Cohort profile: The Corona Behavioral Unit cohort, a longitudinal mixed-methods study on COVID-19-related behavior, well-being and policy support in the Netherlands.

This 'cohort profile' aims to provide a description of the study design, methodology, and baseline characteristics of the participants in the Corona Behavioral Unit cohort. This cohort was established in response to the COVID-19 pandemic by the Dutch National Institute for Public Health and the Environment (RIVM) and the regional public health services. The aim was to investigate adherence of and support for COVID-19 prevention measures, psychosocial determinants of COVID-19 behaviors, well-being, COVID-19 vaccination, and media use. The cohort also examined specific motivations and beliefs, such as for vaccination, which were collected through either closed-ended items or open text responses. In April 2020, 89,943 participants aged 16 years and older were recruited from existing nation-wide panels. Between May 2020 and September 2022, 99,676 additional participants were recruited through online social media platforms and mailing lists of higher education organizations. Participants who consented were initially invited every three weeks (5 rounds), then every six weeks (13 rounds), and since the summer of 2022 every 12 weeks (3 rounds). To date, 66% of participants were female, 30% were 39 years and younger, and 54% completed two or more questionnaires, with an average of 9.2 (SD = 5.7) questionnaires. The Corona Behavioral Unit COVID-19 cohort has published detailed insights into longitudinal patterns of COVID-19 related behaviors, support of COVID-19 preventive measures, as well as peoples' mental wellbeing in relation to the stringency of these measures. The results have informed COVID-19 policy making and pandemic communication in the Netherlands throughout the COVID-19 pandemic. The cohort data will continuously be used to examine COVID-19 related outcomes for scientific analyses, as well as to inform future pandemic preparedness plans.

General Mental Health, Loneliness, and Life Satisfaction in the Context of COVID-19 Policies: A 2-Year Cohort Study in the Netherlands, April 2020-January 2022.

OBJECTIVE: Although the COVID-19 pandemic has affected mental health, understanding who has been affected most and why is incomplete. We sought to understand changes in mental health in the context of transmission numbers and pandemic (social) restrictions and whether changes in mental health varied among population groups. METHODS: We analyzed data from 92 062 people (aged ≥16 years and able to read Dutch) who participated in the Corona Behavioral Unit cohort study at the National Institute for Public Health and the Environment, the Netherlands, from April 17, 2020, through January 25, 2022. Participants self-reported mental well-being through multiple rounds of surveys. We used a multivariable linear mixed-effects model to analyze loneliness, general mental health, and life satisfaction. RESULTS: As strictness of pandemic prevention measures and social restrictions increased, people's feelings of loneliness increased and mental health and life satisfaction decreased. As restrictions were relaxed, loneliness decreased and general mental health improved. Younger people (aged 16-24 y) versus older people (aged ≥40 y), people with low (vs high) education levels, and people living alone (vs living together) were more likely to have negative well-being outcomes. We observed that trajectories over time differed considerably only by age, with participants aged 16-24 years affected substantially more than participants aged ≥40 years by pandemic social restrictions. These patterns were consistent across multiple waves of SARS-CoV-2 infection. CONCLUSIONS: Our findings suggest that the social restrictions imposed by the Dutch government during the study period were associated with reduced mental well-being, especially among younger people. However, people appeared resilient as they recovered during periods when restrictions were relaxed. Monitoring and supporting well-being, in particular to reduce loneliness, may help younger people during periods of intense social restrictions.

Understanding public support for COVID-19 pandemic mitigation measures over time: Does it wear out?

