Health and Quality of Life Outcomes

Background: Investigations of the structure of psychological well-being items are useful for advancing knowledge of what dimensions define psychological well-being in practice. Ryff has proposed a multidimensional model of psychological well-being and her questionnaire items are widely used but their latent structure and factorial validity remains contentious. Methods: We applied latent variable models for factor analysis of ordinal/categorical data to a 42item version of Ryff's psychological well-being scales administered to women aged 52 in a UK birth cohort study (n = 1,179). Construct (predictive) validity was examined against a measure of mental health recorded one year later. Results: Inter-factor correlations among four of the first-order psychological well-being constructs were sufficiently high (> 0.80) to warrant a parsimonious representation as a secondorder general well-being dimension. Method factors for questions reflecting positive and negative item content, orthogonal to the construct factors and assumed independent of each other, improved model fit by removing nuisance variance. Predictive validity correlations between psychological well-being and a multidimensional measure of psychological distress were dominated by the contribution of environmental mastery, in keeping with earlier findings from cross-sectional studies that have correlated well-being and severity of depression. Conclusion: Our preferred model included a single second-order factor, loaded by four of the six first-order factors, two method factors, and two more distinct first-order factors. Psychological well-being is negatively associated with dimensions of mental health. Further investigation of precision of measurement across the health continuum is required. Published: 04 October 2006 Health and Quality of Life Outcomes 2006, 4:76 doi:10.1186/1477-7525-4-76 Received: 26 July 2006 Accepted: 04 October 2006 This article is available from: http://www.hqlo. com/content/4/1/76 © 2006 Abbott et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Page 1 of 16 (page number not for citation purposes) Health and Quality of Life Outcomes 2006, 4:76 http://www.hqlo. com/content/4/1/76 Background Recent years have seen a widening interest in research on aspects of well-being [1-4]. Extensive research on subjective well-being (SWB) which focuses mainly on how people feel, e.g. positive affect, negative affect and life satisfaction (see review by Diener et al.) [5], has begun to be complemented by a heightened interest in how well people perceive aspects of their functioning, e.g. the extent to which they feel they are in control of their lives, feel that what they do is meaningful and worthwhile, and have good relationships with others e.g. [6,7]. This perspective is often referred to as psychological well-being (PWB) and is based on a eudaimonic perspective, rather than the hedonic perspective of subjective well-being research. This new focus has necessitated the theoretical development of new constructs as well as questionnaire items to measure psychological well-being in clinical and population samples. The work of Ryff and colleagues has been at the forefront of this endeavour. Ryff's scales of Psychological Well-being [8,9] were designed to measure six theoretically motivated constructs of psychological well-being: autonomy – independence and self-determination; environmental mastery – the ability to manage one’s life; personal growth – being open to new experiences; positive relations with others– having satisfying high quality relationships; purpose in life – believing that one’s life is meaningful; and self-acceptance – a positive attitude towards oneself and one’s past life. Despite the widespread interest in Ryff's theoretical framework, and application of the Ryff PWB items, the psychometric properties of the proposed sub-scales remain contentious. In particular there has been concern over issues of factorial validity and distinctiveness. Do the items intended to measure each theoretical domain, really do so? Do the items capture information from more than one domain? Are fewer dimensions actually revealed by empirical data collected to test the multidimensional theory? Previous psychometric studies of the Ryff PWB are summarised in Table 1. To date no independent investigation of the factorial validity of Ryff's well-being items has unequivocally supported the a priori six-factor structure. Authors of existing studies either challenge the value of so many theoretical constructs, whose scores correlate >0.8 or 0.9, or have not confirmed the fit of the proposed model [10-14] Many of these studies have reached similar conclusions despite the analysis of different short and long forms of the Ryff scales. As shown in Table 1, versions with different numbers of items have been applied in a variety of settings and samples. The original instrument included 120 items (20 per dimension) but shorter versions comprising 84 items (14 per dimension), 54 items (9 per dimension), 42 items (7 per dimension) and 18 items (3 per dimension) are now widely used. It is important to note that the overlap among items in the alternative versions of the Ryff scales is limited; for example, the 18-item version has only six items in common with the 42-item version, one item for each dimension. Ryff's own studies [7,9] have reported high correlations among scores for the constructs that were proposed as independent. It is possible that the measures may not, in practice, adequately operationalise the constructs proposed by her theory. For example, in Ryff's first study, which employed 120 items, the inter-correlations among factor scores for the six dimensions ranged from 0.32 to 0.76. Associations were particularly strong between personal growth and purpose in life; self-acceptance and purpose in life; and environmental mastery and selfacceptance [9]. Indeed, the magnitude of these inter-factor associations prompted Ryff and Keyes [7] to estimate a second-order factor model which invoked a general PWB factor to explain associations among the first-order constructs, so clearly they acknowledged the high interdependencies among the six factors. In a psychometric investigation of multi-samples, Springer & Hauser [14] factor analysed Ryff PWB items from three large North American studies; the Wisconsin Longitudinal Survey (42-items and 12-items); MIDUS – Midlife in the United States (18-items) and the National Survey of Families and Households (NSFH II) (18-items). Their results, based on internal construct validity arguments alone, seem to provide yet further evidence that the Ryff PWB items may either measure less than six distinct constructs, or that the theoretical constructs exist at two levels of definition. Psychometric studies of multi-item questionnaires often see a need to isolate components of response tendency that are due to methodological features e.g. design or wording of items [15,16]. Springer & Hauser [14] introduced a single latent variable (a method factor) to isolate the covariance among responses common to all negatively worded Ryff items. In their study, this component of their model was found to considerably improve model fit. In their response [17] to a commentary on their conclusions by Ryff and Singer [18] they reported a test of a 4factor model based on the four most highly correlated dimensions (environmental mastery, personal growth, purpose in life and self-acceptance) and compared this to a 4-factor model using the same items but where item allocation was based on positive and negative wording Page 2 of 16 (page number not for citation purposes) H ea lth a nd Q ua lit y of L ife O ut co m es 2 00 6, 4 :7 6 ht tp :// w w w . h ql o. co m /c on te nt /4 /1 /7 6