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DrugEpi 4-6 Weighing the Evidence Module 4 Overview Context Content Area: Interpretation of Epidemiological Evidence Essential Question (Generic): Is the.

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Presentation on theme: "DrugEpi 4-6 Weighing the Evidence Module 4 Overview Context Content Area: Interpretation of Epidemiological Evidence Essential Question (Generic): Is the."— Presentation transcript:

1 DrugEpi 4-6 Weighing the Evidence Module 4 Overview Context Content Area: Interpretation of Epidemiological Evidence Essential Question (Generic): Is the association causal? Essential Question (Drug Abuse Specific): Is an association with drug abuse causal? Enduring Epidemiological Understanding: Causation is only one explanation for finding an association between an exposure and a disease. Because observational studies are complicated by factors not controlled by the observer, other explanations must also be considered. Synopsis: In Module 4, students explore the rationale and methods of interpreting epidemiological studies. Students develop skills to assess possible explanations for an association found in a study, with consideration of explanations of causality, chance, confounding, reversed time order, and bias. Module 4 concludes with consideration of methods for weighing the overall evidence for an association. Lessons: Lesson 4-1: Introduction to Interpreting Associations Lesson 4-2: Causality Lesson 4-3: Chance Lesson 4-4: Bias Lesson 4-5: Confounding Lesson 4-6: Reverse Time Order Lesson 4-7: Weighing the Evidence

2 DrugEpi 4-6 Weighing the Evidence Module 4 - Interpretation of Epidemiological Evidence Lesson 4-6 Weighing the Evidence Content Description of a legal case involving a stillbirth and a mother who had used cocaine Consideration of the evidence for causality related to this case and of the role that public opinion can also play Big Ideas An association found in a single study or several studies with the same result should consider five possible explanations for an association, including causality, chance, bias, confounding, and reverse time order A judgment of causality may be made by considering several aspects of the strength and quality of an entire body of scientific evidence about an association This project is supported by a Science Education Drug Abuse Partnership Award, Grant Number 1R24DA , from the National Institute on Drug Abuse, National Institutes of Health.

3 DrugEpi 4-6 Weighing the Evidence Where are we? Essential QuestionsEnduring Understandings 1.How is this disease distributed? Health-related conditions and behaviors are not distributed uniformly in a population. They have unique distributions that can be described by how they are distributed in terms of person, place, and time. 2.What hypotheses might explain the distribution of disease? Clues for formulating hypotheses can be found by observing the way a health-related condition or behavior is distributed in a population. 3.Is there an association between the hypothesized cause and the disease? Causal hypotheses can be tested by observing exposures and diseases of people as they go about their daily lives. Information from these observational studies can be used to make and compare rates and identify associations. 4.Is the association causal? Causation is only one explanation for an association between an exposure and a disease. Because observational studies are complicated by factors not controlled by the observer, other explanations also must be considered. 5.What should be done when preventable causes of disease are found? Policy decisions are based on more than the scientific evidence. Because of competing values - social, economic, ethical, environmental, cultural, and political factors may also be considered.

4 DrugEpi 4-6 Weighing the Evidence McKnight Case “Regina McKnight is a 26-year-old native of Horry County, South Carolina. She has an IQ that, prior to trial, was measured at 72, i.e., “below average / borderline deficiency,” and attended special education classes in high school. She was unable to obtain a permanent job thereafter. Until 1998, Petitioner lived with her mother, who helped her with day-to-day needs. In 1998, however, Petitioner’s mother was killed by a hit and run driver. Left without the support system on which she had relied, she quickly spiraled downward, becoming homeless, addicted to both cocaine and marijuana – and pregnant. Lacking access to an adequate substance abuse treatment program, she was unable to overcome her drug dependence. (http://www.drugpolicy.org/docUploads/Petition_for_a_Writ_of_C ertiorari.pdf)

5 DrugEpi 4-6 Weighing the Evidence McKnight Case “On May 15, 1999, McKnight was transported, in labor, to Conway Hospital, where she delivered a stillborn girl. There had been no prior indication that the fetus was in distress, and it has never been suggested that McKnight intended to harm the fetus. On the contrary, the attending nurse testified at trial to having comforted McKnight, who was grief-stricken by the stillbirth. As is common with distraught parents, Petitioner asked to hold the stillborn baby and requested that photographs of the baby be taken. She told hospital staff of the name – “Mercedes” – that she had picked out for the baby. She asked to be given a “memory certificate” with the baby’s footprints and the bracelet that the baby had worn. She also asked to see the hospital’s chaplain. (http://www.drugpolicy.org/docUploads/Petition_for_a_Writ_of_ Certiorari.pdf)

