

Disease risk traits are often where genetic testing companies begin to take some liberties with their reports. With hundreds, or possibly thousands of genetic reports published every year, there are endless correlations between genetics and disease.

Unfortunately, few or none of these diseases are completely caused by genetics. More than that, almost none of the increases in risk has been explored deep enough to understand how a particular variant can increase your risk of disease.

A good example is the BRCA, that are known to be correlated with breast cancer. The FDA has approved tests for the BRCA gene because it has been shown how a mutated BRCA gene can cause cancer. Therefore, some causality has been shown for BRCA genes and cancer. However, only a small portion of all breast cancer is caused by mutant BRCA genes, so even this test is not very informative. Most genes related to disease risk are related only through correlation, which can be completely random until proven otherwise.

Polygenic Trait Tests

Some companies offer genetic testing for things like” intelligence “or”depression.” While there have been correlations between genetics and these complex issues, no one has shown any causality. In fact, due to the large number of genes involved in these traits and the impact of the environment on the formation of traits, genetic testing is unlikely to contribute significantly to understanding these traits.

Like the use of margarine and Maine’s divorce rate, some complex features are certainly correlated with several genotypes. However, this does not provide evidence that one is affecting the other. Of all the traits that analyze genetic reports, these are the least likely to be useful. In fact, complex topics such as cognition and learning stand out, which are more related to their environment than to their genetics.

Other Types of Genetic Testing

Other genetic tests available include nutrition, pharmacogenomics, or fitness traits. Like any polygenic trait, these are largely only correlations and no solid causality has been identified. A large number of new companies are emerging to inform you about these correlations. But don’t buy yet, these correlations will probably be largely cancelled out and refined over the next few years. Read on to see some of the companies currently focused on correlation, rather than causality.

Microbiome Tests

A new branch of DNA testing is microbial testing. This test analyzes the individual profile of each person of bacteria, archaea, viruses that inhabit his or her body and attempts through sophisticated analytical tools and AI to correlate between the profile of one and certain diseases and conditions. It is still difficult to say whether this can be considered simple correlation or that this field will grow indefinitely (some experts even claim that it will pass DNA testing because the information provided is more complete).

Companies that Rely on Correlation

That We Wouldn’t Recommend Using

While most large DNA testing companies (think 23andMe or Ancestry) work with traits that are usually explained to the exact molecular cause, or at least supported by a large number of correlation studies, there are many smaller emerging companies that do not meet these standards. Below are several of these companies, and the evidence they offer that is based solely on correlation, not causality (in many cases these are DNA data testing companies that only process the external data provided to them).


This company focuses on skin care, and the company has recently adopted a DNA approach to determine appropriate medications and lotions for your skin’s health. While this may sound intriguing, there are several science-related warning signs behind his “miraculous healing of DNA skin.” In fact, if you go to your science page behind your products, you will find that they are basing your entire DNA business model on only 2 peer-reviewed items, and less than 1000 DNA tests.

As for the correlation on causality, Allél relies only on a minor correlation. While there is other evidence supporting some of your products and procedures, there is no way that just 2 documents and 800 people can provide a complete understanding of how DNA affects your skin. In fact, most of the skin conditions they are fixing can be seen directly, and there is no need to test a person’S DNA to fix their condition. The DNA test appears to be just another sales tactic aimed at reaching the new “DNA test”market. Unfortunately, many people will be bound by this” science ” and buy their supplements, lotions and other products. The products can work, but it won’t be because they specifically fit your DNA.

Genomelink Link

For free, Genomelink will provide you with a more detailed analysis of your DNA than any of the leading companies will give you. While this is interesting information for a great price, you should know that most of the reports you give are based solely on the correlations between a trait and certain genetic variants. Few of the features that report on are based on more correlations.

For example, Genomelink has a report on child intelligence. Several studies have found correlations between certain genes and the general intelligence of childhood. Genomelink presents this information as if the genes were certainly responsible for the increase in intelligence. However, we also know that child intelligence is malleable and largely affected by a child’s environment. Without showing causality, it could easily happen that certain populations have better learning and study habits, which in turn leads to greater intelligence.

