Reading while wearing my therapist hat

Posts tagged ‘correlation’

Epidemiology, or Correlation Doesn’t Equal Causation

Johnson, Steven. (2006). The ghost map: The story of London’s most terrifying epidemic–and how it changed science, cities, and the modern world. Riverhead.

This readable, although occasionally repetitive, book describes the epidemiology used to track the source of cholera in 1854 London. The science of epidemiology was new, and the techniques the researchers used were new, too.  In fact, using these new techniques, the people involved manage to trace the transmission of a bacterial illness before bacteria themselves were known to science.

Ghost Map is well worth reading. Johnson intersperses background information—-such as the evolution of bacterial illnesses and the structure of 1850s London–with the story of how Dr. John Snow and Rev. Henry Whitehead found the source of the 1854 Broad Street epidemic.Original map made by John Snow in 1854. Choler... In describing these events, Johnson also uses well-chosen quotations from a wide range of Victorian sources, including medical journals, newspapers, and fiction. Snow and Whitehead’s research eventually led to the development of the modern sewer system in London.

I particularly noted Johnson’s account of how, when Snow and Whitehead published their findings, the medical establishment ridiculed them because they contradicted the prevailing “wisdom” about disease transmission. It reminded me of current events in both medicine and politics in which correlation is equated with causation or where people ignore current research because it doesn’t match their theory. Johnson’s analysis of this problem looks at many factors, such as the use of human senses in survival, the application of the scientific method, and the influence of published information on public opinion. Understanding this issue may help us to sort panic from science around current issues such as global warming, the “obesity epidemic”, and potential modern “plagues” such as bird flu.

Indeed, in the last few chapters, Johnson looks at the current issues of disease transmission, urban structure, and the possibility of modern epidemics. Unfortunately, despite the timeliness of this topic, I found this to be the most repetitive and least interesting section.

Overall, Johnson’s integration of information from so many varied sources makes Ghost Map an interesting look at an important part of scientific history that supplies useful insight into current issues.

P.S. For a humorous look at correlation vs. causation, see cartoon in Bloomberg Business Week.

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