6 DrugEpi 4-6 Weighing the Evidence McKnight Case “Within minutes of the stillbirth, however, hospital staff assumed a second role. Following a carefully developed “protocol,” they obtained a urine sample from McKnight, for drug testing. After that screen indicated that cocaine was present, a nurse, following the protocol, obtained McKnight’s signature on a form entitled “Informed Consent for Drug Testing,” and collected a second sample for “forensic” testing, with positive results reported to the State Department of Social Services (“DSS”). (http://www.drugpolicy.org/docUploads/Petition_for_a_Writ_of_ Certiorari.pdf)

7 DrugEpi 4-6 Weighing the Evidence McKnight Case “McKnight was arrested on October 7, 1999, and charged under a statute proscribing “homicide by child abuse,” S.C. Code § , which makes it a felony to “cause the death of a child under the age of eleven while committing child abuse or neglect,” if the death occurs “under circumstances manifesting an extreme indifference to human life.” The law provides for a prison sentence of twenty years to life. Id. § (C). (http://www.drugpolicy.org/docUploads/Petition_for_a_Writ_of_ Certiorari.pdf)

8 DrugEpi 4-6 Weighing the Evidence Background How Drugs Cross the Placenta

9 DrugEpi 4-6 Weighing the Evidence Cocaine Background

10 DrugEpi 4-6 Weighing the Evidence Stillbirth Background

11 DrugEpi 4-6 Weighing the Evidence Regina McKnight Background

12 DrugEpi 4-6 Weighing the Evidence Homicide by Child Abuse Regina McKnight McKnight Case

13 DrugEpi 4-6 Weighing the Evidence Beyond a Reasonable Doubt The burden of proof required by the prosecution in a criminal trial to obtain a guilty verdict. Demonstrating Causality

14 DrugEpi 4-6 Weighing the Evidence What do we mean when we say that there is an association between two things? Associated TiedRelated Linked Things that are associated are linked in some way that makes them turn up together. Review - Associations

15 DrugEpi 4-6 Weighing the Evidence Interpreting Associations versus Judging Causality On a study by study basis, we try to interpret associations by looking at possible explanations for those associations As a body of scientific knowledge accumulates, we consider all the evidence that is available and try to judge whether the weight of the evidence is sufficient to demonstrate a causal association. 1.Causal 2.Chance 3.Bias 4.Confounding 5.Reverse Time Order

16 DrugEpi 4-6 Weighing the Evidence Sir Austin Bradford Hill “The Environment and Disease: Association or Causation?” Proceedings of the Royal Society of Medicine January 14, 1965 Weighing the Evidence and Judging Causation Relevance to the McKnight Case

17 DrugEpi 4-6 Weighing the Evidence Sir Austin Bradford Hill “The Environment and Disease: Association or Causation?” Proceedings of the Royal Society of Medicine January 14, 1965 Explaining Associations and Judging Causation Relevance to the McKnight Case

18 DrugEpi 4-6 Weighing the Evidence “In what circumstances can we pass from this observed association to a verdict of causation?” Explaining Associations and Judging Causation

19 DrugEpi 4-6 Weighing the Evidence Causation: Epidemiological Versus Legal View January By Nancy A. Dreyer THE PROCESS of determining causation and, in fact, the ultimate need to determine causation is different in law and science. In law, the goal of fairness seems to be paramount. Decisions are required, no matter whether the true causes are known or understood. In contrast, scientists have been described as "practitioners of a discipline that seeks, but never finds, absolute truth" and as people who use a "variety of criteria to evaluate data in conditions that provide less than total certainty."(1) If lawyers and courts knew how epidemiologists look at causation and were aware of some of the methods used to provide scientific inferences, perhaps they would recognize the case for accepting the tentativeness of science and the scientific process. At a minimum, this knowledge would enhance their facility to make fair and equitable decisions. “An Epidemiological View of Causation: How it Deffers from the Legal” at defensejournal2.html Extension: Ask students to read this slide or pass as a handout.

20 DrugEpi 4-6 Weighing the Evidence “Here then are nine different viewpoints from all of which we should study association before we cry causation.” Explaining Associations and Judging Causation

21 DrugEpi 4-6 Weighing the Evidence Explaining Associations and Judging Causation 1.Strength 2.Consistency 3.Specificity 4.Temporality 5.Biological Gradient 6.Plausibility 7.Coherence 8.Experiment 9.Analogy Does the evidence support a verdict of causation?

