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Background: We recently showed that alcohol and cannabis can interact prenatally, and in a recent review paper, we identified parvalbumin‐positive (PV) interneurons in the hippocampus as a potential point of convergence for these teratogens. Methods: A 2 (Ethanol [EtOH], Air) × 2 (tetrahydrocannabinol [THC], Vehicle) design was used to expose pregnant Sprague‐Dawley rats to either EtOH or air, in addition to either THC or the inhalant vehicle solution, during gestational days 5–20. Immunohistochemistry was performed to detect PV interneurons in 1 male and 1 female pup from each litter at postnatal day 70. Results: Significant between‐group and subregion‐specific effects were found in the dorsal cornu ammonis 1 (CA1) subfield and the ventral dentate gyrus (DG). In the dorsal CA1 subfield, there was an increase in the number of PV interneurons in both the EtOH and EtOH +THC groups, but a decrease with THC alone. There were fewer changes in interneuron numbers overall in the DG, though there was a sex difference, with a decrease in the number of PV interneurons in the THC‐exposed group in males. There was also a greater cell layer volume in the DG in the EtOH +THC group than the control group, and in the CA1 region in the EtOH group compared to the control and THC groups. Conclusions: Prenatal exposure to alcohol and THC differentially affects parvalbumin‐positive interneuron numbers in the hippocampus, indicating that both individual and combined exposure can impact the balance of excitation and inhibition in a structure critically involved in learning and memory processes. [ABSTRACT FROM AUTHOR]

Background: Simultaneous use of alcohol and cannabis to enhance each other's effect can cause potential harm. Time trends are diverging in adolescent use of alcohol, which is declining, and cannabis, which is increasing among certain subgroups. However, little is known about trends in their simultaneous and non‐simultaneous use. Racial and socioeconomic disparities are emerging in cannabis use, which may portend consequences to public health. Methods: The 2000 to 2020 Monitoring the Future surveys included approximately 38,000 U.S. 12th‐grade students with information on simultaneous use and pertinent demographic factors. A 5‐level alcohol/cannabis measure included past‐year simultaneous use (i.e., alcohol and cannabis use at the same time), non‐simultaneous alcohol and cannabis use, alcohol‐use‐only, cannabis‐use‐only, and no use. Multinomial logistic regressions estimated associations (adjusted relative risk ratios; aRRR) with time period (2000 to 2004, 2005 to 2009, 2010 to 2014, 2015 to 2020). Models were adjusted and included interactions with sex, race/ethnicity, and parental education. Results: Between 2000 and 2020, simultaneous alcohol/cannabis use among 12th graders decreased from 24.4% to 18.7%. From 2015 to 2020 compared to 2000 to 2004, the odds of simultaneous use (adjusted relative risk ratio (aRRR) vs. no use = 0.57, 95% CI [0.50, 0.66]) and alcohol‐use‐only (aRRR = 0.55, 95% CI [0.49, 0.61]) decreased, while cannabis‐use‐only odds increased (aRRR = 2.59, 95% CI [1.87, 3.59]). Notably, the prevalence of cannabis‐use‐only more than doubled from 2011 to 2019. The odds of simultaneous use, alcohol‐use‐only, and non‐simultaneous use of alcohol and cannabis declined more rapidly among males than females, whereas the odds for cannabis‐use‐only increased faster for females than males. Increases in cannabis‐use‐only were faster for non‐white adolescents. Conclusion: Simultaneous use of alcohol and cannabis is declining among U.S. adolescents, but the decline is slower among females than males. Declines in simultaneous use are largely concomitant with historical declines in alcohol use, indicating that a continued focus on reducing alcohol use among adolescents and young adults has extended benefits to other adolescent substance use. However, cannabis use without any reported past‐year alcohol use more than doubled in the last decade, a concerning trend. [ABSTRACT FROM AUTHOR]

Background: Research conducted during the COVID‐19 Pandemic has identified two co‐occurring public health concerns: loneliness and substance use. Findings from research conducted prior to the pandemic are inconclusive as to the links between loneliness and substance use. This study aimed to measure associations of loneliness with three different types of substance use during COVID‐19: daily number of alcoholic drinks, cannabis use, and non‐cannabis drug use. Method: Data were obtained between October 2020 and May 2021 from 2,648 US adults (Mage = 38.76, 65.4% women) diverse with respect to race and ethnicity using online recruitment. Participants completed baseline surveys and daily assessments for 30 days. A daily loneliness measure was recoded into separate within‐ and between‐person predictor variables. Daily outcome measures included the number of alcoholic drinks consumed and dichotomous cannabis and non‐cannabis drug use variables. Generalized linear multilevel models (GLMLM) were used to examine within‐ and between‐person associations between loneliness and substance use. Results: The unconditional means model indicated that 59.0% of the variance in the daily number of alcoholic drinks was due to within‐person variability. GLMLM analyses revealed that, overall, people drank more on days when they felt a particularly high or particularly low degree of loneliness (positive quadratic effect). There was a negative and significant within‐person association between daily loneliness and the likelihood of cannabis use. There was also a positive and significant within‐person association between daily loneliness and the likelihood of non‐cannabis drug use. Conclusions: Associations between loneliness and substance use vary with substance type and whether within‐ or between‐person differences are assessed. These findings are relevant to the persistence of substance use disorders and thus of potential clinical importance. Individuals who do not experience severe loneliness at intake but who show daily increases in loneliness above baseline levels are at heightened risk of alcohol and non‐cannabis drug use. Future research could profitably examine just‐in‐time adaptive interventions that assess fluctuations in loneliness to prevent the development or exacerbation of substance use disorders. [ABSTRACT FROM AUTHOR]

Background: The majority of adolescents and young adults (AYA) who use cannabis also use alcohol. Although cannabis use is increasing in the United States (US), it is not known whether the increase contributes to either increased co‐use of alcohol and cannabis (e.g., complementarity) or replacement of alcohol with cannabis (e.g., substitution). The current study estimated the prevalence of alcohol use by cannabis use status among US AYA ages 12 to 25 in 2018 and trends in alcohol use by cannabis use status from 2002 to 2018. Methods: Data were drawn from the 2002 to 2018 National Survey on Drug Use and Health public use data files. The analytic sample included AYA ages 12 to 25 (2018 sample, n = 26,924; total combined sample 2002 to 2018, n = 576,053). Linear and logistic regression models were used to estimate past‐month alcohol use, daily alcohol use, and average quantity of alcohol consumed among AYA with and without past‐month cannabis use from 2002 to 2018. Results: In 2018, any alcohol use and daily alcohol use were significantly more common among AYA who used cannabis use than those who did not use cannabis. Overall, any alcohol use, daily alcohol use, and average drinks per day declined from 2002 to 2018 among AYA irrespective of recent cannabis use. However, the decline in any alcohol use, daily alcohol use, and average alcohol drinks per day was more rapid among AYA who used cannabis (daily and nondaily) than those who did not use cannabis. The rate of decline in average alcohol drinks per day was also higher among AYA with daily compared to nondaily cannabis use. Conclusions: Even with declines in alcohol use over time, drinking is much more common among AYA who report cannabis than those without recent cannabis use, which is consistent with complementarity. Yet, because the decline in alcohol use has been more rapid among AYA who use cannabis, there is also evidence of substitution. Thus, the current data on alcohol and cannabis use are consistent with both complementarity and substitution. However, these relationships may change as cannabis legalization expands over time. [ABSTRACT FROM AUTHOR]