Integrating person-centered and variable-centered analyses: growth mixture modeling with latent trajectory classes.

BACKGROUND: Many alcohol research questions require methods that take a person-centered approach because the interest is in finding heterogeneous groups of individuals, such as those who are susceptible to alcohol dependence and those who are not. A person-centered focus also is useful with longitudinal data to represent heterogeneity in developmental trajectories. In alcohol, drug, and mental health research the recognition of heterogeneity has led to theories of multiple developmental pathways. METHODS: This paper gives a brief overview of new methods that integrate variable- and person-centered analyses. Methods discussed include latent class analysis, latent transition analysis, latent class growth analysis, growth mixture modeling, and general growth mixture modeling. These methods are presented in a general latent variable modeling framework that expands traditional latent variable modeling by including not only continuous latent variables but also categorical latent variables. RESULTS: Four examples that use the National Longitudinal Survey of Youth (NLSY) data are presented to illustrate latent class analysis, latent class growth analysis, growth mixture modeling, and general growth mixture modeling. Latent class analysis of antisocial behavior found four classes. Four heavy drinking trajectory classes were found. The relationship between the latent classes and background variables and consequences was studied. CONCLUSIONS: Person-centered and variable-centered analyses typically have been seen as different activities that use different types of models and software. This paper gives a brief overview of new methods that integrate variable- and person-centered analyses. The general framework makes it possible to combine these models and to study new models serving as a stimulus for asking research questions that have both person- and variable-centered aspects.

The development of heavy drinking and alcohol-related problems from ages 18 to 37 in a U.S. national sample.

OBJECTIVE: The purpose of this study is to add to the understanding of the development of heavy alcohol use and alcohol-related problems by examining data from the National Longitudinal Survey of Youth (NLSY), a general population sample that contains information on alcohol use for the ages 18-37. A key question in this study is how background characteristics of the individual influence this development and whether the influence of these background characteristics changes over time. METHOD: The data used in this study are a general population sample (N = 7,859) from the National Longitudinal Survey of Youth (NLSY). This study uses a multivariate outcome approach that focuses on individual variation in trajectories over age. The statistical analysis uses random coefficients in a latent variable framework. Across-age changes in the importance of the influence of background variables on the outcomes are modeled using varying centering points. RESULTS: A key finding is that dropping out of high school has no effect on alcohol-related problems for individuals in their mid-twenties, but is associated with significantly increased levels of alcohol-related problems for individuals in their mid-thirties. In contrast, going on to college is associated with lower levels of heavy drinking when individuals reach their late twenties and their thirties. Strong gender and ethnicity effects seen in the twenties diminish when individuals reach their thirties. CONCLUSIONS: The trajectory analysis expands the knowledge of problematic alcohol development for individuals in their late twenties and thirties. The increasing detrimental effect of dropping out of high school up to the age 37 endpoint of the study raises questions about the effects in later life of dropping out of high school.

Effectiveness of the California 1990-1991 tobacco education media campaign.

The California Department of Health Services conducted a $28,600,000 tobacco education media campaign in 1990 and 1991. An independent evaluation of the media campaign featured four waves of data-gathering, one prior to the campaign's beginning and three at intervals thereafter. In all, 29,264 students in grades 4-12 and 6,785 adult smokers provided data for the evaluation. Through telephone interviews for adults and written questionnaires for students, these participants supplied information so that each person could be classified as exposed or unexposed to the media campaign's advertisements. Five criterion variables were used in the evaluation: campaign awareness, tobacco use, smokers' intention to quit, nonsmokers' intention to start, and attitudes toward smoking. Based chiefly on the differences between the results of waves 1 and 4, we believe the media campaign had a number of positive effects on California students. For adult smokers, the results were mixed.