22 DrugEpi 4-6 Weighing the Evidence Explaining Associations and Judging Causation 1.Strength What is the strength of the association between prenatal cocaine exposure and stillbirth? What is the strength of the association between the exposure and the outcome? Does the evidence support a verdict of causation?

23 DrugEpi 4-6 Weighing the Evidence Explaining Associations and Judging Causation 2. Consistency Has the association between prenatal cocaine exposure and stillbirth been found consistently by different researchers, in different places, using different study designs? Has the association between the exposure and the outcome been found consistently by different researchers, in different places, using different study designs? Does the evidence support a verdict of causation?

24 DrugEpi 4-6 Weighing the Evidence Explaining Associations and Judging Causation 3. Specificity Is prenatal cocaine exposure only associated with stillbirth or is it associated with other outcomes as well? Is the exposure only associated one outcome or is it associated with other outcomes as well? Does the evidence support a verdict of causation?

25 DrugEpi 4-6 Weighing the Evidence Explaining Associations and Judging Causation 4. Temporality Have studies established that prenatal cocaine exposure precedes the stillbirth? Have studies established that the exposure precedes the outcome? Does the evidence support a verdict of causation?

26 DrugEpi 4-6 Weighing the Evidence Explaining Associations and Judging Causation 5. Biological Gradient Has a biological gradient been demonstrated between prenatal cocaine exposure and stillbirth? Has a biological gradient been demonstrated between the exposure and the outcome? Does the evidence support a verdict of causation?

27 DrugEpi 4-6 Weighing the Evidence Explaining Associations and Judging Causation 6. Plausibility Is it biologically plausible that prenatal cocaine exposure could cause stillbirth? Is it biologically plausible that the exposure could cause the outcome? Does the evidence support a verdict of causation?

28 DrugEpi 4-6 Weighing the Evidence Explaining Associations and Judging Causation 7. Coherence Is the finding of an association between prenatal cocaine exposure and stillbirth coherent with our earlier knowledge? Is the finding of an association between the exposure and the outcome coherent with our earlier knowledge? Does the evidence support a verdict of causation?

29 DrugEpi 4-6 Weighing the Evidence Explaining Associations and Judging Causation 8. Experimental Is there experimental evidence, in which stillbirths have been produced by the prenatal administration of cocaine? Is there experimental evidence, in which the outcome have been produced by the administration of exposure? Does the evidence support a verdict of causation?

30 DrugEpi 4-6 Weighing the Evidence Explaining Associations and Judging Causation 9. Analogy Is the association between prenatal cocaine exposure and stillbirth analogous to another association between an exposure and an outcome ? Is the association between the exposure and the outcome analogous to another association between an exposure and an outcome ? Does the evidence support a verdict of causation?

31 DrugEpi 4-6 Weighing the Evidence Appeal Back to the McKnight Case

32 DrugEpi 4-6 Weighing the Evidence Amicus Curiae Friend of the Court Explaining Associations and Judging Causation

33 DrugEpi 4-6 Weighing the Evidence Amicus Curiae Friend of the Court Explaining Associations and Judging Causation

34 DrugEpi 4-6 Weighing the Evidence Amicus Curiae Friend of the Court Claim: Trial Counsel was ineffective for: failing to conduct an independent investigation that would have revealed readily accessible scientific information, evidence, and potential experts who could have testified regarding the etiology of stillbirths, the state of scientific knowledge regarding prenatal exposure to cocaine, and the nature of addiction. failing to adequately challenge the State’s case for causation which was based largely on misinformation, myth and prejudice, rather than scientific fact. failing to effectively cross examine the state's experts, and to call witnesses that were favorable to the defendant; Explaining Associations and Judging Causation

35 DrugEpi 4-6 Weighing the Evidence Explaining Associations and Judging Causation Read the friend-of-the-court brief. Identify the passages that address evidence for causality and the five possible explanations for an association. Identify the passages that address the five possible explanations. Categorize, according to Hill’s cause / effect questions, the scientific information, evidence, and expert testimony identified in the friends-of- the-court brief that they think are good arguments for: A prosecution team trying to uphold the conviction A defense team trying to reverse the verdict against Regina McKnight Assignment

