Relating individual differences in nicotine dependence severity to underpinning motivational and pharmacological processes among smokers from vulnerable populations

Abstract

We examined whether elucidating underpinning smoking motivation and related pharmacological processes enhances understanding of nicotine dependence among smokers from vulnerable populations. Data were obtained between Oct, 2016 and Sept, 2019 from 745 adult smokers with co-morbid psychiatric conditions or socioeconomic disadvantage at University of Vermont, Brown University, Johns Hopkins University. Smoking motivation was assessed using the Cigarette Purchase Task (CPT), a behavioral-economic task that models the relative reinforcing value of smoking under varying monetary constraint. Dependence severity was measured using the Heaviness of Smoking Index (HSI), Fagerström Test for Nicotine Dependence total scores (FTND), and FTND total scores minus items 1 and 4 (FTND2,3,5,6). We also assessed associations between dependence severity and smoking motivation with nicotine levels and metabolism rate. Principal Component Analysis was used to examine the latent structure of the conventional five CPT indices; bivariate and multivariable modeling was used to test associations. Factor analysis resulted in a two-factor solution, Amplitude (demand unconstrained by price) and Persistence (price sensitivity). CPT latent factors were associated with each dependence-severity measure (ps ≤ 0.0001), with associations stronger for Amplitude than Persistence across each, especially HSI which was exclusively associated with Amplitude. Amplitude and each dependence measure were associated with nicotine intake (ps ≤ 0.0002); Persistence was not (p = .19). Demand Amplitude more than Persistence appears key to understanding individual differences in dependence severity. Regarding potential application, the results suggest a need for interventions that more effectively target demand Amplitude to make greater headway in reducing smoking in vulnerable populations. Trial Registration:clinicaltrials.gov identifiers: NCT02232737, NCT02250664, NCT02250534.

Keywords: Cigarette purchase task; Cotinine; Fagerström test for nicotine dependence; Heaviness of smoking index; Nicotine dependence; Relative reinforcing value; Vulnerable populations.

Copyright © 2020 Elsevier Inc. All rights reserved.

Figures

Figure 1.

Shown is an overall Cigarette Purchase Task demand curve representing the number of cigarettes purchased as a function of increasing price. R2 represents the fit to the data of the Exponential Demand Equation (see text for details) and bars represent ± SEM.

Figure 2.

Shown are best-fit lines for associations between scores on the Cigarette Purchase Task latent factors Amplitude (solid lines) and Persistence (hashed lines) with Heaviness of Smoking (HSI) total scores, Fagerström Test of Nicotine Dependence (FTND) total scores, and Fagerström Test of Nicotine Dependence total scores minus items 1 and 4 (FTND2,3,5,6). R2 values represent total variance in factor scores accounted for by increasing dependence-severity scores.

Figure 3.

Shown are best-fit lines for associations between Heaviness of Smoking (HSI) total scores, Fagerström Test of Nicotine Dependence (FTND) total scores, and Fagerström Test of Nicotine Dependence total scores minus items 1 and 4 (FTND2,3,5,6) with combined cotinine (COT) and 3’-hydroxycotinine (3-HC) levels (COT+3-HC ng/ml). R2 values represent total variance in dependence-severity scores accounted for by increasing COT+3-HC ng/ml levels.

Figure 4.

Shown are best-fit lines for associations between scores on the Cigarette Purchase Task latent factors Amplitude (solid lines) and Persistence (hashed lines) with combined cotinine (COT) and 3’-hydroxycotinine (3-HC) levels (COT+3-HC ng/ml). R2 values represent total variance in factor scores accounted for by increasing COT+3-HC ng/ml levels.