Terms such as risk, risk factors, and especially the term cause are inconsistently and imprecisely used, fostering scientific miscommunication and misleading research and policy. Clarifying such terms is the essential first step. We define risk and a risk factor (protective factor) and their potency, set out the conceptual basis of the methods by which risk factors are identified and potency demonstrated, and propose criteria for establishing the status of a risk factor as a fixed or variable marker or a causal risk factor. All definitions are based on the state of scientific knowledge (empirical documentation), rather than on hypotheses, speculations, or beliefs. We discuss common approaches and pitfalls and give a psychiatric research example. Imprecise reports can impede the search for understanding the cause and course of any disease and also may be a basis of inadequate clinical or policy decision-making. The issues in risk research are much too important to tolerate less than precise terminology or the less than rigorous research reporting that results from imprecise and inconsistent terminology.

Classifying putative risk factors into these qualitatively different types can help identify high-risk individuals in need of preventive interventions and can help inform the content of such interventions. These methods may also help bridge the gaps between theory, the basic and clinical sciences, and clinical and policy applications and thus aid the search for early diagnoses and for highly effective preventive and treatment interventions.

Absence of a common diagnostic interview has hampered cross-national syntheses of epidemiological evidence on major depressive episodes (MDE). Community epidemiological surveys using the World Health Organization Composite International Diagnostic Interview administered face-to-face were carried out in 10 countries in North America (Canada and the US), Latin America (Brazil, Chile, and Mexico), Europe (Czech Republic, Germany, the Netherlands, and Turkey), and Asia (Japan). The total sample size was more than 37,000. Lifetime prevalence estimates of hierarchy-free DSM-III-R/DSM-IV MDE varied widely, from 3% in Japan to 16.9% in the US, with the majority in the range of 8% to 12%. The 12-month/lifetime prevalence ratio was in the range 40% to 55%, the 30-day/12-month prevalence ratio in the range 45% to 65%, and median age of onset in the range 20 to 25 in most countries. Consistent socio-demographic correlates included being female and unmarried. Respondents in recent cohorts reported higher lifetime prevalence, but lower persistence than those in earlier cohorts. Major depressive episodes were found to be strongly co-morbid with, and temporally secondary to, anxiety disorders in all countries, with primary panic and generalized anxiety disorders the most powerful predictors of the first onset of secondary MDE. Major depressive episodes are a commonly occurring disorder that usually has a chronic-intermittent course. Effectiveness trials are needed to evaluate the impact of early detection and treatment on the course of MDE as well as to evaluate whether timely treatment of primary anxiety disorders would reduce the subsequent onset, persistence, and severity of secondary MDE.

The reliability and validity of the 12-item General Functioning (GF) subscale of the McMaster Family Assessment Device (FAD) is reported here. Psychometric properties of the FAD have been previously determined, but no independent assessment has been made of the GF subscale, which was used to measure family functioning in the Ontario Child Health Study (OCHS). Reliability was measured by Chronbach's alpha and split-half correlation. Validity was assessed by hypothesizing the relationships expected between the GF scores and other family variables included in the OCHS data set. The results indicate good reliability, and all hypotheses of validity were supported. The brevity and ease of administering the GF subscale recommend it for further use in survey research in which a global assessment of family functioning is required.

The Early Development Instrument (EDI), a teacher-completed measure of children's school readiness at entry to Grade 1, was designed to provide communities with an informative, inexpensive and psychometrically sound tool to assess outcomes of early development as reflected in children's school readiness. Its psychometric properties at individual level were evaluated in two studies. Five a priori domains -physical health and well-being, social competence, emotional maturity, language and communication, and cognitive development and general knowledge -were tested in a factor analysis of data on over 16,000 kindergarten children. The factor analyses upheld the first three domains, but revealed the need to develop two new ones, resulting in the final version of the EDI consisting of: physical health and well-being, social competence, emotional maturity, language and cognitive development, communication skills and general knowledge domains. These final domains showed good reliability levels, comparable with other instruments. A separate study (N = 82) demonstrated consistent agreements in parent-teacher, interrater reliabilities, concurrent validity, and convergent validity. These results establish the EDI as a psychometrically adequate indicator of child well-being at school entry.