36 DrugEpi 4-6 Weighing the Evidence END OF FIRST OF TWO CLASSES FOR Lesson 4.7

37 DrugEpi 4-6 Weighing the Evidence “It is important to note that each and every amicus curiae is committed to reducing potential drug-related harms at every reasonable opportunity. Thus, amici do not endorse the non-medical use of drugs – including alcohol or tobacco – during pregnancy, by either parent. Nor do amici contend that there are no health risks associated with cocaine (or other drug or alcohol) use during pregnancy. Nonetheless, it is entirely consistent with amici’s public health and ethical mandates to bring to this Court’s attention the medical and scientific information that is relevant to the case at hand.” Important Statement / Caveat

38 DrugEpi 4-6 Weighing the Evidence “… it is vital that convictions be based on valid scientific evidence rather than conjecture and misinformed popular opinion.” Main Argument: Importance of Science

39 DrugEpi 4-6 Weighing the Evidence “For nearly two decades before trial, the popular press was suffused with highly prejudicial and often inaccurate information about the effects of in utero cocaine exposure.” Influence of Popular Opinion

40 DrugEpi 4-6 Weighing the Evidence Science Versus Popular Opinion “… valid scientific evidence … (or) misinformed popular opinion.”

41 DrugEpi 4-6 Weighing the Evidence Science Versus Popular Opinion “… valid scientific evidence … (or) misinformed popular opinion.”

42 DrugEpi 4-6 Weighing the Evidence “… circumstantial case of guilt by simply producing evidence of a stillbirth, and the fact of cocaine use or any other unwise or unpopular behavior.” Influence of Circumstantial Evidence

43 DrugEpi 4-6 Weighing the Evidence Ingesting caffeine Gardening without gloves Changing a cat litter box Contact with anyone who is smoking Inhaling when handling household cleaning products Consuming unpasteurized cheese or undercooked meat Avoid … Precautions During Pregnancy

44 DrugEpi 4-6 Weighing the Evidence Deborah A. Frank et al., Growth, Development, and Behavior in Early Childhood Following Prenatal Cocaine Exposure: A Systematic Review, 285 JAMA 1613 (2001) A Weight of Evidence Review in JAMA

45 DrugEpi 4-6 Weighing the Evidence Three Criteria for Studies Included in JAMA Review Detailed review was … restricted to studies that … met three criteria: samples were prospectively recruited;1.

46 DrugEpi 4-6 Weighing the Evidence Three Criteria for Studies Included in JAMA Review Detailed review was … restricted to studies that … met three criteria: samples were prospectively recruited; examiners of the children were masked to their cocaine exposure status; 1. 2.

47 DrugEpi 4-6 Weighing the Evidence Three Criteria for Studies Included in JAMA Review Detailed review was … restricted to studies that … met three criteria: samples were prospectively recruited; examiners of the children were masked to their cocaine exposure status; the cocaine exposed cohort did not include a substantial proportion of children also exposed in utero to opiates, amphetamines, or phecyclidine, or whose mothers were known to be infected with the human immunodeficiency virus (HIV).”

48 DrugEpi 4-6 Weighing the Evidence Conclusions of 2001 JAMA Review Deborah A. Frank et al., Growth, Development, and Behavior in Early Childhood Following Prenatal Cocaine Exposure: A Systematic Review, 285 JAMA 1613 (2001)

49 DrugEpi 4-6 Weighing the Evidence The authors of Fetal Effects analyzed “all studies employing methodologies suitable for proving cause and effect relationships between cocaine and adverse pregnancy outcomes.” Another Study Cited in the Brief A Addis, ME Moretti, FA Syed, TR Einarson, G Koren Fetal effects of cocaine: An updated meta-analysis, Reproductive Toxicology 2001; 15(4): What is a meta-analysis? A technique for combining information from a number of studies in order to come up with a summarization of the findings

50 DrugEpi 4-6 Weighing the Evidence “Studies were excluded based on several criteria: because they were case reports, editorials, letters, reviews or commentaries, studies without fetal or pregnancy outcomes, in vitro studies or placenta profusion, studies with outcomes not within the scope of the meta-analysis, studies without a control group and studies where cocaine users had not been separated from users of other drugs.” Exclusions to Increase Rigor of Analysis

51 DrugEpi 4-6 Weighing the Evidence “Fetal effects …” reports the following comparisons: Comparing Cocaine Use to Other Drug Use ComparisonResult Poly-drug users versus non-drug usersEffect of poly-drug use Cocaine users versus users of drugs other than cocaine No difference This suggests that there are other factors associated with any drug use (not necessarily cocaine) that have a role in causing the adverse developmental fetal effects

