Biomedical subjects

Angela Bryan

Publications and source records attributed to Angela Bryan.

14 recordsLinked to original sources

PubMed2007

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.

Data Interpretation, Statistical↗

PubMed2007

A transdisciplinary model integrating genetic, physiological, and psychological correlates of voluntary exercise.

OBJECTIVE: Physical inactivity contributes to as many as 250,000 premature deaths per year (R. R. Pate et al., 1995). The authors' objective was to test a transdisciplinary model of the ways in which genetic variants, physiological factors, and psychological factors are thought to influence exercise with 64 healthy, regular exercisers. DESIGN: In a within-subjects design, psychological and physiological responses to exercise were compared with responses to a sedentary activity. MAIN OUTCOME MEASURES: The authors measured affective state, perceived exertion, heart rate, and temperature change in response to moderate exercise versus sedentary activity. They also quantified genotypes on a single nucleotide polymorphism in the brain-derived neurotrophic factor (BDNF) gene. RESULTS AND CONCLUSIONS: The data show a relation between increases in positive affective states and acute exercise behavior, as opposed to a sedentary control. The BDNF gene moderated the effect of exercise on mood, heart rate, and perceived exertion. Physiological factors were, in turn, related to mood response, and mood response was a significant correlate of motivation to exercise in the future and of current exercise behavior. The model has potential as a framework for the basic study of the genetic, physiological, and psychological processes involved with voluntary exercise and as a tool for the applied examination of tailored exercise interventions and their efficacy for different subsets of individuals.

Adolescent↗

PubMed2006

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 > or =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.

Adult↗

PubMed2006

Condom use among South African adolescents: developing and testing theoretical models of intentions and behavior.

We developed and tested models of intentions and behavior among adolescents from Cape Town, South Africa. Data from 261 participants who completed an initial measure of attitudes, beliefs, and prior behavior were used to develop a model of intentions to use condoms based on the Theory of Planned Behavior (TPB) and additional constructs found to be important in previous research with adolescents. Of the initial sample, 227 (87%) completed a behavioral follow-up 4 months later, and approximately one-third of those (n=72; 44 boys and 30 girls) reported having had sex in the prior 4 months. Data from this smaller sample were used to develop a model of condom use behavior based on intentions (as per the TPB) and the additional sub-population relevant constructs. Analyses generally supported the validity of the TPB in this context for predicting intentions and behavior. HIV knowledge and positive outlook (self-esteem and future optimism) were significantly related to TPB predictors of intentions. Intentions, acceptance of sexuality, and gender were significant predictors of behavior. Implications for the status of the TPB and the design of interventions for South African adolescents are discussed.

Adolescent↗

PubMed2006

Effectiveness of an HIV prevention intervention in prison among African Americans, Hispanics, and Caucasians.

Prisons and prison inmates present important targets for HIV/AIDS prevention interventions. Inmates often have histories of high-risk behavior that place them in danger of contracting HIV/AIDS, and rates of HIV/AIDS tend to be much higher in this population. The goal of this study was to assess the effectiveness of a prison-based HIV/AIDS intervention to change attitudes toward HIV prevention, norms supporting HIV prevention, perceived behavioral control (i.e., self-efficacy) for HIV prevention behaviors, and intentions to engage in HIV prevention behaviors postrelease. The intervention also had the goal of encouraging inmates to become HIV/AIDS peer educators. The intervention appeared most successful at influencing beliefs and behaviors related to peer education and somewhat successful at influencing beliefs and intentions related to condom use. Analyses also showed some significant differences in effectiveness by race/ethnicity. Results are discussed from the perspectives of both research and practice with regard to prison-based HIV prevention efforts.

Adolescent↗

PubMed2005

Sex differences in affective responses to homoerotic stimuli: evidence for an unconscious bias among heterosexual men, but not heterosexual women.

Antigay bias is a well-documented social problem among heterosexual men, though heterosexual women display a lesser tendency toward this bias. Startle eye blink has been established as a valid measure of the affective component of antigay bias in heterosexual men. In the current study, a sample of 91 heterosexual women and 87 heterosexual men were exposed to a variety of sexual photographic stimuli accompanied by startle probes. Heterosexual men who expressed more bias against gay men using a social distance measure (i.e., discomfort with being in close quarters with a gay man) displayed a startle response consistent with greater negative affect (e.g., fear and disgust) toward gay male stimuli, while those with less self-reported antigay bias did not display a physiological bias against gay men, and none of these men showed a relationship between bias against lesbians and physiological responses while viewing lesbian images. There were no such physiological manifestations of antigay bias in heterosexual women while viewing lesbian or gay male images, even among those who self-reported such bias. It appears that heterosexual women do not tend to have the same affective response toward homosexuals that some heterosexual men experience.