Background: COVID-19 mitigation measures intend to protect public health, but their adverse psychological, social, and economic effects weaken public support. Less favorable trade-offs may especially weaken support for more restrictive measures. Support for mitigation measures may also differ between population subgroups who experience different benefits and costs, and decrease over time, a phenomenon termed "pandemic fatigue." Methods: We examined self-reported support for COVID-19 mitigation measures in the Netherlands over 12 consecutives waves of data collection between April 2020 and May 2021 in an open population cohort study. Participants were recruited through community panels of the 25 regional public health services, and through links to the online surveys advertised on social media. The 54,010 unique participants in the cohort study on average participated in 4 waves of data collection. Most participants were female (65%), middle-aged [57% (40-69 years)], highly educated (57%), not living alone (84%), residing in an urban area (60%), and born in the Netherlands (95%). Results: COVID-19 mitigation measures implemented in the Netherlands remained generally well-supported over time [all scores >3 on 5-point scale ranging 1 (low)-5 (high)]. During the whole period studied, support was highest for personal hygiene measures, quarantine and wearing face masks, high but somewhat lower for not shaking hands, testing and self-isolation, and restricting social contacts, and lowest for limiting visitors at home, and not traveling abroad. Women and higher educated people were more supportive of some mitigation measures than men and lower educated people. Older people were more supportive of more restrictive measures than younger people, and support for more socially restrictive measures decreased most over time in higher educated people or in younger people. Conclusions: This study found no support for pandemic fatigue in terms of a gradual decline in support for all mitigation measures in the first year of the pandemic. Rather, findings suggest that support for mitigation measures reflects a balancing of benefits and cost, which may change over time, and differ between measures and population subgroups.

Incidence of HIV and hepatitis C virus among people who inject drugs, and associations with age and sex or gender: a global systematic review and meta-analysis.

BACKGROUND: Measuring the incidence of HIV and hepatitis C virus (HCV) infection among people who inject drugs (PWID) is key to track progress towards elimination. We aimed to summarise global data on HIV and primary HCV incidence among PWID and associations with age and sex or gender. METHODS: In this systematic review and meta-analysis, we updated an existing database of HIV and HCV incidence studies among PWID by searching MEDLINE, Embase, and PsycINFO, capturing studies published between Jan 1, 2000, and Dec 12, 2022, with no language or study design restrictions. We contacted authors of identified studies for unpublished or updated data. We included studies that estimated incidence by longitudinally re-testing people at risk of infection or by using assays for recent infection. We pooled incidence and relative risk (RR; young [generally defined as ≤25 years] vs older PWID; women vs men) estimates using random-effects meta-analysis and assessed risk of bias with a modified Newcastle-Ottawa scale. This study is registered with PROSPERO, CRD42020220884. FINDINGS: Our updated search identified 9493 publications, of which 211 were eligible for full-text review. An additional 377 full-text records from our existing database and five records identified through cross-referencing were assessed. Including 28 unpublished records, 125 records met the inclusion criteria. We identified 64 estimates of HIV incidence (30 from high-income countries [HICs] and 34 from low-income or middle-income countries [LMICs]) and 66 estimates of HCV incidence (52 from HICs and 14 from LMICs). 41 (64%) of 64 HIV and 42 (64%) of 66 HCV estimates were from single cities rather than being multi-city or nationwide. Estimates were measured over 1987-2021 for HIV and 1992-2021 for HCV. Pooled HIV incidence was 1·7 per 100 person-years (95% CI 1·3-2·3; I2=98·4%) and pooled HCV incidence was 12·1 per 100 person-years (10·0-14·6; I2=97·2%). Young PWID had a greater risk of HIV (RR 1·5, 95% CI 1·2-1·8; I2=66·9%) and HCV (1·5, 1·3-1·8; I2=70·6%) acquisition than older PWID. Women had a greater risk of HIV (RR 1·4, 95% CI 1·1-1·6; I2=55·3%) and HCV (1·2, 1·1-1·3; I2=43·3%) acquisition than men. For both HIV and HCV, the median risk-of-bias score was 6 (IQR 6-7), indicating moderate risk. INTERPRETATION: Although sparse, available HIV and HCV incidence estimates offer insights into global levels of HIV and HCV transmission among PWID. Intensified efforts are needed to keep track of the HIV and HCV epidemics among PWID and to expand access to age-appropriate and gender-appropriate prevention services that serve young PWID and women who inject drugs. FUNDING: Canadian Institutes of Health Research, Fonds de recherche du Québec-Santé, Canadian Network on Hepatitis C, UK National Institute for Health and Care Research, and WHO.

