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PubMed1982

Causal and preventive interdependence. Elementary principles.

"Synergism" of two factors in the causation or prevention of an all-or-none event means the existence of instances in which both factors are needed for the effect, while "antagonism" means that at least one can block the solo effect of the other. The manifestation of such interdependences--or of their complement, independence--in terms of event rates is complicated by the correlation of the susceptibilities to the two factors. Thus, given the risk difference (RD) values representing the solo effects, the RD corresponding to the joint exposure has a range consistent with independence so that independence cannot be inferred even from very ample data without knowledge of the degree of correlatedness of the susceptibilities. The definition of this range is closely analogous for causal and preventive factors, respectively. However, when knowledge about interdependence is used in inference about the factors' interrelation in the mechanisms for the effect, sharp distinctions may have to be made between causal and preventive factors. In each case, the interdependence is a result of the interrelation of the actions of the two factors and/or interaction between them. Operational decisions, having to do with the wisdom of the joint exposure, can be guided by knowledge about the interdependence of the factors; however, knowledge of the risks corresponding to the various exposures is a sufficient guide, without any need for inferences about causal or preventive interdependence.

Drug Antagonism↗

PubMed1994

Failure of doxycycline as a causal prophylactic agent against Plasmodium falciparum malaria in healthy nonimmune volunteers.

OBJECTIVE: To determine whether doxycycline, 100 mg administered as a single daily oral dose, is effective as a causal prophylactic agent, an agent active against the pre-erythrocytic liver stage of Plasmodium falciparum malaria parasites, in healthy nonimmune persons. If effective, the recommendation by the Centers for Disease Control and Prevention (CDC) that doxycycline be continued for 4 weeks after returning from malaria-endemic areas could be shortened to 1 week. DESIGN: Randomized, double-blind, placebo-controlled trial. SETTING: Medical ward at the U.S. Army Research Institute of Infectious Diseases, Fort Detrick, Maryland. PARTICIPANTS: 18 nonimmune, healthy, adult male volunteers, age 21.7 +/- 2.9 (SD) years, were enrolled in two groups, one of 8 persons and one of 10 persons. Six participants in the first group and 7 in the second group received doxycycline. The remaining participants received placebo. Two volunteers were dropped from the study, leaving 16 participants for analysis. INTERVENTION: Each participant received doxycycline, 100 mg, or placebo in a single daily oral dose starting 3 days before exposure to P. falciparum-infected mosquitoes and ending 6 days after exposure. MEASUREMENTS: Monitoring for parasitemia, plasma doxycycline concentrations, and mosquitoes' salivary-gland sporozoite grade. RESULTS: 6 of 6 (100% [95% Cl, 54% to 100%]) participants on doxycycline in the first group and 2 of 6 (33% [Cl, 4% to 78%]) in the second group were protected from malaria. No differences were found between protected and nonprotected participants in the doxycycline elimination half-life (T1/2) (20.8 +/- 5.0 h compared with 21.9 +/- 5.2 h), the steady-state average plasma concentration (1626 +/- 469 ng/mL compared with 1698 +/- 651 ng/mL), or other pharmacokinetic parameter estimates. The mean mosquito salivary-gland sporozoite grade was significantly higher (P = 0.02) in protected (3.5 +/- 0.3) than in nonprotected persons (3.1 +/- 0.1). Overall, 8 of 12 persons on doxycycline were protected from malaria, yielding a causal prophylactic efficacy rate of 67% (Cl, 35% to 90%). CONCLUSIONS: A dosing regimen of doxycycline, 100 mg once daily, administered as a causal prophylactic agent against P. falciparum malaria in healthy, nonimmune volunteers, had an unacceptably high failure rate. Therefore, the CDC recommendation that doxycycline should be taken daily starting 1 to 2 days before travel, during travel, and for 4 weeks after travel should still be followed.

Administration, Oral↗

PubMed1996

Tutorial: causal modeling and patient satisfaction.

Causal modeling is used in a variety of sciences because it allows exploration of complex relationships among several variables simultaneously. Although not used extensively in health care as yet, causal modeling could be helpful, given the complexity of the current health care system. The purpose of this article is to provide a general introduction to causal modeling and the syntax used in developing and testing a model. To illustrate the method, a sample model is tested using a combination of hypothetical and actual patient satisfaction data.

