Professional Education

  • Doctor of Philosophy, University of California Los Angeles (2018)
  • Bachelor of Arts, Harvard University (2011)

All Publications

  • Association between medical cannabis laws and opioid overdose mortality has reversed over time. Proceedings of the National Academy of Sciences of the United States of America Shover, C. L., Davis, C. S., Gordon, S. C., Humphreys, K. 2019

    View details for DOI 10.1073/pnas.1903434116

    View details for PubMedID 31182592

  • Predictors of availability of long-acting medication for opioid use disorder. Drug and alcohol dependence Shover, C. L., Humphreys, K. 2019; 204: 107586


    The U.S. Food and Drug Administration has approved three long-acting medications for opioid use disorder (MOUD): extended-release naltrexone (XR-NTX) in 2010, a subdermal buprenorphine implant in 2016, and a depot buprenorphine injection in 2017. Long-acting MOUD options may improve adherence while reducing diversion, but their availability compared to daily-dosing MOUD has not been well-characterized. The objective of this analysis was to characterize the availability of long-acting MOUD in substance use disorder treatment settings in the United States.Using the 2017 National Survey on Substance Abuse Treatment Services (N-SSATS) and state-level opioid overdose mortality, we examined associations between state- and facility-level factors and offering long-acting MOUD, which included XR-NTX and the buprenorphine implant. We constructed multivariable mixed logistic regression models for both types of long-acting MOUD.Nationwide, 38% (n = 5141) of substance use treatment facilities provided any kind of MOUD (daily or long-acting). Of these, 62% provided XR-NTX, whereas only 3% offered the buprenorphine implant. Facilities in the East North Central, East South Central, West North Central and Mountain regions had higher odds of offering XR-NTX, as did federally-funded facilities, and facilities in states with the highest opioid overdose mortality rates.In 2017, XR-NTX was available at most of the minority of facilities offering MOUD, but the buprenorphine implant was not. Increasing the availability of MOUD, including long-acting options, is necessary to address unmet need for opioid use disorder treatment.

    View details for DOI 10.1016/j.drugalcdep.2019.107586

    View details for PubMedID 31593871

  • Six policy lessons relevant to cannabis legalization. The American journal of drug and alcohol abuse Shover, C. L., Humphreys, K. 2019: 1–9


    Cannabis (marijuana) has been legalized for recreational and/or medicinal use in many US states, despite remaining a Schedule-I drug at the federal level. As legalization regimes are established in multiple countries, public health professionals should leverage decades of knowledge from other policy areas (e.g., alcohol and tobacco regulation) to inform cannabis policy.Identify policy lessons from other more established policy areas that can inform cannabis policy in the United States, Canada, and any other nations that legalize recreational cannabis.Narrative review of policy and public health literature.We identified six key lessons to guide cannabis policy. To avoid the harms of "a medical system only in name," medical cannabis programs should either be regulated like medicine or combined with the recreational market. Capping potency of cannabis products can reduce the harms of the drug, including addiction. Pricing policies that promote public health may include minimum unit pricing or taxation by weight. Protecting science and public health from corporate interest can prevent the scenarios we have seen with soda and tobacco lobbies funding studies to report favorable results about their products. Legalizing states can go beyond reducing possession arrests (which can be accomplished without legalization) by expunging prior criminal records of cannabis-related convictions. Finally, facilitating rigorous research can differentiate truth from positive and negative hype about cannabis' effects.Scientists and policymakers can learn from the successes and failures of alcohol and tobacco policy to regulate cannabis products, thereby mitigating old harms of cannabis prohibition while reducing new harms from legalization.

