Effects of caffeine on alcohol reinforcement: beverage choice, self-administration, and subjective ratings

Energy drinks, substance use, and posttraumatic stress symptoms among Palestinian athletes: the mediating role of perceived self-efficacy and resilience

The current study aimed to test the association between energy drinks, substance use, and posttraumatic stress symptoms, and the mediating role of perceived self-efficacy and resilience among Palestinian athletes. The sample of our study consisted of 480 Palestinian athletes: 160 women and 320 men, all were selected from five Palestinian universities located in the West Bank of Palestine. The findings of our study revealed that energy drinks positively correlated with substance abuse, and posttraumatic stress symptoms. In addition, a negative association was found between perceived self-efficacy, substance use, and posttraumatic stress symptoms. Moreover, a negative association was found between resilience, substance use, and posttraumatic stress symptoms. Results of Structural equation modeling (SEM) revealed that resilience and perceived self-efficacy mediated the association between energy drinks, substance use and posttraumatic stress symptoms. Our findings underline the importance of enhancing resilience and perceived self-efficacy among athletes to prevent initial substance use/misuse, as several traits found in resilient athletes such as high self-esteem, empathy, help-seeking, and self-awareness are important in deterring athletes from engaging in harmful substances like tobacco, marijuana, and alcohol.

Energy drinks and alcohol use among adolescents: A longitudinal study

BACKGROUND

Alcohol use is a leading cause of reduced health among young people. Consumption of energy drinks might be a risk factor for alcohol use. The aim of this study was to examine if more frequent consumption of energy drinks in early adolescence was associated with higher concurrent alcohol consumption, and with stronger increase in alcohol use throughout adolescence.

METHODS

The data came from MyLife, a longitudinal study where Norwegian adolescents completed e-questionnaires in the autumn of 2017, 2018, 2019, 2020, and 2021. The participants were a nationwide sample of 2916 adolescents (mean age: 14.25 [SD = 0.85], 56% girls). At baseline, adolescents self-reported how often they had consumed energy drinks over the past month, a range of family factors, individual characteristics, and substance use. Self-reports of alcohol use (frequency, usual quantity, and frequency of consuming five or more units) were collected at all five assessments and combined into continuous variables.

RESULTS

The results of fully adjusted growth curve models indicate that more frequent consumption of energy drinks at baseline was associated with greater concurrent alcohol use (p < .001), and greater increase in alcohol use over time (p < .05). The effect of energy drinks on concurrent alcohol use was stronger for girls, but the effect on increase over time was stronger for boys.

CONCLUSION

Consumption of energy drinks in early adolescence is associated with more alcohol use throughout adolescence, but the effect size was rather modest in this sample of Norwegian adolescents.

Alcohol mixed energy drink usage and risk-taking among college students in Western New York State

Alcohol mixed energy drinks (AmED) may promote excessive alcohol intake and risk-taking among college students. Objective: To understand the relationship between AmED use and risky behavior as well as attitudes and motivations for AmED use. Participants: Undergraduate college students N = 422 (Study 1), N = 37 (Study 2). Methods: Using a mixed-methods approach, we first surveyed undergraduate students about their AmED and alcohol consumption and a series of risk behaviors, self-efficacy, and beliefs (Study 1). We then conducted focus groups within the same population to better understand attitudes, knowledge, and motivations for using AmED (Study 2). Results: Recent AmED use was significantly associated with an increased number of reported binge drinking occasions and self-reported driving while intoxicated events. Our qualitative data analyses revealed two major themes associated with AmED consumption: factors encouraging AmED use and decisions about driving while under the influence of alcohol. Conclusions: These findings add to the literature of beliefs and motivations for AmED use among college students.

Caffeine modulates apoptosis, oxidative stress, and inflammation damage induced by tramadol in cerebellum of male rats

Tramadol, an opioid used as analgesic, can induce neurotoxic effects associated to cognitive dysfunction. Moreover, caffeine has been reported to have neuroprotective effects. In this regard, we hypothesized that administration of caffeine can modulate tramadol-induced damages in cerebellum. For this study, forty male Wistar rats were divided into four groups: the control group, the tramadol group (50mg/kg), the caffeine group (37.5mg/kg), and the tramadol+caffeine group (50mg/kg tramadol+37.5mg/kg caffeine). At the end of study (day 21), after performing rotarod behavioral test, cerebellum tissue samples were removed and prepared for further evaluations including biochemical profile markers (MDA, GPx, and SOD), immunohistochemistry for Caspase-3, as well as the expression of genes involved in cellular processes such as inflammation markers (IL-1β, HMGB1, IL-6, and TNF), apoptosis markers (Caspase-3, Caspase-8, Bax, and P21), and autophagy markers (LAMP2, ATG5, BECN1, and ATG12). Stereological evaluations were performed to determine the total volume of granular and molecular layers and white matter of cerebellum tissue and numerical density of the Purkinje cells. Our results showed that the stereological parameters, biochemical profiles (except MDA) and behavioral function were significantly higher in the tramadol+caffeine group compared to the tramadol group. Autophagy-related genes were significantly upregulated in tramadol+caffeine group compared to the tramadol group. While the expression of inflammatory and apoptosis genes, MDA level, as well as density of apoptosis cells were significantly lower in the tramadol+caffeine group compared to the tramadol group. Briefly, it can be concluded that administration of caffeine has neuroprotective effects in cerebellar damages induced by tramadol.

