1
|
Jemmott LS, Jemmott JB, Stevenson HS, Chittamuru D. Barber-Led HIV/Sexually Transmitted Infection Risk Reduction for Young African-American Men: Efficacy and Mediation in a Cluster Randomized Controlled Trial. J Adolesc Health 2023; 72:575-582. [PMID: 36690549 DOI: 10.1016/j.jadohealth.2022.10.030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2021] [Revised: 10/17/2022] [Accepted: 10/19/2022] [Indexed: 01/22/2023]
Abstract
PURPOSE The aim of this study is to evaluate the efficacy and mediation of a culturally appropriate, theory-based HIV/STI (sexually transmitted infection) risk-reduction intervention delivered in barbershops by barbers via iPads to African-American young men in reducing sexual risk behaviors. METHODS In a cluster randomized controlled trial, 24 matched pairs of barbershops serving African-American men ages 18-24 in the 10 Philadelphia, PA zip codes with the highest HIV/AIDS prevalence were randomized to implement via iPads one of 2 interventions: "Shape Up! Barbers Building Better Brothers," an HIV/STI risk-reduction intervention based on the theory of planned behavior and formative research or an attention-matched violence-prevention control intervention. The primary outcome was self-reported consistent condom use 3, 6, and 12 months postintervention, controlling for baseline consistent condom use. RESULTS Participants were 618 men, 319 in the HIV/STI intervention and 299 in the control intervention. Generalized estimating equation analysis indicated that the direct effect of the HIV/STI intervention in increasing consistent condom use postintervention was nonsignificant (odds ratio = 1.13, 95% confidence interval: 0.73-1.75), adjusting for clustering among participants in barbershops and baseline condom use. However, mediation analysis using the product-of-coefficients approach revealed indirect effects of the intervention. Consistent with the theory of planned behavior, the intervention increased behavioral beliefs and self-efficacy regarding using condoms, which raised condom use intention, which, in turn, boosted consistent condom use. DISCUSSION Sexual risks among young African-American men can be reduced by barber-led theory-based, culturally appropriate HIV/STI risk-reduction interventions in barbershops in high HIV prevalence neighborhoods that increase behavioral beliefs and self-efficacy.
Collapse
Affiliation(s)
- Loretta S Jemmott
- University of Pennsylvania School of Nursing, Philadelphia, Pennsylvania.
| | - John B Jemmott
- University of Pennsylvania Annenberg School for Communication, Philadelphia, Pennsylvania; Department of Psychiatry, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
| | - Howard S Stevenson
- University of Pennsylvania Graduate School of Education, Philadelphia, Pennsylvania
| | - Deepti Chittamuru
- University of Pennsylvania Annenberg School for Communication, Philadelphia, Pennsylvania; School of Social Sciences, Arts, and Humanities, University of California, Merced, California
| |
Collapse
|
2
|
Pitpitan EV, MacKinnon DP, Eaton LA, Smith LR, Wagman J, Patterson TL. Using Novel Approaches to Evaluate Behavioral Interventions: Overlooked Significant HIV Prevention Effects in the HPTN 015 Project EXPLORE. J Acquir Immune Defic Syndr 2021; 87:1128-1135. [PMID: 33901103 PMCID: PMC8496973 DOI: 10.1097/qai.0000000000002711] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Accepted: 04/12/2021] [Indexed: 11/26/2022]
Abstract
BACKGROUND Mediated and moderated processes that lead to intervention efficacy may underlie results of trials ruled as nonefficacious. The overall purpose of this study was to examine such processes to explain the findings of one of the largest, rigorously conducted behavioral intervention randomized controlled trials, EXPLORE. METHODS Four thousand two hundred ninety-five HIV-negative men who have sex with men (MSM) in the United States were randomized in a 2-armed trial. Participants completed follow-up and an HIV test every 6 months up to 48 months. We used multiple and causal mediation analyses to test 5 mediators, including safer sex self-efficacy and condomless receptive anal sex with HIV-positive or status-unknown partners on our primary outcome (HIV seroconversion). We also examined whether intervention effects on the mediators would be moderated by robust correlates of HIV among MSM, including stimulant use. RESULTS There were significant effects of the intervention on all hypothesized mediators. Stimulant use moderated the effect on condomless receptive anal sex In stratified multiple mediation models, we found that among MSM with low stimulant use, the intervention significantly prevented HIV by reducing condomless receptive anal sex with HIV-positive or status-unknown partners. Among MSM with higher stimulant use, there were no indirect effects of the intervention on HIV through any of the hypothesized mediators. CONCLUSION The results suggest that the null effect found in the original EXPLORE trial might have occurred as a function of previously unexplored mediated and moderated processes. This study illustrates the value of testing mediated and moderated pathways in randomized trials, even in trials ruled out as nonefficacious.