Data Interpretation, Statistical↗

PubMed2000

Causal authorship and the equality principle: a defence of the acts/omissions distinction in euthanasia.

This paper defends the acts/omissions distinction which underpins the present law on euthanasia, from various criticisms (including from within the judiciary itself), and aims to show that it is supported by fundamental principles. After rejecting arguments that deny the coherence and/or legal relevance of the distinction, the discussion proceeds to focus on the causal relationship between the doctor and the patient's death in each case. Although previous analyses, challenging the causal efficacy of omissions generally, are shown to be deficient, it is argued that in certain cases of causing death by omission the causal authorship of the doctor lapses. The final part of the paper examines why this should be morally significant and proposes an answer in terms of the principle of equality. Assuming all other factors are equal, the infringement of this principle provides an additional reason against actively killing a patient, which is not present in cases of passively letting die.

Authorship↗

PubMed2000

Causal authorship and the equality principle: a defence of the acts/omissions distinction in euthanasia.

Ethics↗

PubMedDate not supplied

[Causality, systems, and dynamic models. Three approaches of the explanation in demography].

The authors compare three methods of demographic analysis: "causal analysis, the transition models and the dynamic models. The purpose of these three approaches is not the same: transition models examine the transformation of a system during a given period; the dynamic model outlines the evolution of a social process through time; the causal analysis describes the mechanism through which the causes produce its effects. The three approaches differ also in the way they take time into account...[In particular,] causal static models are not pertinent in demographic research." (SUMMARY IN ENG)

Demography↗

PubMed1992

[Attributable risk percent under an effect modifier and legal causality].

Among civil trials there are cases which are influenced by evidence derived from epidemiologic studies. In such cases, causality of a factor (X) illegitimately introduced by defendants is considered to be measured with an epidemiologic measure, attributable risk percent (AR%) expressing the level of risk. This paper aims to discuss calculations and interpretations of AR% in complicated cases where plaintiffs themselves introduced an additional risk factor (Y) for the alleged health injury. When X is not an effect modifier, AR% of X adjusted for Y can be simply adopted for arriving at a judgement of causality. Where Y is an effect modifier, and is not an indispensable item in the plaintiffs' daily life (e.g., smoking), the AR% of X for those not exposed to Y and also the AR% for those exposed to Y may both need to exceed a legally determined threshold, in order for X to be legally acknowledged as being causal to the alleged injury. The role of epidemiologists for such trials is to determine the AR% of X for each level of Y, and to advise the court on a realistic range of the AR%s.

Effect Modifier, Epidemiologic↗

PubMed2005

The relationship between social anxiety and social support in adolescents: a test of competing causal models.

This study compared the strength of competing causal models in explaining the relationship between perceived support, enacted support, and social anxiety in adolescents. The social causation hypothesis postulates that social support causes social anxiety, whereas the social selection hypothesis postulates that social anxiety causes social support. The reciprocal model combines the two hypotheses by arguing that the causal relationship between social support and social anxiety is largely reciprocal. This study tests a modification of the reciprocal model by specifying perceptions of support as a mediating construct. Two waves of data with an interval of three months were collected on 357 college students. Structural equation modeling was used to compare the reciprocal and mediated reciprocal causal models. The study found some support for the mediated reciprocal model, but the magnitude of the relationships were weaker than expected. Limitations and suggestion for future research are discussed.

Adolescent↗

PubMed2005

[General contemplation on causality in appraising clinical efficacy of traditional Chinese medicine].

This paper briefly introduced the general principles for causality in scientific researches and clinical studies, addressed the importance of population-based approaches in it, and also reviewed the developing course and presented the elementary requirements of randomized controlled trials (RCTs). The author identified with views that as compared with the research design of other types, RCTs is the most authentic one in the aspect of causality of efficacy and intervention. It is stressed that a causal inference for the efficacy assessment of traditional Chinese medicine (TCM) must meet the nomothetic criteria. The author emphasized that the scientific merits of RCTs are not only for assessing the efficacy of conventional treatments, but also for TCM intervention owing to RCTs yield stronger inferences about therapeutic intervention than other study designs, which are wildly accepted by academic communities.

Evidence-Based Medicine↗

PubMedDate not supplied

[Causality in cardiology: concepts in evolution].