    View details for PubMedID 30870053

  • Mind the gaps: prescription coverage and HIV incidence among patients receiving pre-exposure prophylaxis from a large federally qualified health center in Los Angeles, California : Mind the Gaps: Cobertura de recetas e incidencia de VIH entre pacientes recibiendo profilaxis pre-exposición de un centro de salud grande y federalmente calificado en Los Ángeles, CA. AIDS and behavior Shover, C. L., Shoptaw, S., Javanbakht, M., Lee, S. J., Bolan, R. K., Cunningham, N. J., Beymer, M. R., DeVost, M. A., Gorbach, P. M. 2019


    We conducted a records-based cohort study of patients who initiated pre-exposure prophylaxis (PrEP) at a large federally qualified health center in Los Angeles, CA to characterize patterns of PrEP use, identify correlates of PrEP discontinuation, and calculate HIV incidence. Of 3121 individuals initiating PrEP between 2014 and 2017, 42% (n = 1314) were active (i.e., had a current PrEP prescription) in April 2018. HIV incidence was 0.1/100 person-years among active PrEP patients, compared to 2.1/100 person-years among patients who discontinued. Compared to patients accessing PrEP through government programs with no prescription copay, risk of discontinuation was higher among those with private insurance (ARR = 1.4, 95% CI 1.2, 1.7), or no insurance (ARR = 4.5, 95% CI 3.2, 6.4). Sixty-three percent of active PrEP patients had gaps between PrEP prescriptions, averaging one gap per year (median length = 65 days). Increasing access to free or low-cost PrEP can improve PrEP continuity.

    View details for PubMedID 30953305

  • The relationship of Medicaid expansion to psychiatric comorbidity care within substance use disorder treatment programs. Journal of substance abuse treatment Shover, C. L., Abraham, A., D'Aunno, T., Friedmann, P. D., Humphreys, K. 2019; 105: 44–50


    Co-occurring mental health disorders are common among substance use disorder (SUD) patients. Medicaid expansion aimed to reduce barriers to SUD and mental health care and thereby improve treatment outcomes.We estimated change in the proportion of United States SUD treatment sites offering treatment for psychiatric comorbidities following Medicaid expansion as part of implementation of the Affordable Care Act (ACA) in 2014. Using panel data from the 2013-2014, n = 660, and 2016-2017, n = 638, waves of the National Drug Abuse Treatment System Survey (NDATSS), we estimated change in the proportion of sites offering antidepressant medication, other psychiatric medication, behavioral treatment, or any combination thereof for treatment of mental health comorbidities (i.e., beyond services focused on SUD). We modeled the impact of Medicaid expansion as an interaction between year and date of Medicaid expansion. We constructed a mixed-effects linear regression model for each outcome, with the interaction variable as the main exposure, site as a random effect, and site's average duration of treatment, proportion of clients with psychiatric comorbidities, average caseload per treatment prescribing-clinician on staff, type of facility and geographic region as covariates, to estimate a difference-in-differences (D-I-D) equation.The adjusted D-I-D analysis indicated that the proportion of SUD treatment sites offering antidepressants for psychiatric treatment increased 10% (95% CI 1%, 18%) in the Medicaid expansion sites compared to non-expansion sites. The D-I-D for other psychiatric medications was also 10% (95% 1%, 19%). No significant changes were observed in behavioral treatment or the combination measure. The strongest association between Medicaid expansion and offering medication for mental health comorbidities was the 34% increase observed for residential treatment settings (95% CI 10%, 59%).Availability of psychiatric medication treatment in SUD treatment settings increased following Medicaid expansion, particularly in residential SUD facilities. This policy change has facilitated integrated treatment for the substantial share of SUD treatment patients with mental health comorbidities, with the greatest benefit for patients receiving SUD treatment in residential programs.

    View details for DOI 10.1016/j.jsat.2019.07.012

    View details for PubMedID 31443890

  • HIV Preexposure Prophylaxis Initiation at a Large Community Clinic: Differences Between Eligibility, Awareness, and Uptake. American journal of public health Shover, C. L., Javanbakht, M., Shoptaw, S., Bolan, R. K., Lee, S. J., Parsons, J. T., Rendina, J., Gorbach, P. M. 2018: e1–e10