Collapse
|
3
|
Berman M, Eaton LA, Watson RJ, Andrepont JL, Kalichman S. Social Distancing to Mitigate COVID-19 Risks Is Associated With COVID-19 Discriminatory Attitudes Among People Living with HIV. Ann Behav Med 2020; 54:728-737. [PMID: 32940326 PMCID: PMC7516104 DOI: 10.1093/abm/kaaa074] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Severe acute respiratory syndrome coronavirus-2, the virus that causes COVID-19, is an emerging pandemic with heightened concerns for people with compromised immune systems, including people living with HIV. PURPOSE In the absence of a vaccine, public health messaging to mitigate risks for COVID-19 primarily focuses on social distancing. Because people living with HIV commonly experience mistreatment associated with HIV, their response to social distancing may be complicated by psychosocial attitudes associated with COVID-19. METHODS To evaluate these relationships, we conducted a rapid-response, cross-sectional survey with people living with HIV (N = 149) to assess social distancing practices, COVID-19 discriminatory attitudes, COVID-19 xenophobic attitudes, HIV microaggressions, and concern over contracting COVID-19. Data were collected from participants enrolled in a larger ongoing study between March 30, 2020 and April 17, 2020. RESULTS Results indicated that choosing to socially distance to reduce COVID-19 exposure was associated with COVID-19 discriminatory attitudes, concerns of contracting COVID-19, and identifying as transgender. Likewise, social distancing imposed by others (e.g., cancelations and restrictions) was associated with concerns of contracting COVID-19. CONCLUSIONS Findings demonstrate that social distancing measures are related to concerns of contracting the virus and discriminatory attitudes toward those who are presumed to be living with COVID-19. These potentially negative psychosocial attitudes toward people perceived to have COVID-19 echo the discriminatory actions and attitudes that we continue to observe in HIV social sciences research.
Collapse
Affiliation(s)
- Marcie Berman
- Institute for Collaboration on Health, Intervention, and Policy, University of Connecticut, Storrs, CT, USA
| | - Lisa A Eaton
- Institute for Collaboration on Health, Intervention, and Policy, University of Connecticut, Storrs, CT, USA
| | - Ryan J Watson
- Institute for Collaboration on Health, Intervention, and Policy, University of Connecticut, Storrs, CT, USA
| | - J L Andrepont
- School of Public Policy, Oregon State University, Corvallis, OR, USA
| | - Seth Kalichman
- Institute for Collaboration on Health, Intervention, and Policy, University of Connecticut, Storrs, CT, USA
| |
Collapse
|
4
|
Eaton LA, Kalichman SC. Social and behavioral health responses to COVID-19: lessons learned from four decades of an HIV pandemic. J Behav Med 2020; 43:341-345. [PMID: 32333185 PMCID: PMC7182505 DOI: 10.1007/s10865-020-00157-y] [Citation(s) in RCA: 74] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 04/16/2020] [Indexed: 01/07/2023]
Abstract
Our public health approaches to addressing COVID-19 are heavily dependent on social and behavioral change strategies to halt transmissions. To date, biomedical forms of curative and preventative treatments for COVID-19 are at best limited. Four decades into the HIV epidemic we have learned a considerable amount of information regarding social and behavioral approaches to addressing disease transmission. Here we outline broad, scoping lessons learned from the HIV literature tailored to the nature of what we currently know about COVID-19. We focus on multiple levels of intervention including intrapersonal, interpersonal, community, and social factors, each of which provide a reference point for understanding and elaborating on social/behavioral lessons learned from HIV prevention and treatment research. The investments in HIV prevention and treatment research far outweigh any infectious disease in the history of public health, that is, until now with the emergence of COVID-19.
