Angela D. Bryan

A Baseline for the Multivariate Comparison of Resting-State Networks

As the size of functional and structural MRI datasets expands, it becomes increasingly important to establish a baseline from which diagnostic relevance may be determined, a processing strategy that efficiently prepares data for analysis, and a statistical approach that identifies important effects in a manner that is both robust and reproducible. In this paper, we introduce a multivariate analytic approach that optimizes sensitivity and reduces unnecessary testing. We demonstrate the utility of this mega-analytic approach by identifying the effects of age and gender on the resting-state networks (RSNs) of 603 healthy adolescents and adults (mean age: 23.4 years, range: 12–71 years). Data were collected on the same scanner, preprocessed using an automated analysis pipeline based in SPM, and studied using group independent component analysis. RSNs were identified and evaluated in terms of three primary outcome measures: time course spectral power, spatial map intensity, and functional network connectivity. Results revealed robust effects of age on all three outcome measures, largely indicating decreases in network coherence and connectivity with increasing age. Gender effects were of smaller magnitude but suggested stronger intra-network connectivity in females and more inter-network connectivity in males, particularly with regard to sensorimotor networks. These findings, along with the analysis approach and statistical framework described here, provide a useful baseline for future investigations of brain networks in health and disease.

Relationships Between Future Orientation, Impulsive Sensation Seeking, and Risk Behavior Among Adjudicated Adolescents.

Because of high levels of risk behavior, adjudicated adolescents are at high risk for negative health outcomes such as nicotine and drug addiction and sexually transmitted diseases. The goal of this article is to examine relationships between future orientation and impulsive-sensation-seeking personality constructs to risk behaviors among 300 adjudicated adolescents. Significant relationships between impulsive sensation seeking and future orientation were found for several risk behaviors. Individuals with more positive future orientation were less likely to use marijuana, hard drugs, alcohol during sex, had fewer alcohol problems, had lower levels of alcohol frequency and quantity of use, and perceived greater risks associated with such behaviors. Higher impulsivity reliably predicted alcohol problems, alcohol use, condom use, and cigarette smoking.

Clinician-delivered intervention during routine clinical care reduces unprotected sexual behavior among HIV-infected patients.

Objective:To evaluate the effectiveness of a clinician-delivered intervention, implemented during routine clinical care, in reducing unprotected sexual behavior of HIV-infected patients. Design:A prospective clinical trial comparing the impact of a clinician-delivered intervention arm vs. a standard-of-care control arm on unprotected sexual behavior of HIV-infected patients. Setting:The 2 largest HIV clinics in Connecticut. Participants:A total of 497 HIV-infected patients, aged ≥18 years, receiving HIV clinical care. Intervention:HIV clinical care providers conducted brief client-centered interventions at each clinical encounter that were designed to help HIV-infected patients reduce unprotected sexual behavior. Main Outcome Measures:Unprotected insertive and receptive vaginal and anal intercourse and unprotected insertive oral sex; unprotected insertive and receptive vaginal and anal intercourse only. Results:HIV-infected patients who received the clinician-delivered intervention showed significantly reduced unprotected insertive and receptive vaginal and anal intercourse and insertive oral sex over a follow-up interval of 18 months (P < 0.05). These behaviors increased across the study interval for patients in the standard-of-care control arm (P < 0.01). For the measure of unprotected insertive and receptive vaginal and anal sex only, there was a trend toward a reduction in unprotected sex among intervention arm participants over time (P < 0.09), and a significant increase in unprotected sex in the standard-of-care control arm (P < 0.01). Conclusions:A clinician-delivered HIV prevention intervention targeting HIV-infected patients resulted in reductions in unprotected sex. Interventions of this kind should be integrated into routine HIV clinical care.

Increasing condom use: Evaluation of a theory-based intervention to prevent sexually transmitted diseases in young women

A multicomponent intervention to increase condom use in sexually active young women was designed, implemented, and evaluated in a randomized experiment. Participants were 198 unmarried female college students (mean age = 18.6 years) who received a 1-session condom promotion intervention or a control (stress management) intervention. The condom promotion intervention led to increased self-reported condom use up to 6 months following intervention as well as positive changes in perceived benefits of condom use, affective attitudes toward condom use and condom users, perceived acceptance of sexuality, control over the sexual encounter, perceived self-efficacy for condom use, and intentions to use condoms. Mediational analysis illustrated the mechanisms of the condom promotion intervention effects, linking psychological constructs affected by the intervention (perceived benefits, acceptance of sexuality, control over the sexual encounter, attitudes toward condoms, and self-efficacy for condom use) to condom use intentions.