52 DrugEpi 4-6 Weighing the Evidence Possible Confounders? ? Stillbirth or other developmental effect Cocaine or other drug use

53 DrugEpi 4-6 Weighing the Evidence “… it is the consensus of the medical community that the causes of stillbirth, to a large extent, are not fully understood. ‘In the United States, stillbirth accounts for a large proportion of all perinatal losses, although its causes remain incompletely understood.’ At least ten percent, but as many as fifty percent, of all stillbirths go entirely unexplained. As a recent article, summarizing research available before 2001, states: ‘In many cases it is difficult to be certain of the etiology of stillbirth. First, many cases are unexplained, despite intensive investigation of potential causes. Second, more than one condition may contribute to stillbirth in an individual case.’ Moreover, ‘it may not be possible to precisely determine which disorder was directly responsible for the loss. Indeed, it is likely that some cases of stillbirth are due to complications from multiple factors. Finally, conditions may be associated with stillbirth without directly causing them.’" Conclusions of Medical Community

54 DrugEpi 4-6 Weighing the Evidence “… it is the consensus of the medical community that the causes of stillbirth, to a large extent, are not fully understood. ‘In the United States, stillbirth accounts for a large proportion of all perinatal losses, although its causes remain incompletely understood.’ At least ten percent, but as many as fifty percent, of all stillbirths go entirely unexplained. As a recent article, summarizing research available before 2001, states: ‘In many cases it is difficult to be certain of the etiology of stillbirth. First, many cases are unexplained, despite intensive investigation of potential causes. Second, more than one condition may contribute to stillbirth in an individual case.’ Moreover, ‘it may not be possible to precisely determine which disorder was directly responsible for the loss. Indeed, it is likely that some cases of stillbirth are due to complications from multiple factors. Finally, conditions may be associated with stillbirth without directly causing them.’" Conclusions of Medical Community

55 DrugEpi 4-6 Weighing the Evidence “… it is the consensus of the medical community that the causes of stillbirth, to a large extent, are not fully understood. ‘In the United States, stillbirth accounts for a large proportion of all perinatal losses, although its causes remain incompletely understood.’ At least ten percent, but as many as fifty percent, of all stillbirths go entirely unexplained. As a recent article, summarizing research available before 2001, states: ‘In many cases it is difficult to be certain of the etiology of stillbirth. First, many cases are unexplained, despite intensive investigation of potential causes. Second, more than one condition may contribute to stillbirth in an individual case.’ Moreover, ‘it may not be possible to precisely determine which disorder was directly responsible for the loss. Indeed, it is likely that some cases of stillbirth are due to complications from multiple factors. Finally, conditions may be associated with stillbirth without directly causing them.’" Conclusions of Medical Community

56 DrugEpi 4-6 Weighing the Evidence “… it is the consensus of the medical community that the causes of stillbirth, to a large extent, are not fully understood. ‘In the United States, stillbirth accounts for a large proportion of all perinatal losses, although its causes remain incompletely understood.’ At least ten percent, but as many as fifty percent, of all stillbirths go entirely unexplained. As a recent article, summarizing research available before 2001, states: ‘In many cases it is difficult to be certain of the etiology of stillbirth. First, many cases are unexplained, despite intensive investigation of potential causes. Second, more than one condition may contribute to stillbirth in an individual case.’ Moreover, ‘it may not be possible to precisely determine which disorder was directly responsible for the loss. Indeed, it is likely that some cases of stillbirth are due to complications from multiple factors. Finally, conditions may be associated with stillbirth without directly causing them.’" Conclusions of Medical Community

57 DrugEpi 4-6 Weighing the Evidence “… it is the consensus of the medical community that the causes of stillbirth, to a large extent, are not fully understood. ‘In the United States, stillbirth accounts for a large proportion of all perinatal losses, although its causes remain incompletely understood.’ At least ten percent, but as many as fifty percent, of all stillbirths go entirely unexplained. As a recent article, summarizing research available before 2001, states: ‘In many cases it is difficult to be certain of the etiology of stillbirth. First, many cases are unexplained, despite intensive investigation of potential causes. Second, more than one condition may contribute to stillbirth in an individual case.’ Moreover, ‘it may not be possible to precisely determine which disorder was directly responsible for the loss. Indeed, it is likely that some cases of stillbirth are due to complications from multiple factors. Finally, conditions may be associated with stillbirth without directly causing them.’" Conclusions of Medical Community