Comprehensive needle and syringe program and opioid agonist therapy reduce HIV and hepatitis c virus acquisition among people who inject drugs in different settings: A pooled analysis of emulated trials.

BACKGROUND AND AIMS: Although the Netherlands, Canada and Australia were early adopters of harm reduction for people who inject drugs (PWID), their respective HIV and hepatitis C (HCV) epidemics differ. We measured the pooled effect of needle and syringe program (NSP) and opioid agonist therapy (OAT) participation on HIV and HCV incidence in these settings. DESIGN: For each cohort, we emulated the design and statistical analysis of a target trial using observational data. SETTING AND PARTICIPANTS: We included PWID at risk of HIV or HCV infection from the Amsterdam Cohort Studies (1985-2013), Vancouver Injection Drug Users Study (1997-2009) and Melbourne Injecting Drug User Cohort Study (SuperMIX) (2010-2021). MEASUREMENTS: Separately for each infection and cohort (only HCV in SuperMIX), marginal structural models were used to compare the effect of comprehensive (on OAT and 100% NSP coverage or on OAT only if no recent injection drug use) versus no/partial NSP/OAT (no OAT and/or <100% NSP coverage) participation. Pooled hazard ratios (HR) and 95% CI were calculated using random-effects meta-analysis. FINDINGS: We observed 94 HIV seroconversions and 81 HCV seroconversions among 2023 and 430 participants, respectively. Comprehensive NSP/OAT led to a 41% lower risk of HIV acquisition (pooled HR = 0.59, 95% CI = 0.36-0.96) and a 76% lower risk of HCV acquisition (pooled HR = 0.24, 95% CI = 0.11-0.51), compared with no/partial NSP/OAT, with little heterogeneity between studies for both infections (I2  = 0%). CONCLUSIONS: In the Netherlands, Canada and Australia, comprehensive needle and syringe program and opioid agonist therapy participation appears to substantially reduce HIV and hepatitis C acquisition compared with no or partial needle and syringe program/opioid agonist therapy participation. These findings from an emulated trial design reinforce the critical role of comprehensive access to harm reduction in optimizing infection prevention for people who inject drugs.

Randomised controlled trial of active case management to link hepatitis C notifications to treatment in Tasmania, Australia: a study protocol.

INTRODUCTION: By subsidising access to direct acting antivirals (DAAs) for all people living with hepatitis C (HCV) in 2016, Australia is positioned to eliminate HCV as a public health threat. However, uptake of DAAs has declined over recent years and new initiatives are needed to engage people living with HCV in care. Active follow-up of HCV notifications by the health department to the notifying general practitioner (GP) may increase treatment uptake. In this study, we explore the impact of using hepatitis C notifications systems to engage diagnosing GPs and improve patient access to treatment. METHODS AND ANALYSIS: This study is a randomised controlled trial comparing enhanced case management of HCV notifications with standard of care. The intervention includes phone calls from a department of health (DoH) specialist HCV nurse to notifying GPs and offering HCV management support. The level of support requested by the GP was graded in complexity: level 1: HCV information only; level 2: follow-up testing advice; level 3: prescription support including linkage to specialist clinicians and level 4: direct patient contact. The study population includes all GPs in Tasmania who notified HCV diagnosis to the DoH between September 2020 and December 2021. The primary outcome is proportion of HCV cases who initiate DAAs after 12 weeks of HCV notification to the health department. Secondary outcomes are proportion of HCV notifications that complete HCV RNA testing, treatment workup and treatment completion. Multiple logistic regression modelling will explore factors associated with the primary and secondary outcomes. The sample size required to detect a significant difference for the primary outcome is 85 GPs in each arm with a two-sided alpha of 0.05% and 80% power. ETHICS AND DISSEMINATION: The study was approved by University of Tasmania's Human Research Ethics Committee (Protocol ID: 18418) on 17 December 2019. Results of the project will be presented in scientific meetings and published in peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT04510246. TRIAL PROGRESSION: The study commenced recruitment in September 2020 and end of study expected December 2021.

