After the medication period, participants who were eligible for the MRI session were selected at random, given an additional three days of medication, and scanned within those three days. To our knowledge, no studies to date have tested the effects of varenicline and naltrexone on structural MRI measures; however, to ensure that there were no significant gray matter differences between the medication groups, we conducted a whole-brain one-way between-subjects ANOVA . A total of 40 subjects participated in the neuroimaging study. The Institutional Review Board of University of California, Los Angeles, approved all procedures for the study. Participants were administered the Alcohol Dependence Scale , the FTND, and the 30-day Timeline Follow-back . The ADS is a 25-item self-report measure that identifies elements of alcohol dependence severity over the past 12 months, such as withdrawal symptoms and impaired control over alcohol use on a scored scale with a range of zero to 47. The FTND is a six-item self-report measure that captures features of nicotine dependence severity on a scored scale of zero to 10, and questions on this measure are not confined to a specific time frame of substance use. The TLFB assessed the daily amount of alcoholic drinks and cigarettes participants consumed in the past 30 days before the scan, from which mean drinks/drinking day and cigarettes/day were calculated. Previous research has indicated that gray matter tissue can regenerate within 14 days of alcohol abstinence in alcohol dependent patients and that gray matter regeneration is most profound within the first week to month of abstinence . Given these findings, we examined whether days to last drinking day before the imaging session correlated with gray matter density at the whole-brain level. Days to last drinking day was computed for each participant based on the TLFB information collected at the time of image acquisition. The analysis conducted included days to last drinking day as a predictor variable and age, gender, ICV, and ADS scores as covariates of interest.

Furthermore,indoor grow shelves to understand whether any of the effects were related to cannabis use within the current sample, we examined the relationship between frequency of cannabis use and drinking and nicotine variables using nonparametric Spearman’s correlations. Cannabis use was assessed using a single-item categorical question asking, “On average, how often do you smoke marijuana?”The purpose of the present study was to examine the relationship between quantity of alcohol/nicotine use and alcohol/nicotine dependence severity with gray matter density in heavy drinking smokers. Previous studies have focused primarily on alcohol users but have not excluded participants for nicotine use . Similarly, some prior studies that examined nicotine users did not establish exclusionary criteria based on alcohol use . These studies make it difficult to ascertain whether alcohol or nicotine use/dependence account for previous findings, as their individual contributions to gray matter structure or brain activity were not examined. Thus, it is critical to investigate the unique contributions of alcohol and nicotine use to brain morphometry in heavy drinking smokers. We hypothesized that there would be gray matter reductions in areas such as the ACC, dorsal striatum, and insula. Multiple regression analyses revealed that ADS scores significantly predicted gray matter density in the hypothalamus and right superior frontal gyrus and thus, the results differed from our initial hypotheses. Contrary to our expectations, there were no significant relationships with respect to quantity of alcohol use or nicotine dependence and quantity of cigarette use variables. The hypothalamus is part of the hypothalamic-pituitary-adrenal axis, which has been consistently shown to be dysregulated in individuals with AUD . HPA-axis dysregulation in alcohol-dependent individuals is marked by elevated blood glucocorticoid levels , which is associated with impairments in various brain regions, such as the prefrontal cortex, hippocampus, and the mesolimbic reward pathway . Impairments in these regions can lead to utilization of habit-based forms of learning or memory over goaldirected forms and profound cognitive memory impairments .

The current findings indicating ADS was negatively related to hypothalamic volume in heavy drinking smokers may suggest alterations in hypothalamic gray matter density that could be associated with changes in HPA-axis functioning and related cognitive impairments. Studies that integrate measures of gray matter density, cognitive functioning and markers of HPA-axis functioning in heavy drinking smokers are needed to clarify these associations. Moreover, several studies have linked hypothalamic gray matter degradation to the presence of Korsakoff Syndrome . These findings suggest that the development of Korsakoff Syndrome may exist on a spectrum, with hypothalamic gray matter atrophy acting as a relevant biomarker. Thus, our findings support the notion that alcohol dependence severity is related to gray matter degradation observed in the progression of uncomplicated alcoholism to Korsakoff syndrome. However, in a recent study of almost 3,000 Dutch nationals, it was demonstrated that alcohol use was associated with dysregulation in the HPA-axis system while alcohol dependence status was not . Given these contrasting findings from our study, it is necessary to further explore the respective contributions of alcohol use and dependence to the dysregulation of the HPA-axis system. The finding that higher ADS scores were negatively related to gray matter density in the superior frontal gyrus is supported by numerous previous studies indicating lower frontal gray matter density in alcohol users . In a review paper discussing the construct of impulsivity, areas of the PFC, such as the ventromedial and dorsolateral PFC, were posited to be involved in the neural circuitry of delay-related decision making and inhibitory control . Broadly speaking, it is possible that gray matter degradation in the frontal cortex is related to behavioral inhibition and decision making deficits in alcohol dependence , but further research is needed to shed light on how specific features of impulsivity relate to the gray matter atrophy observed in AUD.not excluded participants for nicotine use . Similarly, some prior studies that examined nicotine users did not establish exclusionary criteria based on alcohol use . These studies make it difficult to ascertain whether alcohol or nicotine use/dependence account for previous findings, as their individual contributions to gray matter structure or brain activity were not examined. Thus, it is critical to investigate the unique contributions of alcohol and nicotine use to brain morphometry in heavy drinking smokers.