Adult↗

PubMed2005

Condom use among high-risk adolescents: testing the influence of alcohol use on the relationship of cognitive correlates of behavior.

The goal of this study was the exploration of distal effects of alcohol use on condom use. Criminally involved adolescents completed an initial measure of attitudes, beliefs, and prior behavior. Of the 300 who completed the initial measurement, 267 (89%) completed a behavioral assessment 6 months later. Analyses validated a theoretical model of condom use intentions and indicated that intentions and attitudes measured at baseline were significant predictors of condom use behavior 6 months later. Neither alcohol use nor alcohol problems moderated relationships among model variables or the influence of intentions and attitudes on behavior. The findings do not support a distal role for alcohol use in altering the cognitive correlates of condom use intentions and behavior among high-risk adolescents.

Adolescent↗

PubMed2004

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.

Journal Article↗

PubMed2004

Tobacco and alcohol use as an explanation for the association between externalizing behavior and illicit drug use among delinquent adolescents.

The prevalence and persistence of adolescent substance use and abuse is a national health issue, and substance use among adolescents is frequently comorbid with other psychiatric disorders. Most studies in this area utilize samples of middle or high school students or from inpatient settings. Less is known about substance use and psychiatric comorbidity among delinquent adolescents. The present study examined data from two cohorts of juvenile offenders collected over a 2-year period (n = 245, n = 299). Participants reported frequency of cigarette, alcohol, marijuana, and other substance use. Participants' parents completed a measure of behavior problems. Path analyses suggested that parental reports of externalizing problems were significantly related to self-reported substance use while parental reports of internalizing problems were not. Results also suggested that smoking and alcohol use act as mediators between externalizing problems and marijuana and other drug use. Although there were some mean differences by gender, the pattern of relationships amongst the variables did not differ by gender. Implications of the findings and future directions are discussed.

Adolescent↗

PubMed2004

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.

Case-Control Studies↗

PubMed2002

It ain't necessarily so: most women do not strongly prefer female obstetrician-gynaecologists.

OBJECTIVE: To examine whether Canadian women seeking care from obstetrician-gynaecologists prefer to see female or male physicians or have no strong preference in this regard. METHODS: A self-administered questionnaire assessing women's "strong preference" for female or male obstetrician-gynaecologists, or their lack of a strong preference in this area, was completed by 409 women (93.8% response rate) attending two hospital-based obstetrics and gynaecology outpatient clinics in London, Ontario. RESULTS: Overall, 75% of women stated that they had no strong preference concerning the gender of their obstetrician-gynaecologist; 21% strongly preferred a female obstetrician-gynaecologist; and 4% strongly preferred a male obstetrician-gynaecologist. Women who were single, pregnant, or had a history of abortion, sexual coercion, relationship violence, sexual dysfunction, or sexually transmitted disease were no more likely to prefer to see a female obstetrician-gynaecologist than were women without these characteristics. CONCLUSION: A clear majority of women expressed no strong preference for the gender of their obstetrician-gynaecologist, and preference for a female obstetrician-gynaecologist was not associated with a history of sensitive gender-related medical concerns. Nationally representative research is needed to clarify women's preferences in this domain across the regions of Canada and to determine the strength and correlates of any such preferences. Patient care and human rights implications of women's preference for the gender of their obstetrician-gynaecologist will need to be carefully considered as well.

Female↗

PubMed2002

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.

Adult↗

PubMed2002

Tests of the mediational role of preparatory safer sexual behavior in the context of the theory of planned behavior.

The present research details 2 empirical tests within the context of the theory of planned behavior (I. Ajzen & T. Madden, 1986) of the assumption that preparatory behaviors (e.g., discussing safer sex, obtaining condoms) play a mediational role in the relation between psychological variables (e.g., attitudes toward safer sex, social norms about safer sex) and condom use. The assumption of the mediational role of preparatory behaviors is examined in sexually experienced samples from 2 different populations: inner-city high school students (N = 226) and college students (N = 160). The results suggest that the mediational role of preparatory behaviors is a highly significant one. Results indicate no gender differences with regard to the main mediational hypotheses. The methodological, theoretical, and practical implications and importance of these findings are discussed.

Adolescent↗

PubMed2002

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.

Adult↗