Collapse
Affiliation(s)
- Lisa A Eaton
- Human Development and Family Sciences, University of Connecticut, Storrs, CT, USA.
| | - Seth C Kalichman
- Psychological Sciences, University of Connecticut, Storrs, CT, USA
| |
Collapse
|
5
|
Flowers P, Wu O, Lorimer K, Ahmed B, Hesselgreaves H, MacDonald J, Cayless S, Hutchinson S, Elliott L, Sullivan A, Clutterbuck D, Rayment M, McDaid L. The clinical effectiveness of individual behaviour change interventions to reduce risky sexual behaviour after a negative human immunodeficiency virus test in men who have sex with men: systematic and realist reviews and intervention development. Health Technol Assess 2018; 21:1-164. [PMID: 28145220 DOI: 10.3310/hta21050] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Men who have sex with men (MSM) experience significant inequalities in health and well-being. They are the group in the UK at the highest risk of acquiring a human immunodeficiency virus (HIV) infection. Guidance relating to both HIV infection prevention, in general, and individual-level behaviour change interventions, in particular, is very limited. OBJECTIVES To conduct an evidence synthesis of the clinical effectiveness of behaviour change interventions to reduce risky sexual behaviour among MSM after a negative HIV infection test. To identify effective components within interventions in reducing HIV risk-related behaviours and develop a candidate intervention. To host expert events addressing the implementation and optimisation of a candidate intervention. DATA SOURCES All major electronic databases (British Education Index, BioMed Central, Cumulative Index to Nursing and Allied Health Literature, EMBASE, Educational Resource Index and Abstracts, Health and Medical Complete, MEDLINE, PsycARTICLES, PsycINFO, PubMed and Social Science Citation Index) were searched between January 2000 and December 2014. REVIEW METHODS A systematic review of the clinical effectiveness of individual behaviour change interventions was conducted. Interventions were examined using the behaviour change technique (BCT) taxonomy, theory coding assessment, mode of delivery and proximity to HIV infection testing. Data were summarised in narrative review and, when appropriate, meta-analysis was carried out. Supplemental analyses for the development of the candidate intervention focused on post hoc realist review method, the assessment of the sequential delivery and content of intervention components, and the social and historical context of primary studies. Expert panels reviewed the candidate intervention for issues of implementation and optimisation. RESULTS Overall, trials included in this review (n = 10) demonstrated that individual-level behaviour change interventions are effective in reducing key HIV infection risk-related behaviours. However, there was considerable clinical and methodological heterogeneity among the trials. Exploratory meta-analysis showed a statistically significant reduction in behaviours associated with high risk of HIV transmission (risk ratio 0.75, 95% confidence interval 0.62 to 0.91). Additional stratified analyses suggested that effectiveness may be enhanced through face-to-face contact immediately after testing, and that theory-based content and BCTs drawn from 'goals and planning' and 'identity' groups are important. All evidence collated in the review was synthesised to develop a candidate intervention. Experts highlighted overall acceptability of the intervention and outlined key ways that the candidate intervention could be optimised to enhance UK implementation. LIMITATIONS There was a limited number of primary studies. All were from outside the UK and were subject to considerable clinical, methodological and statistical heterogeneity. The findings of the meta-analysis must therefore be treated with caution. The lack of detailed intervention manuals limited the assessment of intervention content, delivery and fidelity. CONCLUSIONS Evidence regarding the effectiveness of behaviour change interventions suggests that they are effective in changing behaviour associated with HIV transmission. Exploratory stratified meta-analyses suggested that interventions should be delivered face to face and immediately after testing. There are uncertainties around the generalisability of these findings to the UK setting. However, UK experts found the intervention acceptable and provided ways of optimising the candidate intervention. FUTURE WORK There is a need for well-designed, UK-based trials of individual behaviour change interventions that clearly articulate intervention content and demonstrate intervention fidelity. STUDY REGISTRATION The study is registered as PROSPERO CRD42014009500. FUNDING The National Institute for Health Research Health Technology Assessment programme.
