1. Dynamic changes in stress and drug use in pregnant women using latent change scores Complex patterns of dynamic changes in stress and drug use in pregnant women. A layman’s visual modeling introduction to latent change score analysis 1 Ethel Donaghue TRIPP Center, UConn Health Center; 2 CIRA Center for Interdisciplinary Research on AIDS at Yale U.; 3 Department of Psychiatry, University of Connecticut School of Medicine; 4 Eastern Conn State University Emil Coman PhD 1,2, Helen Wu PhD 3, Maria A Coman MS 4 Abstract We introduce Latent Change Score (LCS) modeling using visual models and illustrate the method with a dataset from a study of pregnant women. We tested bivariate LCS models with stress and drug use, measured over eight time points. We tested LCS models with same- and other-variable prior values as predictors of changes. LCS models show that pregnancy changes the dynamical coupling links between perceived stress and drug use. We present limitations of complex LCS models and offer practical solutions to overcome LCS modeling challenges. Key RESEARCH QUESTIONS: 1. Are drug use and stress dynamically linked in young drug-using women? Then: which is leading the other one? 2. How does this dynamic coupling relation change due to pregnancy? References 1. McArdle, J., J. (1991). Structural models of developmental theory in psychology. In P. V. Geert & L. Mos (Eds.), Annals of theoretical psychology (Vol. II, pp. 139-160). New York: Plenum Publishers. 2. McArdle, J. J. (1991). Comments on “latent variable models for studying difference and changes” In L. Collins & J. L. Horn (Eds.), Best Methods for the Analysis of Change (pp. 164-169). Washington, D.C.: APA Press. 3. McArdle, J. J. (2009). Latent Variable Modeling of Differences and Changes with Longitudinal Data. Annual Review of Psychology, 60, 577-605. 4. Coman, E. N., Picho, K., McArdle, J. J., Villagra, V., Dierker, L., & Iordache, E. (2013). The paired t-test as a simple latent change score model. Frontiers in Quantitative Psychology and Measurement, 4, Article 738. doi: 10.3389/fpsyg.2013.00738 5. Coman, E., Iordache, E., & Coman, M. A. (2013). Testing mediation the way it was meant to be: changes leading to changes then to other changes. Dynamic mediation implemented with latent change scores. Paper presented at the Modern Modeling Methods (M3) Conference, May 21-22, Storrs, CT. 6. Grimm, K. J., An, Y., McArdle, J. J., Zonderman, A. B., & Resnick, S. M. (2012). Recent Changes Leading to Subsequent Changes: Extensions of Multivariate Latent Difference Score Models. Structural Equation Modeling: A Multidisciplinary Journal, 19(2), 268-292. Acknowlegements The first author thanks his causal modeling mentor David Kenny, and his long-time community-based research mentor Marlene Berg. Summary description of perceived stress Latent Change Score (LCS) introduction Statistical models are meant to explain and predict : 1. differences (between individual cases and groups); 2. changes (over time); 3. differences in changes; 4. changes in differences; 5. dynamic processes. Changes can be shown visually in a ‘pair-link diagram’: When 2 outcomes change side-by-side, their changes can become the focus of analysis: LCS logic and benefits LCS allows for EXPLANATION and PREDICTION of changes due to: 1.Prior values of same-variable (self-feedback/self-mediation [5]) 2.Prior values of other-variable (coupling) 3.Prior changes in other variables (changes-to-changes [6]) LCS is the simplest and most creative statistical trick devised by Jack McArdle [1-3] to capture and model changes: LCS models directly insert the change score in a structural model, however, as a latent variable. Rewriting the ΔY 21 = Y 2 − Y 1 change equation as LCS 21 = Y 2 − Y 1, one can define the true changes with the multiple regression: Y 2 =0 + 1 ∗ Y 1 + 1 ∗ LCS 21 + 0 [4] If one builds LCS scores for each pair of the outcomes of interest, one can build models that can look like (in AMOS see tripp.uchc.edu/modeling for downloads). This 2-group LCS coupling model fit well: χ 2 (55) = 72.4, p =.057, considering this is a 2-group LCS model (see [6] e.g., where only log- likelihoods are sometimes reported). A better fitting variant yielded a negative residual variance, which was then set to +.001. Red/Green estimates are for Pregnant/Non-pregnant drug using women. The model indicates that: 1. Drug changes around delivery become dependent on prior drug use in Pregnant women (P). 2. Stress changes around delivery become dependent on prior stress in P. 3. The initial NS coupling link between prior drug use to stress changes (around conception) in Non-Pregnant women (N-P) becomes significant in P. 4. The subsequent similar significant link in N-P becomes NS in P, during pregnancy (2 to 8 months). 5. The significant coupling link between prior stress and drug use changes (2 to 8 months) in N-P becomes NS in P women. 6. Similarly, the near-significant coupling link (p =.062) between prior stress and drug use changes around ‘delivery ‘ in N-P becomes NS in P women. Conclusions: 1. There are several dynamic links between stress and drug use in women, and 2. Pregnancy changes these dynamic links. Latent Change Score modeling challenges 1.LCS models are hard to fit : there is little published literature on well fitting (=NS χ 2 test) models. 2.LCS models are often very fussy: they can yield: 1. negative variances (not acceptable); 2. wild values for standard errors (= indicates problems!); 3. wild estimated parameters (needs inspection). 3.Alternative LCS models for the same 2 outcomes can become a hassle: building upon simple models those with increasingly more links in 1 (& >1 group) is an art. 4.However, there are beaten paths one can follow to sucessfuly replicate such analyses: public models/syntaxes. Study description Sample: 49 drug using women attending community-based family planning clinics who became pregnant during the course of a longitudinal study of women’s drug use. These participants were compared to 65 matched drug using non-pregnant women who did not become pregnant during the study. Woman who screened positive for substance use in the last 12 months either by urine testing or self-report, participated in the longitudinal study (n=114). Face-to- face interviews were conducted at baseline (-1 month), and seven at follow-ups; here we report on analyses around conception(1 month prior and the 2 nd month of pregnancy) and around delivery (8 th and 10 th month of pregnancy). Key Measures: Perceived stress scale (PSS): This 10-item scale measures the degree to which life situations are appraised as stressful, with items designed to determine how unpredictable, uncontrollable, and overloaded respondents have found their lives in the last 30 days. Drug use at each time point was based on self-reported weekly drug use for the past two months at each interview. The total number of different drugs used in two months was a summation of all types of drugs including marijuana, cocaine, PCP, LSD, inhalant, and other reported during that 2 months of interviews. New England Psychological Association & Northeast Conference For Teachers of Psychology, Oct. 18-19, 2013 Summary description of drug use