    To characterize uptake of HIV preexposure prophylaxis (PrEP) in a community setting and to identify disparities in PrEP use by demographic and behavioral factors associated with increased HIV risk.We conducted a cross-sectional study of 19 587 men who have sex with men and transgender people visiting a Los Angeles, California, clinic specializing in lesbian, gay, bisexual, and transgender care between August 2015 and February 2018 by using clinical care data.Seventy percent of patients met PrEP eligibility criteria, while 10% reported PrEP use. Using sex drugs, reporting both condomless anal intercourse and recent sexually transmitted infection, older age, and higher education level were associated with higher odds of PrEP use given eligibility. Latino or Asian race/ethnicity and bisexual orientation were associated with lower odds of PrEP use given eligibility. Higher odds of perceived need were associated with demographic risk factors but PrEP use was not similarly elevated.Discrepancies between PrEP eligibility, perceived need, and use reveal opportunities to improve PrEP delivery in community settings. Public Health Implications. Efforts are needed to facilitate PrEP uptake in populations with highest HIV incidence. (Am J Public Health. Published online ahead of print August 23, 2018: e1-e10. doi:10.2105/AJPH.2018.304623).

    View details for PubMedID 30138062

  • Using Sexual Orientation and Gender Identity to Monitor Disparities in HIV, Sexually Transmitted Infections, and Viral Hepatitis. American journal of public health Shover, C. L., DeVost, M. A., Beymer, M. R., Gorbach, P. M., Flynn, R. P., Bolan, R. K. 2018; 108 (S4): S277–S283


    To quantify sexual orientation and gender identity (SOGI) disparities in incidence of HIV, other sexually transmitted infections (STIs), and viral hepatitis.We performed a records-based study of 19 933 patients visiting a federally qualified health center in Los Angeles, California, between November 2016 and October 2017 that examined HIV, STIs, and viral hepatitis incidence proportions. We created multivariable logistic regression models to examine the association between incidence proportions and SOGI among people living with HIV and HIV-negative patients.Among those who were HIV-negative at baseline (n = 16 757), 29% tested positive for any STI during the study period, compared with 38% of people living with HIV. Stratified by birth sex, STI positivity was 32% among men and 11% among women. By SOGI, STI positivity was 35% among gay and bisexual cisgender men, 15% among heterosexual cisgender men, 11% among cisgender women, 25% among transgender women, 13% among gay and bisexual transgender men, 3% among heterosexual transgender men, and 26% among nonbinary people.Stratifying by SOGI highlighted disparities that are obscured when stratifying by birth sex. Public Health Implications. To monitor and reduce disparities, health jurisdictions should include SOGI data with infectious disease reporting.

    View details for PubMedID 30383431

  • HIVR4P 2018: From Research to Impact Conference Summary and Highlights AIDS RESEARCH AND HUMAN RETROVIRUSES Shacklett, B. L., Blanco, J., Hightow-Weidman, L., Mgodi, N., Alcami, J., Buchbinder, S., Chirenje, M., Dabee, S., Diallo, M., Dumchev, K., Herrera, C., Levy, M. E., Martin Gayo, E., Makoah, N., Mitchell, K. M., Mugwanya, K., Reddy, K., Luisa Rodriguez, M., Rodriguez-Garcia, M., Shover, C. L., Shrivastava, T., Tomaras, G., Van Diepen, M., Walia, M., Warren, M., Manrique, A., Thyagarajan, B., Torri, T. 2019
  • Associations Between Cannabis Use, Sexual Behavior, and Sexually Transmitted Infections/Human Immunodeficiency Virus in a Cohort of Young Men Who Have Sex With Men. Sexually transmitted diseases Gorbach, P. M., Javanbakht, M., Shover, C. L., Bolan, R. K., Ragsdale, A., Shoptaw, S. 2019; 46 (2): 105–11