Collapse
Affiliation(s)
- Paul Flowers
- Department of Psychology, Social Work and Allied Health Sciences, Glasgow Caledonian University, Glasgow, UK
| | - Olivia Wu
- Health Economics and Health Technology Assessment and National Institute for Health Research Complex Reviews Support Unit, University of Glasgow, Glasgow, UK
| | - Karen Lorimer
- Department of Nursing and Community Health, Glasgow Caledonian University, Glasgow, UK
| | - Bipasha Ahmed
- GCU London, Glasgow Caledonian University, London, UK
| | - Hannah Hesselgreaves
- Health Economics and Health Technology Assessment and National Institute for Health Research Complex Reviews Support Unit, University of Glasgow, Glasgow, UK
| | - Jennifer MacDonald
- Department of Nursing and Community Health, Glasgow Caledonian University, Glasgow, UK
| | - Sandi Cayless
- Department of Psychology, Social Work and Allied Health Sciences, Glasgow Caledonian University, Glasgow, UK
| | - Sharon Hutchinson
- Department of Psychology, Social Work and Allied Health Sciences, Glasgow Caledonian University, Glasgow, UK
| | - Lawrie Elliott
- Department of Nursing and Community Health, Glasgow Caledonian University, Glasgow, UK
| | - Ann Sullivan
- Chelsea and Westminster Hospital NHS Foundation Trust, London, UK
| | | | - Michael Rayment
- Chelsea and Westminster Hospital NHS Foundation Trust, London, UK
| | - Lisa McDaid
- Chief Scientist Office/Medical Research Council Social and Public Health Sciences Unit, University of Glasgow, Glasgow, UK
| |
Collapse
|
6
|
Abstract
There is a strong push to conduct large-scale randomized controlled study designs in HIV prevention studies. In these randomized controlled studies, the primary research objective is typically to determine the treatment effect based on some biological outcome (eg, HIV infection). But many unused self-reported outcomes are also being collected. We illustrate the extent of this problem using the EXPLORE data as an example.
Collapse
|
7
|
Williams EC, Hahn JA, Saitz R, Bryant K, Lira MC, Samet JH. Alcohol Use and Human Immunodeficiency Virus (HIV) Infection: Current Knowledge, Implications, and Future Directions. Alcohol Clin Exp Res 2016; 40:2056-2072. [PMID: 27696523 PMCID: PMC5119641 DOI: 10.1111/acer.13204] [Citation(s) in RCA: 222] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Accepted: 07/28/2016] [Indexed: 12/20/2022]
Abstract
Alcohol use is common among people living with human immunodeficiency virus (HIV). In this narrative review, we describe literature regarding alcohol's impact on transmission, care, coinfections, and comorbidities that are common among people living with HIV (PLWH), as well as literature regarding interventions to address alcohol use and its influences among PLWH. This narrative review identifies alcohol use as a risk factor for HIV transmission, as well as a factor impacting the clinical manifestations and management of HIV. Alcohol use appears to have additive and potentially synergistic effects on common HIV-related comorbidities. We find that interventions to modify drinking and improve HIV-related risks and outcomes have had limited success to date, and we recommend research in several areas. Consistent with Office of AIDS Research/National Institutes of Health priorities, we suggest research to better understand how and at what levels alcohol influences comorbid conditions among PLWH, to elucidate the mechanisms by which alcohol use is impacting comorbidities, and to understand whether decreases in alcohol use improve HIV-relevant outcomes. This should include studies regarding whether state-of-the-art medications used to treat common coinfections are safe for PLWH who drink alcohol. We recommend that future research among PLWH include validated self-report measures of alcohol use and/or biological measurements, ideally both. Additionally, subgroup variation in associations should be identified to ensure that the risks of particularly vulnerable populations are understood. This body of research should serve as a foundation for a next generation of intervention studies to address alcohol use from transmission to treatment of HIV. Intervention studies should inform implementation efforts to improve provision of alcohol-related interventions and treatments for PLWH in healthcare settings. By making further progress on understanding how alcohol use affects PLWH in the era of HIV as a chronic condition, this research should inform how we can mitigate transmission, achieve viral suppression, and avoid exacerbating common comorbidities of HIV and alcohol use and make progress toward the 90-90-90 goals for engagement in the HIV treatment cascade.
