4.16: Causation
- Page ID
- 116202
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Let's take a moment to point out the difference between an association or correlation between two factors, and causation. We have said that a risk factor is something (a trait, a behavior, an exposure) that is associated with an increased probability of a disease or injury happening. While some risk factors are causes (for example, tobacco smoking is a risk factor for lung cancer AND tobacco causes lung cancer), many are not. For example, living in a rural area is a risk factor for car crashes -- but it isn't the cause of car crashes.
- Correlation means that the risk factor and the disease often appear together. It doesn't prove that one of them causes the other. There are at least three possibilities that could be true: if A and B occur together (correlation), then it may be that A leads to B, or B leads to A, or something else (let's call it C) leads to both A and B.
- Causation means that we have good evidence that A causes B. To establish causation of a disease, usually we need multiple studies over time that point in the same general direction. Randomized control trials are the "gold standard" for proving causation.
Optional video describing the difference between Correlation and Causation:
Some studies that ONLY show correlation get described in the press as showing causation, and not just in stories about health. I want you to think critically when you see the suggestion that A causes B.
A researcher by the name of Hill proposed a set of criteria for assessing causation. An association between a possible cause and a disease (or other health problem) doesn't have to meet every single one of Hill's criteria in order to be found to be truly causal. However, if the relationship is shown to meet most of Hill's criteria in most of the research studies that have been done, we can talk about causation with some confidence.
A researcher by the name of Hill proposed a set of criteria for assessing causation. An association between a possible cause and a disease (or other health problem) doesn't have to meet every single one of Hill's criteria in order to be found to be truly causal. However, if the relationship is shown to meet most of Hill's criteria in most of the research studies that have been done, we can talk about causation with some confidence.
These criteria are discussed in more detail on the next page on etiology and causation.
Keep in mind...
Sometimes a correlation is just random -- it doesn't mean anything. Take a look at these funny-but-true correlations. It is highly unlikely that any of them represent causation.
Of course, some unexpected correlations DO turn out to be causally related. New developments in science are often surprising. For example, there may be an association between lead in gasoline and rates of violence in the US -- it is being seriously considered by researchers of violence. We can use Hill's criteria to assess the strength of the argument for causation.