Caffeine increases alcohol self-administration, an effect that is independent of dopamine D2 receptor function

The rising popularity of alcohol mixed with energy drinks (AmEDs) has become a significant public health concern, with AmED users reporting higher levels of alcohol intake than non-AmED users. One mechanism proposed to explain this heightened level of alcohol intake in AmED users is that the high levels of caffeine found in energy drinks may increase the positive reinforcing properties of alcohol, an effect that may be dependent on interactions between adenosine receptor signaling pathways and the dopamine D₂ receptor. Therefore, the purpose of the current study was to confirm whether caffeine does increase the positive reinforcing effects of alcohol using both fixed ratio (FR) and progressive ratio (PR) designs, and to investigate a potential role of the dopamine D₂ receptor to caffeine-induced increases in alcohol self-administration. Male Long-Evans rats were trained to self-administer a sweetened alcohol solution (10% v/v alcohol + 2% w/v sucrose) on an FR2 schedule of reinforcement, and the effects of caffeine (0, 5, 10, and 20 mg/kg, i. p. [intraperitoneally]) on the maintenance of alcohol self-administration and alcohol break point were examined. Parallel experiments in rats trained to self-administer sucrose (0.8% w/v) were conducted to determine whether caffeine's reinforcement-enhancing effects extended to a non-drug reinforcer. Caffeine pretreatment (5-10 mg/kg) significantly increased sweetened alcohol self-administration and motivation for a sweetened alcohol reinforcer. However, similar increases in self-administration of a non-drug reinforcer were not observed. Contrary to our hypothesis, the D₂ receptor antagonist eticlopride did not block a caffeine-induced increase in sweetened alcohol self-administration, nor did it alter caffeine-induced increases in motivation for a sweetened alcohol reinforcer. Taken together, these results support the hypothesis that caffeine increases the positive reinforcing effects of alcohol, which may explain caffeine-induced increases in alcohol intake. However, the reinforcement-enhancing effects of caffeine appear to be independent of D₂ receptor function.

Association between energy drink consumption and substance use in adolescence: A systematic review of prospective cohort studies

BACKGROUND

It is unclear whether energy drink (ED) consumption is associated with substance use (SU) in adolescence. The purpose of this study is to clarify the association.

METHODS

A systematic review was conducted using a wide range of electronic bibliographic databases to search for published prospective cohort studies on the topic from inception to 14th August 2019. The risk of bias was addressed by using the Risk Of Bias In Non-randomised Studies - of Interventions; ROBINS-I. Studies targeting adolescents were collected. Additionally, we collected studies that examined an association between the extent of energy drink consumption as exposure variables and any substance use as outcome variables.

RESULTS

Five studies met the eligibility criteria. ED consumption was associated with adolescent use of alcohol, tobacco, cannabis, prescription stimulants, and analgesics. However, the overall risk of bias in the included studies was severe.

CONCLUSION

ED consumption may be associated with SU in adolescence, particularly alcohol use. The results, however, were still inconclusive due to the relatively low methodological quality in the included studies. Evidence from more well-designed trials is needed in future research.

Caffeine Potentiates Ethanol-Induced Neurotoxicity Through mTOR/p70S6K/4E-BP1 Inhibition in SH-SY5Y Cells

Caffeine is a popular psychostimulant, which is frequently consumed with ethanol. However, the effects of caffeine on neuronal cells constantly exposed to ethanol have not been investigated. Apoptosis and oxidative stress occurring in ethanol-induced neurotoxicity were previously associated with decreased phosphorylation of the mTOR/p70S6K/4E-BP1 signaling proteins. Evidence also suggested that caffeine inhibits the mTOR pathway. In this study, human SH-SY5Y neuroblastoma cells were exposed to caffeine after pretreatment for 24 hours with ethanol. Results indicated that both ethanol and caffeine caused neuronal cell death in a dose- and time-dependent manner. Exposure to 20-mM caffeine for 24 hours magnified reduced cell viability and enhanced apoptotic cell death induced by 200 mM of ethanol pretreatment. The phosphorylation of mTOR, p70S6K, and 4E-BP1 markedly decreased in cells exposed to caffeine after ethanol pretreatment, associated with a decrease of the mitochondrial membrane potential (ΔΨm). These findings suggested that caffeine treatment after neuronal cells were exposed to ethanol resulted in marked cell damages, mediated through enhanced inhibition of mTOR/p70S6K/4E-BP1 signaling leading to impaired ΔΨm and, eventually, apoptotic cell death.

