Reliability of Selected Measures of Nicotine Dependence among Adolescents

Abstract

PURPOSE: To examine the test retest reliability, internal consistency, and convergent construct validity of selected measures of nicotine dependence (ND) among adolescents.

METHODS: Self-reports of sociodemographic characteristics and smoking behavior were collected in a convenience sample of 238 high school students aged 13 to 19 years. ND was measured in the Hooked on Nicotine Checklist (HONC), the Stanford Dependence Index (SDI) and in 45 new items identified in consultation with experts and focus group interviews with adolescent smokers.

RESULTS: Test retest reliability among past 3-month smokers indicated good to excellent reliability coefficients for HONC items (κ 0.61 to 0.93), except one item that tapped feelings of depression on withdrawal (κ = 0.34). Intraclass correlation coefficients for SDI items ranged from 0.71 to 0.77. Test retest reliability coefficients for the 45 new items ranged from 0.20 to 0.90. The HONC and SDI demonstrated good internal consistency (Cronbach's α = 0.90 and 0.78, respectively). Convergent construct validity against cigarette exposure was demonstrated for the HONC, SDI, and most of the 45 new items.

CONCLUSIONS: The HONC and SDI demonstrated excellent and good psychometric properties, respectively. Most of the 45 new items hold promise as indicators of ND in youth, and should be further investigated.

Introduction

Although classic models postulate that nicotine dependence (ND) develops only after several years of regular smoking (1), several lines of recent evidence suggest that symptoms of ND exist even in the early stages of smoking onset. First, young smokers absorb as much nicotine per cigarette as do adults, even with their first few cigarettes 2, 3. Second, surveys have documented ND symptoms including cravings and withdrawal symptoms among adolescent smokers 4, 5, 6, 7, 8, 9. Third, although substantial proportions of youth smokers try to quit, the success rate is low 10, 11; adolescents who attempt to quit report withdrawal symptoms 12, 13 and the number of symptoms and likelihood of relapse is related to the number of cigarettes smoked 12, 14. Finally, a recent study provided the first prospective evidence that ND symptoms occur early in the smoking onset process, before daily use, with low exposure to cigarettes, and over very short time intervals after smoking initiation (15). Collectively these findings suggest that we need to learn more about how early in the smoking onset process ND symptoms develop, and when these symptoms begin to influence patterns of smoking.

However, a major barrier to studying the natural history of ND is the lack of a widely accepted, theoretically derived, and psychometrically sound tool to measure ND in adolescents (16). More specifically, a valid and reliable instrument is needed to assess ND symptoms early in the onset process when smoking can be sporadic, irregular, and infrequent. While several instruments have been used to measure ND in both adults and adolescents, each has been criticized. The DSM definition of ND provides criteria to assess ND (17), but was not derived from addiction theory and is not accepted as a “gold standard” 16, 18, 19. Individual researchers must translate these criteria into survey items, so those instruments based on DSM criteria are not standardized across studies (18). In addition, although DSM criteria have been applied in modified forms to adolescents 9, 18, 20, 21, 22 they were not developed, tested, or validated for use in adolescents.

The Fagerstrom Tolerance Questionnaire (FTQ) (23) assesses the compulsion to use cigarettes to achieve pleasurable effects and to avoid withdrawal symptoms, and is widely used in research to categorize adult smokers by degree of ND. It was adapted for use among youth by Prokhorov et al. 24, 25 and in the Stanford Dependence Index (SDI) (13). While the FTQ (and SDI) measures the strength of physical dependence, it was not designed to measure when ND begins and therefore might not be useful in studies in which detection of early ND symptoms are crucial 16, 23, 24, 26. Although cotinine is used to describe dependence, it in fact measures nicotine intake rather than ND 9, 16, 27. Finally, the ICD-10 includes criteria for assessing tobacco dependence, but has not been used in studies of adolescents (28).

While measures of ND for adolescent smokers exist, their psychometric properties including test retest reliability, internal consistency (i.e. the extent to which individual items in a multi-item indicator, scale or index all measure the same underlying concept), and their content, convergent construct and criterion-related validity have not yet been systematically compared. This study describes selected psychometric properties of two measures of ND for adolescents — the SDI, and a newer measure, the Hooked on Nicotine Checklist (HONC), which was used in a recent study on the natural history of ND in adolescents (15). We also tested 45 “new” items that emerged from telephone consultation with seven North American experts on youth smoking, and from six focus group interviews with teenage smokers aged 14 to 17 years (29).