    Among men who have sex with men (MSM) the relationship between sexually transmitted infections (STIs) and cannabis use is not well established. We assessed cannabis use, sexual behavior, and STIs including human immunodeficiency virus (HIV) in a diverse cohort of young MSM.In Los Angeles, the mSTUDY cohort conducted visits every 6 months with 512 MSM between 2014 and 2017 collecting demographics, sexual behaviors, and reports of frequency of substance use. Each visit conducted testing for gonorrhea, chlamydia, and syphilis via blood, urine, and pharyngeal and rectal swabs by PCR, Human immunodeficiency virus was assessed using rapid tests for HIV-negatives and viral load for HIV-positives. We analyzed the relationship between cannabis use, sexual behaviors and STIs/HIV across 1535 visits.Significantly fewer participants tested positive for STIs at visits when reporting the previous 6 months use of only cannabis (11.7%) compared with no drugs (16.3%) or other drugs (20.0%, P = 0.01). Fewer MSM reporting only cannabis use than no or other drug use had been incarcerated, had incarcerated partners, experienced interpersonal violence, and were HIV-positive. In multivariable analyses visits with positive STIs were associated with other drug use (adjusted odds ratio, 1.69; 95% confidence interval, 1.03-2.78) but not use of cannabis only or no drug use after controlling for age, HIV status, new sex partners, and number of sex partners.When MSM reported using cannabis exclusively fewer STIs were detected and lower risk sexual engagements reported than when MSM reported no drug or other drug use.

    View details for PubMedID 30640212

    View details for PubMedCentralID PMC6342487

  • App-Based Sexual Partner Seeking and Sexually Transmitted Infection Outcomes: A Cross-Sectional Study of HIV-Negative Men Who Have Sex With Men Attending a Sexually Transmitted Infection Clinic in Los Angeles, California SEXUALLY TRANSMITTED DISEASES DeVost, M. A., Beymer, M. R., Weiss, R. E., Shover, C. L., Bolan, R. K. 2018; 45 (6): 394–99


    Gay, bisexual, and other men who have sex with men (MSM) face higher rates of sexually transmitted infections (STIs) compared with the general population. The association between venues where sexual partners are met and STI transmission is dynamic and poorly understood, especially among those who use geosocial networking (GSN) apps. This study aimed to determine whether there is a difference in STI incidence between MSM who met their last sexual partner through a GSN app and MSM who met their last partner via other venues.Data were analyzed from HIV-negative MSM attending the Los Angeles LBGT Center between August 2015 and July 2016 (n = 9499). Logistic regression models were used to investigate the relationship between STI incidence and whether or not an individual met his last partner through a GSN app.No relationship was detected between STI incidence and whether one's last sexual partner was met via GSN app. However, an association was detected between STI incidence and having used GSN apps to meet sexual partners in the past 3 months. A dose-response relationship was observed between the number of venues used to meet partners and testing positive for any STI (adjusted odds ratio, 1.08; 95% confidence interval, 1.02-1.14).The relationship between how people meet sexual partners and STI acquisition is much more nuanced than previously thought. Geosocial networking apps do not inherently expose users to high-risk reservoirs of STIs, but further understanding of the complexity of sexual networks and networking methods is warranted, given increasing rates of STIs.

    View details for DOI 10.1097/OLQ.0000000000000770

    View details for Web of Science ID 000432705500010

    View details for PubMedID 29465675

    View details for PubMedCentralID PMC5948131

  • Tobacco-Free Policies and Tobacco Cessation Systems at Health Centers Serving Lesbian, Gay, Bisexual, and Transgender Clients LGBT HEALTH Lee, J. L., DeMarco, M. E., Beymer, M. R., Shover, C. L., Bolan, R. K. 2018; 5 (4): 264–69


    LGBT populations have high rates of tobacco use. Health centers serving LGBT clients are an important source of care. The researchers aimed to assess the implementation of recommended systems-level tobacco cessation interventions at these health centers.Using systematic searching, directories, and expert review, we identified health centers serving LGBT clients that provide primary care. We conducted phone-based, semi-structured interviews with administrators (n = 11) between September 2016 and March 2017 regarding implementation of the Clinical Practice Guideline, Treating Tobacco Use and Dependence: 2008 Update (the Guideline). Two authors confirmed saturation and two authors conducted thematic coding.Eight themes were identified, including clear evidence of systems-level procedures for asking about, advising on, and assessing tobacco use. Interviewees viewed tobacco use as important given existing disparities. However, there was room for improvement in the following areas: (1) Education for staff on tobacco cessation was ad hoc and not formalized; (2) materials and resources for tobacco cessation available in the center varied widely and changed when a staff champion arrived or left; (3) no point person was assigned to coordinate tobacco cessation efforts; and, (4) assessment of tobacco use as a vital sign is not consistent-some centers met meaningful use quality metrics (e.g., once or more in the past 24 months) instead of the Guideline recommendation (every visit). Addressing tobacco use competes with addressing other health risk behaviors.Administrators at health centers serving LGBT clients viewed tobacco use as an important issue. However, there was room for improvement in implementation of systems recommended in the Guideline. Targeted outreach is warranted to improve standardization of implementation and promote cessation of tobacco use.