The influence of caffeine on ethyl glucuronide levels in rat serum and in rat hair

BACKGROUND

Ethanol and caffeine are the most widely used psychoactive substances in the world, with an observed steady increase in the combined consumption of alcohol and caffeine. Specific signs of ethanol-caffeine interactions have been reported both in humans and in animals. The metabolic effects of these interactions have not been fully elucidated. There are no published reports on the influence of caffeine on ethyl glucuronide (EtG) formation. EtG is a direct metabolite of ethanol and is very often used as a biomarker of alcohol consumption. Here, we investigated the influence of caffeine on the formation of EtG in rat plasma and EtG incorporation into the hair.

METHODS

Studies were conducted on three male Wistar rat groups, each receiving either ethanol at 3 g/kg/day, ethanol (at the same dose) with caffeine at 3 mg/kg/day, or caffeine at 3 mg/kg/day for four weeks. EtG and caffeine levels were evaluated in hair and in blood after the last administration.

RESULTS

Blood EtG levels after the administration of ethanol together with caffeine were significantly higher than after the administration of ethanol alone. EtG levels in rat hair in the ethanol-and-caffeine group were also higher than in the ethanol-only group, but the difference was not statistically significant.

CONCLUSION

This study shows the possible effect of ethanol and caffeine co-administration on EtG formation. Caffeine stimulates EtG synthesis resulting in increased blood and, possibly, hair levels of this metabolite. However, the role of these changes in estimating alcohol consumption requires further studies.

Alcohol mixed with energy drink (AMED): A critical review and meta-analysis

The purpose of this systematic review and meta-analysis was to critically review the (1) prevalence of alcohol mixed with energy drink (AMED) consumption, (2) motives for AMED consumption, (3) correlates of AMED consumption, and (4) whether AMED consumption has an impact on (a) alcohol consumption, (b) subjective intoxication, and (c) risk-taking behavior. Overall a minority of the population consumes AMED, typically infrequently. Motives for AMED consumption are predominantly hedonistic and social. Meta-analyses revealed that AMED consumers drink significantly more alcohol than alcohol-only (AO) consumers. Within-subject comparisons restricted to AMED consumers revealed that alcohol consumption does not significantly differ between typical AMED and AO occasions. On past month heaviest drinking occasions, AMED users consume significantly less alcohol on AMED occasions when compared to AO occasions. AMED consumers experience significantly fewer negative consequences and risk-taking behavior on AMED occasions compared with AO occasions. Meta-analyses of subjective intoxication studies suggest that AMED consumption does not differentially affect subjective intoxication when compared to AO consumption. In conclusion, when compared to AO consumption, mixing alcohol with energy drink does not affect subjective intoxication and seems unlikely to increase total alcohol consumption, associated risk-taking behavior, nor other negative alcohol-related consequences. Further research may be necessary to fully reveal the effects of AMED.

The Safety of Ingested Caffeine: A Comprehensive Review

Caffeine is the most widely consumed psychoactive drug in the world. Natural sources of caffeine include coffee, tea, and chocolate. Synthetic caffeine is also added to products to promote arousal, alertness, energy, and elevated mood. Over the past decade, the introduction of new caffeine-containing food products, as well as changes in consumption patterns of the more traditional sources of caffeine, has increased scrutiny by health authorities and regulatory bodies about the overall consumption of caffeine and its potential cumulative effects on behavior and physiology. Of particular concern is the rate of caffeine intake among populations potentially vulnerable to the negative effects of caffeine consumption: pregnant and lactating women, children and adolescents, young adults, and people with underlying heart or other health conditions, such as mental illness. Here, we review the research into the safety and safe doses of ingested caffeine in healthy and in vulnerable populations. We report that, for healthy adults, caffeine consumption is relatively safe, but that for some vulnerable populations, caffeine consumption could be harmful, including impairments in cardiovascular function, sleep, and substance use. We also identified several gaps in the literature on which we based recommendations for the future of caffeine research.