Collapse
Affiliation(s)
- Emily C Williams
- Veterans Health Administration (VA) Health Services Research and Development, Center of Innovation for Veteran-Centered and Value-Driven Care, Seattle, Washington.,Department of Health Services, University of Washington, Seattle, Washington
| | - Judith A Hahn
- Departments of Medicine and Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, California
| | - Richard Saitz
- Department of Community Health Sciences, Boston University School of Public Health, Boston, Massachusetts.,Clinical Addiction Research and Education (CARE) Unit, Section of General Internal Medicine, Department of Medicine, Boston Medical Center, Boston University School of Medicine, Boston, Massachusetts
| | - Kendall Bryant
- Consortiums for HIV/AIDS and Alcohol Research Translation (CHAART) National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland
| | - Marlene C Lira
- Clinical Addiction Research and Education (CARE) Unit, Section of General Internal Medicine, Department of Medicine, Boston Medical Center, Boston University School of Medicine, Boston, Massachusetts
| | - Jeffrey H Samet
- Department of Community Health Sciences, Boston University School of Public Health, Boston, Massachusetts. .,Clinical Addiction Research and Education (CARE) Unit, Section of General Internal Medicine, Department of Medicine, Boston Medical Center, Boston University School of Medicine, Boston, Massachusetts.
| |
Collapse
|
8
|
Marrazzo JM, del Rio C, Holtgrave DR, Cohen MS, Kalichman SC, Mayer KH, Montaner JSG, Wheeler DP, Grant RM, Grinsztejn B, Kumarasamy N, Shoptaw S, Walensky RP, Dabis F, Sugarman J, Benson CA. HIV prevention in clinical care settings: 2014 recommendations of the International Antiviral Society-USA Panel. JAMA 2014; 312:390-409. [PMID: 25038358 PMCID: PMC6309682 DOI: 10.1001/jama.2014.7999] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
IMPORTANCE Emerging data warrant the integration of biomedical and behavioral recommendations for human immunodeficiency virus (HIV) prevention in clinical care settings. OBJECTIVE To provide current recommendations for the prevention of HIV infection in adults and adolescents for integration in clinical care settings. DATA SOURCES, STUDY SELECTION, AND DATA SYNTHESIS Data published or presented as abstracts at scientific conferences (past 17 years) were systematically searched and reviewed by the International Antiviral (formerly AIDS) Society-USA HIV Prevention Recommendations Panel. Panel members supplied additional relevant publications, reviewed available data, and formed recommendations by full-panel consensus. RESULTS Testing for HIV is recommended at least once for all adults and adolescents, with repeated testing for those at increased risk of acquiring HIV. Clinicians should be alert to the possibility of acute HIV infection and promptly pursue diagnostic testing if suspected. At diagnosis of HIV, all individuals should be linked to care for timely initiation of antiretroviral therapy (ART). Support for adherence and retention in care, individualized risk assessment and counseling, assistance with partner notification, and periodic screening for common sexually transmitted infections (STIs) is recommended for HIV-infected individuals as part of care. In HIV-uninfected patients, those persons at high risk of HIV infection should be prioritized for delivery of interventions such as preexposure prophylaxis and individualized counseling on risk reduction. Daily emtricitabine/tenofovir disoproxil fumarate is recommended as preexposure prophylaxis for persons at high risk for HIV based on background incidence or recent diagnosis of incident STIs, use of injection drugs or shared needles, or recent use of nonoccupational postexposure prophylaxis; ongoing use of preexposure prophylaxis should be guided by regular risk assessment. For persons who inject