    View details for PubMedID 29658846

  • Accuracy of Presumptive Gonorrhea Treatment for Gay, Bisexual, and Other Men Who Have Sex with Men: Results from a Large Sexual Health Clinic in Los Angeles, California LGBT HEALTH Shover, C. L., Beymer, M. R., Unger, E. M., Javanbakht, M., Bolan, R. K. 2018; 5 (2): 139–44


    This study analyzed the accuracy of presumptive gonorrhea treatment in a sexual health clinic serving primarily gay, bisexual, and other men who have sex with men (MSM). Treating suspected gonorrhea before laboratory confirmation can reduce symptoms and transmission; however, this strategy can overtreat uninfected individuals, which may promote antimicrobial resistance. We identified differences in accuracy of gonorrhea presumptive treatment by site of infection and presence of signs or symptoms.We conducted a cross-sectional study of gay, bisexual, and other MSM who were treated presumptively for gonorrhea at the Los Angeles LGBT Center between February and July 2015. We calculated positivity of treated patients, proportion of infections treated, and positive predictive value (PPV) of treating gonorrhea presumptively based on signs, symptoms, or exposure at the urethral, rectal, or pharyngeal site.Of 9141 testing visits, presumptive treatment was provided at 1677 (18%). Overall, gonococcal infections were identified at 31% (n = 527) of visits where presumptive treatment was provided, compared to 9% (n = 657) of visits without presumptive treatment (P < 0.01). Forty-five percent of gonococcal infections were treated presumptively, and treatment was provided at 14% of gonorrhea-negative visits. Seventy-eight percent of urethral, 54% of rectal, and 35% of pharyngeal infections were treated presumptively. PPV was highest for genitourinary signs.Approximately one-third of gay, bisexual, or other MSM treated presumptively for gonorrhea at a sexual health clinic tested positive for gonorrhea. These findings highlight the potential contribution of point-of-care tests in reducing overtreatment resulting from presumptive treatment.

    View details for PubMedID 29493405

    View details for PubMedCentralID PMC5833247

  • Does HIV pre-exposure prophylaxis use lead to a higher incidence of sexually transmitted infections? A case-crossover study of men who have sex with men in Los Angeles, California. Sexually transmitted infections Beymer, M. R., DeVost, M. A., Weiss, R. E., Dierst-Davies, R., Shover, C. L., Landovitz, R. J., Beniasians, C., Talan, A. J., Flynn, R. P., Krysiak, R., McLaughlin, K., Bolan, R. K. 2018


    Pre-exposure prophylaxis (PrEP) is an effective method for reducing HIV incidence among at-risk populations. However, concerns exist over the potential for an increase in STIs following PrEP initiation. The objective of this study is to compare the STI incidence before and after PrEP initiation within subjects among a cohort of men who have sex with men in Los Angeles, California.The present study used data from patients who initiated PrEP services at the Los Angeles LGBT Center between October 2015 and October 2016 (n=275). A generalised linear mixed model was used with a case-crossover design to determine if there was a significant difference in STIs within subjects 365 days before (before-PrEP period) and 365 days after PrEP initiation (after-PrEP period).In a generalised linear mixed model, there were no significant differences in urethral gonorrhoea (P=0.95), rectal gonorrhoea (P=0.33), pharyngeal gonorrhoea (P=0.65) or urethral chlamydia (P=0.71) between periods. There were modest increases in rectal chlamydia (rate ratio (RR) 1.83; 95% CI 1.13 to 2.98; P=0.01) and syphilis diagnoses (RR 2.97; 95% CI 1.23 to 7.18; P=0.02).There were significant increases in rectal chlamydia and syphilis diagnoses when comparing the periods directly before and after PrEP initiation. However, only 28% of individuals had an increase in STIs between periods. Although risk compensation appears to be present for a segment of PrEP users, the majority of individuals either maintain or decrease their sexual risk following PrEP initiation.