The association between depression and oral health related quality of life in people who inject drugs.

BACKGROUND AND AIMS: Oral health related quality of life (OHRQoL) is known to be reduced in disadvantaged populations, including people who inject drugs. Mental health issues, such as depression are also commonly reported. In this study we examined the association between depression and OHRQoL. METHODS: Cross-sectional analysis survey data was collected from the Melbourne Injecting Drug User Cohort Study (SuperMIX) of people who inject drugs (N = 982). Three measures derived from the Oral Health Impact Profile (OHIP-14) were used to assess OHRQoL: Prevalence (reporting one or more dental issue "Very often" or "Fairly often" in the previous year), Extent (number of items reported either "Very often" or "Fairly often") and Severity (summary score of all ordinal responses). Regression analyses assessed the association between depression, indexed as scoring above 10 on the Patient Health Questionnaire (PHQ-9), and OHIP-14 measures, adjusted for sociodemographic, drug use and dental service utilisation variables. RESULTS: Overall, participants had low levels of OHRQoL, indexed through OHIP-14 scores (46% exhibiting prevalence, mean extent of 2.35 and mean severity of 12.72). Depression was associated with increases in all OHIP-14 measures, after adjustment for potential confounders. CONCLUSIONS: We found a significant association between depression and poor OHRQoL in this sample of people who inject drugs. Further research using a longitudinal frame is needed to determine the direction of this relationship. Interventions to improve oral health of people who inject drugs are urgently needed, and these may benefit mental health outcomes for people who inject drugs.

The Melbourne Safe Injecting Room Attracted People Most in Need of Its Service.

INTRODUCTION: In 2018, the first Medically Supervised Injecting Room in Melbourne, Australia was officially opened. This study assessed whether this facility attracted people who inject drugs, who were socially vulnerable, and who engaged in drug-related behaviors associated with increased morbidity and mortality risk. METHODS: This was a cross-sectional analysis of the frequency of Medically Supervised Injecting Room use during the first 18 months after opening (July 2018-December 2019) among 658 people who inject drugs participating in the Melbourne Injecting Drug User Cohort Study (SuperMIX). To examine the differences between no Medically Supervised Injecting Room use, infrequent use (<50% injections within the facility), and frequent use (≥50% of injections within the facility), RRRs were estimated using bivariate multinomial logistic regression analyses and postestimation Wald tests. Analyses were conducted in 2020. RESULTS: A total of 451 participants (68%) reported no Medically Supervised Injecting Room use, 142 (22%) reported infrequent use, and 65 (10%) reported frequent use. Participants who reported either infrequent or frequent use of the facility were more socially vulnerable (e.g., more often homeless) and more likely to report risky drug-related behaviors and poor health outcomes than those who reported no use. Participants who reported frequent use of the facility were also more likely to live close to the facility than those reporting infrequent use. CONCLUSIONS: The Melbourne Medically Supervised Injecting Room attracted socially marginalized people who inject drugs who are most at risk of harms related to injecting drug use and therefore who are most in need of the service. To determine the long-term impact use of this facility on key health outcomes such as overdose, future studies should consider the differences in vulnerability and risk behavior of people who inject drugs who use the Medically Supervised Injecting Room when examining the outcomes associated with the use of the facility.

Homelessness, unstable housing, and risk of HIV and hepatitis C virus acquisition among people who inject drugs: a systematic review and meta-analysis.