This paper describes several concepts about causality from Empedocles, Aristoteles and Galeno, to Koch and Hill and the evolution of these concepts related to cardiovascular diseases. Also defines cause and risk, and the philosophical theories about scientific knowledge: inductive versus refutation analysis. On these basis, the study of cardiovascular disease's causality, especially coronary heart disease, allows us the identification of several risk factors involved in its development. However, even with the presently coronary heart disease risk charts (from Framingham and European studies) the higher probability for the development of a cardiovascular ischemic event is around 40%, establishing an important degree of uncertainty. With the improvement in molecular biology techniques, genetics have attempted to analyse several genetic polymorphisms in search of the origin of coronary heart disease. Unfortunately, less than 10% of these polymorphisms have had a positive correlation with coronary heart disease being of minor risk that those obtained for having the diagnosis of type 2 diabetes mellitus or hypercholesterolemia. On these basis, the requirement of new population research projects in which clinical and genetic risk factors are to be studied for the appropriate understanding of the causality process of cardiovascular diseases must be a worldwide priority.

Cardiovascular Diseases↗

PubMed1991

Causal attributions, self-monitoring, and gender differences among four virginity status groups.

Sexual choices and behavior involve complex cognitive and affective processes. Attribution theory remains a prominent social-cognitive model that may help explain such phenomena. In the present study, 198 undergraduates, separated by self-reported virginity status, completed Russell's Causal Dimension Scale and Snyder's Self-Monitoring Scale. The purpose was to determine whether different virginity status groups make different causal attributions about virginity and sexual choices, whether self-monitoring influences this attribution process, and whether males and females differ in this regard. Results indicated a variety of statistically significant virginity status and gender differences in causal attributions. Self-monitoring, however, was not a significant covariate. Possible explanations for these results, and their implications, are discussed.

Adolescent↗

PubMed1991

Standardization of definitions and criteria of causality assessment of adverse drug reactions. Drug-induced cytopenia.

International reporting of adverse drug reactions to pharmaceutical manufacturers or authorities requires internationally accepted standard definitions of reactions and criteria for assessment of causality. Under CIOMS (Council for International Organizations of Medical Sciences) auspices, an international meeting organized by Roussel Uclaf pharmaceutical company in Paris in 1989 agreed on a series of standard designations of drug-induced liver disorders and criteria of causality assessment. The second such international meeting, on drug-induced cytopenia, held in Paris in April 1990, resulted in a series of proposed standard designations of the various forms of drug-induced cytopenia and criteria of causality assessment in respect of neutropenia, thrombocytopenia and aplastic anemia.

Agranulocytosis↗

PubMed1990

Menière's symptoms resulting from bilateral otosclerotic occlusion of the endolymphatic duct: an analysis of a causal relationship between otosclerosis and Menière's disease.

An association between otosclerosis and Menière's disease has been proposed on both a clinical and temporal bone histopathologic basis for well over three-quarters of a century. Controversy persists over a causal relationship between these two entities, however, and the underlying pathophysiologic mechanisms relating capsular otosclerosis with Menière's disease remain speculative. The first case of total, bilateral endolymphatic duct occlusion resulting from extensive capsular otosclerosis is presented in a woman manifesting Menière's symptoms. The severe endolymphatic hydrops resulting from otosclerotic endolymphatic duct occlusion is given as histopathologic proof of a causal relationship between these two entities. Analysis of 18 of our own temporal bone cases of extensive capsular otosclerosis without endolymphatic hydrops and review of the literature indicates the uniqueness of such a firm causal relationship in the present case.

Adult↗

PubMed1989

Causal explanations and emotional health of women during divorce.

This study investigated (a) relationships between women's causal explanations for divorce and their present emotional health, and (b) the clinical usefulness of the Personal Stress Inventory (Ireton, 1980) as a stress assessment tool. The convenience sample consisted of 36 women ending a first marriage. Subjects were interviewed using the Tennessee Self-Concept Scale (Fitts, 1965), the Personal Stress Inventory, and a causal explanations questionnaire. Results indicated that causal explanations did predict self-esteem and emotional distress under conditions suggested by the reformulated learned helplessness model. The Personal Stress Inventory includes an emotional distress subscale that predicted self-esteem, self-perceptions of coping ability, and overall concerns about wellness/energy.

Adaptation, Psychological↗

PubMed1989

Concepts of potency and resistance in causal prediction.