    View details for PubMedID 29487172

  • Concordance between self-reported STI history and biomedical results among men who have sex with men in Los Angeles, California SEXUALLY TRANSMITTED INFECTIONS Cunningham, N. J., Beymer, M. R., Javanbakht, M., Shover, C. L., Bolan, R. K. 2017; 93 (7): 514-+


    HIV studies and risk assessments among men who have sex with men (MSM) frequently use self-reported STI history as a proxy for true STI history. The objective of our study was to assess the validity of self-reported STI history through comparison with laboratory-confirmed biomedical results.Data were analysed for MSM attending the Los Angeles LGBT Center (the Center) from August 2011 to July 2015. We identified 10 529 unique MSM who received testing for chlamydia, gonorrhoea and/or syphilis and had a later visit in which they self-reported their STI history to a clinic counsellor during a risk assessment.MSM who had an STI in the past year self-reported their STI history with 51%-56% accuracy, and MSM who had an STI more than a year ago self-reported their STI history with 65%-72% accuracy. Among MSM with any positive STIs at the Center, black/African-American and Hispanic MSM were more likely to inaccurately self-report their positive results for gonorrhoea (adjusted OR (aOR): 1.48, 95% CI 1.09 to 2.01; aOR: 1.39, 95% CI 1.14 to 1.70). Additionally, HIV-positive MSM were more likely to inaccurately self-report their positive results for gonorrhoea (aOR: 1.63, 95% CI 1.22 to 2.18) and/or syphilis (aOR: 2.19, 95% CI 1.08 to 4.47).This is the first study that attempts to evaluate the validity of self-reported STI history among MSM. We found that self-reported STI history may not be an appropriate proxy for true STI history in certain settings and minority populations. Clinical guidelines and research studies that rely on self-reported STI history will need to modify their recommendations in light of the limited validity of these data.

    View details for PubMedID 28554893

    View details for PubMedCentralID PMC5815859

  • Are Partner Race and Intimate Partner Violence Associated with Incident and Newly Diagnosed HIV Infection in African-American Men Who Have Sex with Men? JOURNAL OF URBAN HEALTH-BULLETIN OF THE NEW YORK ACADEMY OF MEDICINE Beymer, M. R., Harawa, N. T., Weiss, R. E., Shover, C. L., Toynes, B. R., Meanley, S., Bolan, R. K. 2017; 94 (5): 666–75


    Black gay, bisexual, and other men who have sex with men (BMSM) experience a disparate rate of HIV infections among MSM. Previous analyses have determined that STI coinfection and undiagnosed HIV infection partly explain the disparity. However, few studies have analyzed the impact of partner-level variables on HIV incidence among BMSM. Data were analyzed for BMSM who attended the Los Angeles LGBT Center from August 2011 to July 2015 (n = 1974) to identify risk factors for HIV infection. A multivariable logistic regression was used to analyze predictors for HIV prevalence among all individuals at first test (n = 1974; entire sample). A multivariable survival analysis was used to analyze predictors for HIV incidence (n = 936; repeat tester subset). Condomless receptive anal intercourse at last sex, number of sexual partners in the last 30 days, and intimate partner violence (IPV) were significant partner-level predictors of HIV prevalence and incidence. Individuals who reported IPV had 2.39 times higher odds (CI 1.35-4.23) and 3.33 times higher hazard (CI 1.47-7.55) of seroconverting in the prevalence and incidence models, respectively. Reporting Black partners only was associated with increased HIV prevalence, but a statistically significant association was not found with incidence. IPV is an important correlate of both HIV prevalence and incidence in BMSM. Further studies should explore how IPV affects HIV risk trajectories among BMSM. Given that individuals with IPV history may struggle to negotiate safer sex, IPV also warrants consideration as a qualifying criterion among BMSM for pre-exposure prophylaxis (PrEP).

    View details for PubMedID 28616719

    View details for PubMedCentralID PMC5610124