BACKGROUND: People who inject drugs (PWID) are at increased risk for HIV and hepatitis C virus (HCV) infection and also have high levels of homelessness and unstable housing. We assessed whether homelessness or unstable housing is associated with an increased risk of HIV or HCV acquisition among PWID compared with PWID who are not homeless or are stably housed. METHODS: In this systematic review and meta-analysis, we updated an existing database of HIV and HCV incidence studies published between Jan 1, 2000, and June 13, 2017. Using the same strategy as for this existing database, we searched MEDLINE, Embase, and PsycINFO for studies, including conference abstracts, published between June 13, 2017, and Sept 14, 2020, that estimated HIV or HCV incidence, or both, among community-recruited PWID. We only included studies reporting original results without restrictions to study design or language. We contacted authors of studies that reported HIV or HCV incidence, or both, but did not report on an association with homelessness or unstable housing, to request crude data and, where possible, adjusted effect estimates. We extracted effect estimates and pooled data using random-effects meta-analyses to quantify the associations between recent (current or within the past year) homelessness or unstable housing compared with not recent homelessness or unstable housing, and risk of HIV or HCV acquisition. We assessed risk of bias using the Newcastle-Ottawa Scale and between-study heterogeneity using the I2 statistic and p value for heterogeneity. FINDINGS: We identified 14 351 references in our database search, of which 392 were subjected to full-text review alongside 277 studies from our existing database. Of these studies, 55 studies met inclusion criteria. We contacted the authors of 227 studies that reported HIV or HCV incidence in PWID but did not report association with the exposure of interest and obtained 48 unpublished estimates from 21 studies. After removal of duplicate data, we included 37 studies with 70 estimates (26 for HIV; 44 for HCV). Studies originated from 16 countries including in North America, Europe, Australia, east Africa, and Asia. Pooling unadjusted estimates, recent homelessness or unstable housing was associated with an increased risk of acquiring HIV (crude relative risk [cRR] 1·55 [95% CI 1·23-1·95; p=0·0002]; I2= 62·7%; n=17) and HCV (1·65 [1·44-1·90; p<0·0001]; I2= 44·8%; n=28]) among PWID compared with those who were not homeless or were stably housed. Associations for both HIV and HCV persisted when pooling adjusted estimates (adjusted relative risk for HIV: 1·39 [95% CI 1·06-1·84; p=0·019]; I2= 65·5%; n=9; and for HCV: 1·64 [1·43-1·89; p<0·0001]; I2= 9·6%; n=14). For risk of HIV acquisition, the association for unstable housing (cRR 1·82 [1·13-2·95; p=0·014]; n=5) was higher than for homelessness (1·44 [1·13-1·83; p=0·0036]; n=12), whereas no difference was seen between these outcomes for risk of HCV acquisition (1·72 [1·48-1·99; p<0·0001] for unstable housing, 1·66 [1·37-2·00; p<0·0001] for homelessness). INTERPRETATION: Homelessness and unstable housing are associated with increased risk of HIV and HCV acquisition among PWID. Our findings support the development of interventions that simultaneously address homelessness and unstable housing and HIV and HCV transmission in this population. FUNDING: National Institute for Health Research, National Institute on Drug Abuse, National Institute of Allergy and Infectious Diseases, and Commonwealth Scholarship Commission.

Is Group Sex a Higher-Risk Setting for HIV and Other Sexually Transmitted Infections Compared With Dyadic Sex Among Men Who Have Sex With Men?