We hypothesized that there would be gray matter reductions in areas such as the ACC, dorsal striatum, and insula. Multiple regression analyses revealed that ADS scores significantly predicted gray matter density in the hypothalamus and right superior frontal gyrus and thus, the results differed from our initial hypotheses. Contrary to our expectations, there were no significant relationships with respect to quantity of alcohol use or nicotine dependence and quantity of cigarette use variables. The hypothalamus is part of the hypothalamic-pituitary-adrenal axis, which has been consistently shown to be dysregulated in individuals with AUD . HPA-axis dysregulation in alcohol-dependent individuals is marked by elevated blood glucocorticoid levels , which is associated with impairments in various brain regions, such as the prefrontal cortex, hippocampus, and the mesolimbic reward pathway . Impairments in these regions can lead to utilization of habit-based forms of learning or memory over goaldirected forms and profound cognitive memory impairments . The current findings indicating ADS was negatively related to hypothalamic volume in heavy drinking smokers may suggest alterations in hypothalamic gray matter density that could be associated with changes in HPA-axis functioning and related cognitive impairments. Studies that integrate measures of gray matter density,planting growing rack cognitive functioning and markers of HPA-axis functioning in heavy drinking smokers are needed to clarify these associations. Moreover, several studies have linked hypothalamic gray matter degradation to the presence of Korsakoff Syndrome . These findings suggest that the development of Korsakoff Syndrome may exist on a spectrum, with hypothalamic gray matter atrophy acting as a relevant biomarker. Thus, our findings support the notion that alcohol dependence severity is related to gray matter degradation observed in the progression of uncomplicated alcoholism to Korsakoff syndrome. However, in a recent study of almost 3,000 Dutch nationals, it was demonstrated that alcohol use was associated with dysregulation in the HPA-axis system while alcohol dependence status was not . Given these contrasting findings from our study, it is necessary to further explore the respective contributions of alcohol use and dependence to the dysregulation of the HPA-axis system. The finding that higher ADS scores were negatively related to gray matter density in the superior frontal gyrus is supported by numerous previous studies indicating lower frontal gray matter density in alcohol users . In a review paper discussing the construct of impulsivity, areas of the PFC, such as the ventromedial and dorsolateral PFC, were posited to be involved in the neural circuitry of delay-related decision making and inhibitory control . Broadly speaking, it is possible that gray matter degradation in the frontal cortex is related to behavioral inhibition and decision making deficits in alcohol dependence , but further research is needed to shed light on how specific features of impulsivity relate to the gray matter atrophy observed in AUD.The FTND has fewer items than the ADS, so it is possible that lower variance of FTND scores made it difficult to detect relationships with gray matter density. It is also possible that nicotine dependence severity is not related to gray matter structure in the brain to the same extent as alcohol dependence severity. While several regions, such as the ACC, left dorsal striatum/insula, right dorsal striatum/insula, and the posterior cingulate cortex were identified as exhibiting gray matter atrophy in a meta-analysis of alcohol dependent individuals , a meta-analysis of chronic cigarette smokers only found the left ACC to show gray matter atrophy across several studies . The discrepancy may suggest differences between the two substances with respect to biological manifestations in the brain. However, previous studies found that smoking alcohol dependent individuals had significantly decreased cortical thickness in the insula and ACC when compared to nonsmoking alcohol dependent individuals .

Additionally, heavy drinking smokers were found to have significantly smaller temporal lobe and total gray matter volumes when compared to non-smoking heavy drinkers . Dissimilar to those studies, quantity of nicotine use or dependence severity were not found to significantly contribute to gray matter density in the current study. Given that Durazzo, Mon, Gazdzinski, and Meyerhoff included a sample with an average FTND score of 5.4 and participants who smoked an average of 20 cigarettes per day, while the present sample had an average FTND score of 3.69 and participants smoked an average of 14.56 cigarettes per day, it is possible that differences in nicotine dependence severity and quantity of use between the current and previous studies explain the discrepant findings. Previous research has found significant gray matter reduction in recovering alcohol users immediately before undergoing detoxification . This effect is ameliorated in abstaining light drinkers and abstaining recovering alcoholics versus relapsing recovering alcoholics . These findings support the notion that gray matter degradation effects could be attributable to the length of time between the last day an individual consumed alcohol and when he/she was scanned. The significant positive correlation between days to last drinking day and gray matter density in the left postcentral gyrus is consistent with the hypothesis that alcohol may cause dehydration and thus, volumetric reductions in the brain that are, in turn, ameliorated with short-term cessation of alcohol use. However, given that days to last drinking day was not related to gray matter density in the regions related to alcohol dependence severity, it is unlikely that recent alcohol use affected the current results. While our findings demonstrate the unique contribution of alcohol dependence severity to gray matter density in heavy drinking smokers, there are various limitations that should be noted. First, there was no matched control group to the comorbid users in this study. Although the multiple regression approach permits the investigation of specific contributions of alcohol and nicotine dependence and quantity of use to gray matter density, a control group would help ascertain whether the regions identified as significantly relating to alcohol dependence severity also differ in gray matter density from healthy controls. Second, the dependence severity and quantity of use measures did not encompass the exact same time frame, which may have resulted in relationships detected for dependence severity and gray matter density, but not quantity of use and gray matter density.