58 DrugEpi 4-6 Weighing the Evidence “… it is the consensus of the medical community that the causes of stillbirth, to a large extent, are not fully understood. ‘In the United States, stillbirth accounts for a large proportion of all perinatal losses, although its causes remain incompletely understood.’ At least ten percent, but as many as fifty percent, of all stillbirths go entirely unexplained. As a recent article, summarizing research available before 2001, states: ‘In many cases it is difficult to be certain of the etiology of stillbirth. First, many cases are unexplained, despite intensive investigation of potential causes. Second, more than one condition may contribute to stillbirth in an individual case.’ Moreover, ‘it may not be possible to precisely determine which disorder was directly responsible for the loss. Indeed, it is likely that some cases of stillbirth are due to complications from multiple factors. Finally, conditions may be associated with stillbirth without directly causing them.’" Conclusions of Medical Community

59 DrugEpi 4-6 Weighing the Evidence Multi-Causality ”… it is scientifically inappropriate to declare fetal cocaine exposure to be the sole or even primary cause of fetal death.” Health Outcome C B A M L Z Y X

60 DrugEpi 4-6 Weighing the Evidence Multi-Causality “… stillbirth could have resulted from any variety of natural causes, including chorioamnionitis, funisitis, syphilis, meningitis, pneumonia, sepsis, and chromosomal abnormalities.” Health Outcome C B A M L Z Y X

61 DrugEpi 4-6 Weighing the Evidence Multi-Causality “… at the time of trial, there were extensive literature and studies establishing a wide variety of additional factors that were associated, in varying degrees, with stillbirth.” Health Outcome C B A M L Z Y X

62 DrugEpi 4-6 Weighing the Evidence Multi-Causality Trial Counsel failed to raise this host of alternative explanations that includes, but is not limited to, race and socioeconomic factors, hypertension, diabetes, thrombophilia, infections, maternal smoking, paternal smoking, paternal workplace exposure to ionizing radiation, exposure to pain medications and of course, poverty. Health Outcome C B A M L Z Y X

63 DrugEpi 4-6 Weighing the Evidence ? StillbirthCocaine Trial Counsel failed to raise this host of alternative explanations that includes, but is not limited to, race and socioeconomic factors, hypertension, diabetes, thrombophilia, infections, maternal smoking, paternal smoking, paternal workplace exposure to ionizing radiation, exposure to pain medications and of course, poverty. Explaining Associations and Judging Causation

64 DrugEpi 4-6 Weighing the Evidence ? StillbirthCocaine Many findings once thought to be specific findings of in utero cocaine exposure can be explained in whole or in part by other factors, including prenatal exposure to tobacco, marijuana, or alcohol and the quality of the child’s environment. Explaining Associations and Judging Causation

65 DrugEpi 4-6 Weighing the Evidence All scientific work is incomplete – whether it be observational or experimental. All scientific work is liable to be upset or modified by advancing knowledge. That does not confer upon us the freedom to ignore the knowledge we already have, or to postpone the action that it appears to demand at a given time. Explaining Associations and Judging Causation

66 DrugEpi 4-6 Weighing the Evidence Aftermath What has happened to Regina McKnight? The appeal was successful so a new trial was allowed. McKnight plead guilty to a lower charge (manslaughter) and was freed for sufficient sentence already served) She has three other children and said that she wanted to be with them again and that she had learned a lot about herself when she was in jail.

67 DrugEpi 4-6 Weighing the Evidence Explaining Associations and Judging Causation Send a Message Deterrent

68 DrugEpi 4-6 Weighing the Evidence Epidemiology... the study of the distribution and determinants of health-related states or events in specified populations and the application of this study to the control of health problems. Leon Gordis, Epidemiology, 3 rd Edition, Elsevier Saunders, Explaining Associations and Judging Causation

69 DrugEpi 4-6 Weighing the Evidence Explaining Associations and Judging Causation

70 DrugEpi 4-6 Weighing the Evidence Big Ideas in this Lesson (4-7) An association found in a single study or several studies with the same result should consider five possible explanations for an association, including causality, chance, bias, confounding, and reverse time order A judgment of causality may be made by considering several aspects of the strength and quality of an entire body of scientific evidence about an association This project is supported by a Science Education Drug Abuse Partnership Award, Grant Number 1R24DA , from the National Institute on Drug Abuse, National Institutes of Health. Re-Cap

71 DrugEpi 4-6 Weighing the Evidence Next Lesson Policy: Needle Exchange Programs


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