BACKGROUND: Group sex has been suggested as a potential high-risk setting for HIV and other sexually transmitted infections (STIs) among men who have sex with men (MSM). We investigated whether group sex is associated with lower condom use during anal sex and higher proportions of STIs compared with dyadic sex among HIV-negative MSM between 2009 and 2012. METHODS: Cross-sectional data from 7 data waves of the Amsterdam Cohort Studies were used. The sample consisted of 465 MSM who either reported both group and dyadic sex (at n = 706 visits) or dyadic sex only (at n = 1339 visits) in the preceding 6 months. Logistic regression with generalized estimating equations was used to investigate the association between sexual setting (group vs. dyadic sex), condomless anal sex, and STI. RESULTS: Group sex was reported at 35% (706/2045) of visits. Condomless sex was more often reported during dyadic than group sex (odds ratio, 3.64 95% confidence interval, 2.57-5.16). Men who had group sex were more likely diagnosed as having gonorrhea compared with men with dyadic sex (odds ratio, 1.71; 95% confidence interval, 1.08-2.97), but this effect was not retained in the multivariate model. CONCLUSIONS: Results demonstrate within-person differences in sexual behavior during group and dyadic sex among MSM. Men were more likely to use condoms during group sex than during dyadic sex. Thus, for some, group sex may not necessarily be risky for HIV infection compared with dyadic sex. However, group sex may be a higher-risk setting for acquiring STIs other than HIV, such as gonorrhea. Group sex encounters should be recognized as distinct sexual settings with specific risk characteristics that need to be addressed accordingly.

Is anyone around me using condoms? Site-specific condom-use norms and their potential impact on condomless sex across various gay venues and websites in The Netherlands.

OBJECTIVE: To investigate site-specific condom-use norms as assumed by visitors of gay venues and websites across The Netherlands and their association with men's own use of condoms. METHODS: In 2010, men who have sex with men (MSM) visiting 18 sex venues (e.g., saunas), 30 nonsex venues (e.g., bars), 6 dating websites, and 2 social network websites completed an on-site questionnaire measuring 2 site-specific norms concerning anal sex: descriptive (assumed condom use of others at venue or website) and injunctive (assumed approval of condom use by others at venue or website). We measured the association between assumed descriptive norms and own use of condoms using logistic regression. RESULTS: Among 2,376 participants (median age = 30 years; IQR = 22-43), 62% (n = 1,483) assumed that other visitors would not use condoms. Among men self-reporting on their own use of condoms, 22% (318/1,421) reported condomless anal sex. Men at nonsex venues assumed other visitors would use condoms more often and approved of using them more often compared to men at sex venues. At all sites (venues/websites), men who assumed that others did not use condoms were more likely to have condomless sex themselves. CONCLUSIONS: At gay sites across The Netherlands, more than half of MSM believed visitors of these sites would not use condoms during anal sex. The perception that others would not use condoms was associated with less own condom use. HIV prevention should address problematic on-site condom-use norms, as they play a role in influencing sexual behavior between men that meet at these sites.

Is serosorting effective in reducing the risk of HIV infection among men who have sex with men with casual sex partners?

BACKGROUND: We investigated the prevalence and protective value of serosorting [ie, establishing HIV concordance in advance to practice unprotected anal intercourse (UAI)] with casual partners (CP) among HIV-negative men who have sex with men (MSM) using longitudinal data from 2007 to 2011. METHODS: Men of the Amsterdam Cohort Studies were tested biannually for HIV-1 antibodies and filled in questionnaires about sexual behavior in the preceding 6 months. HIV incidence was examined among men who practiced UAI, UAI with serosorting, or consistent condom use, using Poisson regression. RESULTS: Of 445 MSM with CPs, 31 seroconverted for HIV during a total follow-up of 1107 person-years. Overall observed HIV incidence rate was 2.8/100 person-years. Consistent condom use was reported in 64%, UAI in 25%, and UAI with serosorting in 11% of the 2137 follow-up visits. MSM who practiced serosorting were less likely to seroconvert [adjusted incidence rate ratio (aIRR) = 0.46; 95% confidence interval (CI): 0.13 to 1.59] than MSM who had UAI, but more likely to seroconvert than MSM who consistently used condoms (aIRR = 1.32; 95% CI: 0.37 to 4.62), although differences in both directions were not statistically significant. MSM who consistently used condoms were less likely to seroconvert than MSM who had UAI (aIRR = 0.37; 95% CI: 0.18 to 0.77). DISCUSSION: The protective effect for serosorting we found was not statistically significant. Consistent condom use was found to be most protective against HIV infection. Larger studies are needed to demonstrate whether serosorting with CPs offers sufficient protection against HIV infection, and if not, why it fails to do so.