The Japanese, for example, share many genetic variants, as well as a culture that supports and improves child intelligence. So, it’s kind of like chicken and egg. Did genetic variants cause greater intelligence, or were variants simply present as culture developed advanced teaching methods? Until causality is shown, we’ll never know.


Like Genomelink, Promethease shows you many studies based on the genetic variants you have. It also allows you to explore your genome and gives you access to a series of reports for only $ 12. While this is also a decent price, most of the studies it presents are only correlations. But, you can easily save $ 12 by looking for studies yourself, in SNPedia. This wiki site is constantly updated with the latest genetic studies, ordered by genes. However, unlike many of the other companies listed here, Promethease is simply connecting you with scientific studies, so you can determine the correlation and causality yourself.


Lifenome focuses on traits such as nutrition, fitness, skin care, allergies, and personality. Unfortunately, none of these traits have been shown to be caused by a single gene. In fact, all these traits are highly polygenic traits and are deeply influenced by their surroundings. It is a very complex issue, and many genetic variants have correlated with various aspects of nutrition and fitness.

To avoid this complexity, companies such as Lifenome simply report which variants it has and whether those variants have been involved in any correlation study. The company claims to be using artificial intelligence to determine which correlations are significant, although this technology has never been shown to find anything but correlations. So, in effect, they’re selling you their “best guess” about how your genetics can affect your life.


The Habit company focuses solely on nutrition and genetics, stating that it can produce the “ideal” diet for its “genetic type”. Unfortunately, the science behind diet and genetics isn’t that advanced yet. Many different genetic variants have been correlated with various aspects of nutrition, such as the ability to digest carbohydrates or the ability of your body to absorb a specific vitamin. However, most of these studies are simple correlations and really tell you nothing about the chemistry of your specific body.

More than that, the whole idea that diets should be “specialized” for the individual is largely pseudoscience. In fact, epidemiologists have shown that a plant-based Whole-Food Diet is probably the most beneficial for all people, regardless of their genetic variants, heritage or culture. Companies like Habit greatly promote a general healthy diet under the guise that they are customizing a diet “specifically for you.” Starting at $ 200, these reports are largely a waste of your money.


As a Habit, DNAFit focuses on an area of genetics: fitness. Also as a Habit, the science behind these reports is largely in the form of correlation studies. The company has taken small aspects of general fitness, such as muscle composition or aerobic capacity, and has linked each aspect to genetics. While these components are partially determined by genetics, there is also ample evidence that these traits are highly variable depending on a person’s number of exercises.

For example, your genetic fitness report may show that you would be a better resistance corridor, depending on the type of muscle your genes are most likely to reproduce. But other studies have shown that the more a person runs, the more their muscles will adapt to that activity. Similarly, the oxygen capacity of the blood can be easily increased by working on elevation and forcing your body to produce more blood cells. Therefore, the correlations provided by companies such as DNAFit are largely useless. Considering you’ll pay $ 150 for these results, you better hire a personal trainer and just work on the things you want to be better at.

DNA Romance

The latest and most egregious use of genetic correlations is found in companies such as DNA Romance. DNA Romance does exactly what its name implies: it matches users according to their”genetic compatibility”. The entire company is based on only 20 + studies that broadly correlate the production of pheromones to compatibility quotes. The whole premise behind the enterprise drastically underestimates and simplifies human attraction and love. Both issues are complex and involve early childhood, family structure, and past experiences. Your genetics probably play a role, but how big of a role has not yet been determined.

Other Tests to Consider

This is not an exhaustive list of genetic testing companies. There are companies that will give you wine selections based on your genetics, and other similar nonsense. While these tests may be a fun way to try new wines, science is limited to correlations that only a few laboratories have found. In the future, with much more research, we can begin to find causality behind some of these correlations. But, until then, these companies are simply charging you to get generalised advice based on the fact that a certain gene might be related to your tastes and preferences. Like learning, memory, and quotes, these traits can easily be changed based simply on what you do every day and the new things you try.


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