drugs, harm reduction services should be provided (needle and syringe exchange programs, supervised injection, and available medically assisted therapies, including opioid agonists and antagonists); low-threshold detoxification and drug cessation programs should be made available. Postexposure prophylaxis is recommended for all persons who have sustained a mucosal or parenteral exposure to HIV from a known infected source and should be initiated as soon as possible. CONCLUSIONS AND RELEVANCE Data support the integration of biomedical and behavioral approaches for prevention of HIV infection in clinical care settings. A concerted effort to implement combination strategies for HIV prevention is needed to realize the goal of an AIDS-free generation.
Collapse
Affiliation(s)
| | | | - David R Holtgrave
- The Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | | | | | | | | | | | | | - Beatriz Grinsztejn
- Evandro Chagas Clinical Research Institute (IPEC)-FIOCRUZ, Rio de Janeiro, Brazil
| | - N Kumarasamy
- YR Gaitonde Centre for AIDS Research and Education, Chennai, India
| | | | | | | | | | | |
Collapse
|
9
|
Kalichman SC, Zohren L, Eaton LA. Setting the bar high or setting up to fail? Interpretations and implications of the EXPLORE Study (HPTN 015). AIDS Behav 2014; 18:625-33. [PMID: 23989823 DOI: 10.1007/s10461-013-0603-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Controlled studies show that HIV risk reduction counseling significantly increases condom use, reduces unprotected sex and prevents sexually transmitted infections. Nevertheless, without evidence of reducing HIV incidence, these interventions are generally discarded. One trial, the EXPLORE study, was designed to test whether ten sessions of risk reduction counseling could impact HIV incidence among men who have sex with men in six US cities. Based on epidemiologic models to define effective HIV vaccines, a 35 % reduction in HIV incidence was set a priori as the benchmark of success in this behavioral intervention trial. Results demonstrated a significant effect of the intervention, with more than a 35 % reduction in HIV incidence observed during the initial 12-18 months following counseling. Over an unprecedented 48-month follow-up, however, the effect of counseling on HIV incidence declined to 18 %. The current review examined how the scientific literature has thus far judged the outcomes of the EXPLORE study as well as the policy implications of these judgments. We identified 127 articles that cited the EXPLORE study since its publication. Among articles that discuss the HIV incidence outcomes, 20 % judged the intervention effective and 80 % judged the intervention ineffective. The overwhelmingly negative interpretation of the EXPLORE study outcomes is reflected in public policies and prevention planning. We conclude that using a vaccine standard to define success led to a broad discrediting of the benefits of behavioral counseling and, ultimately, adversely impacted policies critical to the field of HIV prevention.
Collapse
Affiliation(s)
- Seth C Kalichman
- Department of Psychology, University of Connecticut, 406 Babbidge Road, Storrs, CT, 06269, USA,
| | | | | |
Collapse
|
10
|
Abstract
Two rather surprising anomalies relating to statistical power occur in testing mediation. First, in a model with no direct effect for which the total effect and indirect effect are identical, the power for the test of the total effect can be dramatically smaller than the power for the test of the indirect effect. Second, when there is a direct effect of a causal variable on the outcome controlling for the mediator, the power of the test of the indirect effect is often considerably greater than the power of the test of the direct effect, even when the two are of the same magnitude. We try to explain the reasons for these anomalies and how they affect practice.
Collapse
|