Undetectable viral load and the decision to engage in unprotected anal intercourse among HIV-positive MSM.

We investigated how often HIV-positive MSM (n = 177) decide to engage in unprotected anal intercourse (UAI) because they have an undetectable viral load (UVL). We found that 20-57% of the UAI acts were related to having UVL, varying by partner type and partner HIV status. Among HIV-concordant partners, consideration of UVL before engaging in UAI was more prevalent with sex buddies (55%) than with casual partners (20%), although marginally significant (p = 0.051). Among HIV-discordant partners, no significant difference was found in the frequency of UVL considerations before engaging in UAI: 40% with sex buddies versus 57% with casual partners. Interestingly, while the decision to engage in UAI based on UVL was frequently discussed with HIV-concordant partners (>91%), it was only discussed with HIV-discordant partners in 13-25% of the UAI cases (according to partner type), suggesting that the decision was mostly unilateral.

Serosorting and sexual risk behaviour according to different casual partnership types among MSM: the study of one-night stands and sex buddies.

Among HIV-negative men who have sex with men (MSM), any incident of unprotected anal intercourse (UAI) between casual partners is usually regarded as risky for HIV transmission. However, men are increasingly using knowledge of their casual partner's HIV-status to reduce HIV risk during UAI (i.e., serosorting). Since familiarity between casual partners may lead to higher levels of UAI and serosorting, we examined how often men have UAI and practice serosorting with three types of casual partnerships that differ in their degree of familiarity. We included 240 HIV-negative men of the Amsterdam Cohort Study among MSM. We distinguished three types of casual partnerships: one-night stand ("met by chance and had sex only once"); multiple-time casual partner ("met and had sex with several times") and the "regular" casual partner ("sex buddy"). Serosorting was defined as UAI with an HIV-concordant partner. Generalised estimating equations analyses were used to examine the association between type of casual partnership and sexual risk behaviour. Analyses revealed that men with a sex buddy were more likely to have UAI than men with a one-night stand (OR [95%CI] 2.39 [1.39-4.09]). However, men with a sex buddy were also more likely to practice serosorting than men with a one-night stand (OR [95%CI] 5.20 [1.20-22.52]). Men with a sex buddy had more UAI but also reported more serosorting than men with a one-night stand. As a result, the proportion of UAI without serosorting is lower for men with a sex buddy, and therefore men might have less UAI at risk for HIV with this partner type. However, the protective value of serosorting with a sex buddy against HIV transmission needs to be further established. At this time, we suggest that a distinction between the one-night stand and the sex buddy should be incorporated in future studies as men behave significantly different with the two partner types.

ERP correlates of source memory: unitized source information increases familiarity-based retrieval.

Source memory tests typically require subjects to make decisions about the context in which an item was encoded and are thought to depend on recollection of details from the study episode. Although it is generally believed that familiarity does not contribute to source memory, recent behavioral studies have suggested that familiarity may also support source recognition when item and source information are integrated, or "unitized," during study (Diana, Yonelinas, and Ranganath, 2008). However, an alternative explanation of these behavioral findings is that unitization affects the manner in which recollection contributes to performance, rather than increasing familiarity-based source memory. To discriminate between these possibilities, we conducted an event-related potential (ERP) study testing the hypothesis that unitization increases the contribution of familiarity to source recognition. Participants studied associations between words and background colors using tasks that either encouraged or discouraged unitization. ERPs were recorded during a source memory test for background color. The results revealed two distinct neural correlates of source recognition: a frontally distributed positivity that was associated with familiarity-based source memory in the high-unitization condition only and a parietally distributed positivity that was associated with recollection-based source memory in both the high- and low-unitization conditions. The ERP and behavioral findings provide converging evidence for the idea that familiarity can contribute to source recognition, particularly when source information is encoded as an item detail.