Causal Linkages (causal + linkage)

Distribution by Scientific Domains
Business, Economics, Finance and Accounting25%

Selected Abstracts

IS THERE A CAUSAL LINKAGE BETWEEN CANNABIS USE AND INCREASED RISKS OF PSYCHOTIC SYMPTOMS?

ADDICTION, Issue 8 2010
DAVID M. FERGUSSON
No abstract is available for this article. [source]

Alcohol and infectious diseases: an overlooked causal linkage?

ADDICTION, Issue 3 2009
CHARLES PARRY
No abstract is available for this article. [source]

Tests of causal linkages between cannabis use and psychotic symptoms

ADDICTION, Issue 3 2005
David M. Fergusson
ABSTRACT Aim To examine possible causal linkages between cannabis use and psychosis using data gathered over the course of a 25-year longitudinal study. Design A 25-year longitudinal study of the health, development and adjustment of a birth cohort of 1265 New Zealand children (635 males, 630 females). Setting The Christchurch Health and Development Study, a general community sample. Participants A total of 1055 participants from the Christchurch Health and Development Study (CHDS) cohort for whom data on cannabis use and psychotic symptoms were available on at least one occasion from 18, 21 and 25 years. Measurements As part of this study, data were gathered on frequency of cannabis use and psychotic symptoms at ages 18, 21 and 25 years. Findings Regression models adjusting for observed and non-observed confounding suggested that daily users of cannabis had rates of psychotic symptoms that were between 1.6 and 1.8 times higher (P < 0.001) than non-users of cannabis. Structural equation modelling suggested that these associations reflected the effects of cannabis use on symptom levels rather than the effects of symptom levels on cannabis use. Conclusions The results of the present study add to a growing body of evidence suggesting that regular cannabis use may increase risks of psychosis. The present study suggests that: (a) the association between cannabis use and psychotic symptoms is unlikely to be due to confounding factors; and (b) the direction of causality is from cannabis use to psychotic symptoms. [source]

Increasing accuracy of causal inference in experimental analyses of biodiversity

FUNCTIONAL ECOLOGY, Issue 6 2004
L. BENEDETTI-CECCHI
Summary 1Manipulative experiments are often used to identify causal linkages between biodiversity and productivity in terrestrial and aquatic habitats. 2Most studies have identified an effect of biodiversity, but their interpretation has stimulated considerable debate. The main difficulties lie in separating the effect of species richness from those due to changes in identity and relative density of species. 3Various experimental designs have been adopted to circumvent problems in the analysis of biodiversity. Here I show that these designs may not be able to maintain the probability of type I errors at the nominal level (, = 0·05) under a true null hypothesis of no effect of species richness, in the presence of effects of density and identity of species. 4Alternative designs have been proposed to discriminate unambiguously the effects of identity and density of species from those due to number of species. Simulations show that the proposed experiments may have increased capacity to control for type I errors when effects of density and identity of species are also present. These designs have enough flexibility to be useful in the experimental analysis of biodiversity in various assemblages and under a wide range of environmental conditions. [source]

Irreducibility and structural cointegrating relations: an application to the G-7 long-term interest rates

INTERNATIONAL JOURNAL OF FINANCE & ECONOMICS, Issue 2 2001
Marco R. Barassi
C32; C51 Abstract In this paper we examine the causal linkages between the G-7 long-term interest rates by using a new technique, which enables the researcher to analyse relations between a set of I(1) series without imposing any identification conditions based on economic theory. Specifically, we apply the so-called Extended Davidson's Methodology (EDM), which is based on the innovative concept of an irreducible cointegrating (IC) vector, defined as a subset of a cointegrating relation that does not have any cointegrated subsets. Ranking the irreducible vectors according to the criterion of minimum variance allows us to distinguish between structural and solved relations. The empirical results provide support for the hypothesis that larger, more stable economies can achieve policy objectives more successfully by accommodating rather than driving other countries' policies. It appears that the driving force is Canada, which is linked to the USA, UK and France in three out of the four fundamental relations, and which is a reference point for the US, Italian and German rates, which are not cointegrated, seem to be determined by country-specific factors. Copyright © 2001 John Wiley & Sons, Ltd. [source]

A review and new framework for instructional design practice variation research

PERFORMANCE IMPROVEMENT QUARTERLY, Issue 2 2010
Hillary N. Leigh MA
This article reviews practice variation in the field of instructional design. First, it compares instructional designer practice as reported or observed in several classic research studies. This analysis is framed by the standards established by the International Board for Training, Performance, and Instruction competencies for planning and analysis, design and development, implementation, and management. Although no certain causal linkages exist, we briefly review some of the reasons posited in the literature to explain instructional design practice variation (lack of time and resources, control in decision making, the designer's perception of a task, underlying philosophical beliefs, and designer expertise). Limitations of the literature base are explored, followed by a proposal for an alternative view of instructional design practice variation and recommendations. [source]

North atlantic oscillatiodannular mode: Two paradigms,one phenomenon

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 564 2000
John M. Wallace
Abstract The North Atlantic Oscillation (NAO), as defined in the studies of Sir Gilbert Walker ca. 1930, and the zonal-index cycle, as elaborated by investigators at the Massachusetts Institute of Technology some twenty years later, are different interpretations of the same entity, whose time variations are well represented by the leading principal component of the northern hemisphere sea-level pressure field. The NAO paradigm envisions this phenomenon as involving a unique teleconnection pattern in the Atlantic sector that varies on interannual and longer time-scales in association with large-scale atmosphere-ocean interaction. In contrast, the zonal-index-cycle paradigm posits the existence of independent, fundamentally zonally symmetric (or ,annular') modes of variability in the northern and southern hemispheres, both of which fluctuate on intraseasonal as well as interannual time-scales. Spontaneous interactions between the zonally symmetric flow and the eddies are viewed as being largely responsible for the variability of the annular modes at the higher frequencies, and a variety of different mechanisms including, but by no means limited to, atmosphere-ocean interaction are viewed as potentially capable of forcing them at the lower frequencies. The NAO and ,annular mode' paradigms offer contradictory interpretations of the causal linkages that are responsible for the observed correlations between North Atlantic climate variability and variations in a diverse array of zonally averaged quantities. They suggest different research agendas and they evoke quite different images in the popular press. It is argued that the two paradigms cannot be equally valid and that it is in the interests of the community to come to a consensus as to which of them is more appropriate. Rules of evidence are proposed as a basis for making that decision. [source]