The DRD4 VNTR Polymorphism Moderates Craving After Alcohol Consumption

Recent research has suggested that alterations in mesolimbic dopamine neurotransmission are central to the development and expression of craving for alcohol. Because the D4 dopamine receptor gene, variable numbers of tandem repeats (DRD4 VNTR) polymorphism putatively expresses functional differences in dopamine receptors, the present study tested whether this polymorphism influences the effects of a priming dose of alcohol on craving. Participants consumed 3 alcoholic drinks or 3 control drinks and completed measures of craving after each drink. Participants who were homozygous or heterozygous for the 7 (or longer) repeat allele were classified as DRD4 L, whereas the other participants were classified as DRD4 S. Results suggested that DRD4 L participants demonstrated significantly higher craving after consumption of alcohol as compared with the control beverage.

Population Stratification in the Candidate Gene Study: Fatal Threat or Red Herring?

Advances in molecular genetics have provided behavioral scientists with a means of investigating the influence of genetic factors on human behavior. Unfortunately, recent candidate gene studies have produced inconsistent results, and a frequent scapegoat for the lack of replication across studies is the threat of population stratification. This review of the literature on population stratification suggests that the threat may be a red herring. Reliable findings will require improved specification and measurement of the behavioral phenotypes in question, a renewed focus on internal validity, and the specification and testing of genetic factors in the context of longitudinal multivariate models. In this respect, behavioral scientists are well suited to investigating genetic factors that influence psychological mechanisms.

The DRD4 VNTR polymorphism influences reactivity to smoking cues

Recent research has indicated that craving for tobacco can be reliably elicited by exposure to smoking cues, suggesting that cue-elicited craving for tobacco may be a useful phenotype for research on genetic factors related to nicotine dependence. Given the potential role of dopamine in cue-elicited craving, the authors examined whether the DRD4 VNTR polymorphism is associated with cue-elicited craving for tobacco. Participants who were homozygous or heterozygous for the 7 repeat (or longer) allele were classified as DRD4 L, and all other participants were classified as DRD4 S. Participants were exposed to smoking cues before smoking either high-nicotine cigarettes or control cigarettes. Analyses suggested that participants in the L group demonstrated significantly greater craving, more arousal, less positive affect, and more attention to the smoking cues than did the participants in the S group.

Young women's condom use: the influence of acceptance of sexuality, control over the sexual encounter, and perceived susceptibility to common STDs.

A comprehensive model of the determinants of condom use among young women was developed, tested, and replicated, with longitudinal follow-up to assess predictive utility of the model for condom use over time. Participants in Study 1 and Study 2 were 198 female undergraduates (mean age, 18.6 years) and 238 female undergraduates (mean age, 19.1 years), respectively. Acceptance of sexuality and control over the sexual encounter were related to a multidimensional measure of condom use self-efficacy, which predicted condom use intentions. Perceived susceptibility to STDs was both directly related to intentions and indirectly related through perceived benefits and attitudes about condom use. Intentions predicted subsequent reports of condom use. The model suggests foci for condom use interventions for young women.

Randomized Trial of Group Interventions to Reduce HIV/STD Risk and Change Theoretical Mediators among Detained Adolescents.

Criminally involved adolescents engage in high levels of risky sexual behavior and alcohol use, and alcohol use may contribute to lack of condom use. Detained adolescents (n = 484) were randomized to (1) a theory-based sexual risk reduction intervention (GPI), (2) the GPI condition with a group-based alcohol risk reduction motivational enhancement therapy component (GPI + GMET), or (3) an information-only control (INFO). All interventions were presented in same-sex groups in single sessions lasting from 2 to 4 hr. Changes to putative theoretical mediators (attitudes, perceived norms, self-efficacy, and intentions) were measured immediately following intervention administration. The primary outcomes were risky sexual behavior and sexual behavior while drinking measured 3 months later (65.1% retention). The GPI + GMET intervention demonstrated superiority over both other conditions in influencing theoretical mediators and over the INFO control in reducing risky sexual behavior. Self-efficacy and intentions were significant mediators between condition and later risky sexual behavior. This study contributes to an understanding of harm reduction among high-risk adolescents and has implications for understanding circumstances in which the inclusion of GMET components may be effective.

Mediational analysis in HIV/AIDS research: estimating multivariate path analytic models in a structural equation modeling framework.

Mediational analyses have been recognized as useful in answering two broad questions that arise in HIV/AIDS research, those of theoretical model testing and of the effectiveness of multicomponent interventions. This article serves as a primer for those wishing to use mediation techniques in their own research, with a specific focus on mediation applied in the context of path analysis within a structural equation modeling (SEM) framework. Mediational analyses and the SEM framework are reviewed at a general level, followed by a discussion of the techniques as applied to complex research designs, such as models with multiple mediators, multilevel or longitudinal data, categorical outcomes, and problematic data (e.g., missing data, nonnormally distributed variables). Issues of statistical power and of testing the significance of the mediated effect are also discussed. Concrete examples that include computer syntax and output are provided to demonstrate the application of these techniques to testing a theoretical model and to the evaluation of a multicomponent intervention.