This study examined the development of causal prediction using physical systems with effects of continuous magnitude. Accurately predicting the magnitude of an effect (ME) requires integration of information about the potency (P) of the causal agent and the resistance (R) of the effect. 10 5-year-olds, 10 9-year-olds, and 10 adults each viewed 36 instances of each of 2 causal mechanisms in which 6 levels of P were crossed with 6 levels of R. For every (P, R) pair, subjects were asked to predict ME. For one mechanism (the balance), an accurate combination of P and R would correspond to a subtraction model (ME = P-R), whereas for the other mechanism (the ramp), a division model (ME = P/R) would yield accurate predictions. Subjects' theoretical models of the roles of P and R were inferred from (a) correlations of their predictions with ideal answers, (b) multiple regression analyses, and (c) analysis of the number of categories P and R that each subject employed. Relative to older subjects, 5-year-olds treated P and R as having fewer categories of intensity. Although 5-year-olds did not generally achieve high correlations with ideal answers, many systematically used P and/or R to influence their predictions. Subjects used P and R more systematically on the balance problem than on the ramp problem. 9-year-olds employed the correct model (subtraction) on the balance problem but applied the subtraction model to the ramp problem as well. Adults converged on the correct models for each mechanism. The results are interpreted in terms of the progressive refinement of a rough, qualitative theory.

Attention↗

PubMed1989

Can the causal model approach contribute to the study of the epidemiology and the control of sleeping sickness?

A causal model links together, in an hierarchical manner, a set of hypotheses about the causes of, and mechanisms leading to, a phenomenon under study. Initially used in nutrition studies for identifying the variables to be observed, such models have proven useful in the choice and evaluation of interventions, as well as in the selection of relevant special studies to be carried out inside a broader research programme. The authors describe a technique of model building used by nutritionists, and argue that this approach could be of benefit in the study and control of african trypanosomiasis. Their hypothesis is that although causal models do not substitute for mathematical models, the latter ones, and epidemiological models in general, would be (1) more correct logically; (2) fitting reality more closely; and (3) more useful for the analyst, the decision maker and the field worker, if they were built from an preceding causal model.

Humans↗

PubMed1988

A causal link between handwashing and risk of infection? Examination of the evidence.

To examine evidence of a causal link between handwashing and risk of infection, a review of published literature from 1879 through 1986 was conducted. In the 107 years studied, 423 articles specifically related to handwashing were found. Articles were categorized as studies to evaluate products (50.8%), review articles (29.1%), behavioral studies (10.9%), methodologic studies (2.8%), studies linking handwashing to infection (3.3%), and other (3.1%). There was an increase in the proportion of handwashing articles published in the 1980s with the rate (9.4/10(5) citations/year) being almost double that of any other period studied. Nonexperimental and experimental studies related to handwashing were reviewed and evidence for a causal association evaluated. Except for specificity, all the elements for causality, including temporality, strength, plausibility, consistency of the association, and dose response were present. It was therefore concluded that emphasis on handwashing as a primary infection control measure has not been misplaced and should continue.

Communicable Disease Control↗

PubMedDate not supplied

[Representations of causality and depression. A factorial approach to the resignation model in the depressed patient].

The present study investigates causal attributions for stressful life events within the context of Beck's cognitive theory of affective disorders and Seligman's learned helplessness model of depression. The aim was to assess the validity of the depressive attributional style proposed by Seligman, with a clinically depressed population for negative life events. This study presents a factor analysis of the causal attributions of depressed psychiatric in patients measured in relation to one negative life event per subject. The experimental procedure consisted in asking 71 ward depressed patients (51 females and 20 males) to answer 15 items along a seven point scale in order to assess the causes, consequences and control attributed. Statistical treatment using both multidimensional analyses (to describe the dimensions of causality) and univariate comparisons show: 1. The existence of a three dimensional solution, which is interpreted in terms of Seligman's reformulated helplessness model, and which confirms the notion of a "depressive attributional style". 2. A positive relationship between intensity of depression and the tendency to generalize the effects of negative life events (dimension of globality in Seligman's model and generalizability in Beck's). As this relationship is a function of the level of depression it is considered as a psychological state rather than as a personality trait. 3. Inter-sex differences with regard to the attribution of personal versus universal control, with female patients indicating more personal helplessness in relation to others. The results are discussed in relation to epidemiological data and personality theory.

Adult↗