CLOCK is suggested to associate with comorbid alcohol use and depressive disorders

Individual patterns of activity predict the response to physical exercise as an intervention in mild to moderate depression

Physical exercise (PE) as antidepressive intervention is a promising alternative, as shown by multiple meta-analyses. However, there is no consensus regarding optimal intensity and duration of exercise, and there are no objective criteria available for personalized indication of treatment. The aims of this study were (1) to evaluate whether individual activity patterns before intervention can predict the response to treatment; and (2) to evaluate whether the patient outcome can be improved by using prior information on treatment efficacy at individual level. The study included subjects with mild to moderate depression randomized to three PE regimens as antidepressive intervention. Features extracted from actigraphy recordings were used for training linear regression ensembles to predict the response to treatment. The Bayesian analysis of coefficients yielded distinct signatures in enriched feature subsets for each PE regimen. Next, we used a counterfactual approach by virtually assigning each patient to the PE regimen predicted to yield best outcome. This procedure significantly increased the remission rates as compared to random assignment to treatment. Our data suggest that the analysis of individual patterns of activity can identify a PE regimen to yield the best results, and that assignment to PE regimen using this information would significantly increase remission rate.

Sex- and Substance-Specific Associations of Circadian-Related Genes with Addiction in the UK Biobank Cohort Implicate Neuroplasticity Pathways

BACKGROUND/OBJECTIVES

The circadian clockwork is implicated in the etiology of addiction, with circadian rhythm disruptions bidirectionally linked to substance abuse, but the molecular mechanisms that underlie this connection are not well known.

METHODS

Here, we use machine learning to reveal sex- and substance-specific associations with addiction in variants from 51 circadian-related genes (156,702 SNPs) in 98,800 participants from a UK Biobank cohort. We further analyze SNP associations in a subset of the cohort for substance-specific addictions (alcohol, illicit drugs (narcotics), and prescription drugs (opioids)).

RESULTS

We find robust (OR > 10) and novel sex-specific and substance-specific associations with variants in synaptic transcription factors (ZBTB20, CHRNB3) and hormone receptors (RORA), particularly in individuals addicted to narcotics and opioids. Circadian-related gene variants associated with male and female addiction were non-overlapping; variants in males primarily involve dopaminergic pathways, while variants in females factor in metabolic and inflammation pathways, with a novel gene association of female addiction with DELEC1, a gene of unknown function.

CONCLUSIONS

Our findings underscore the complexity of genetic pathways associated with addiction, involving core clock genes and circadian-regulated pathways, and reveal novel circadian-related gene associations that will aid the development of targeted, sex-specific therapeutic interventions for substance abuse.

Circadian Typology and Physical Activity in Young Adults with Gaming Disorder

Background and Objectives: Exploring daily lifestyle characteristics in individuals with gaming disorder (GD) might identify underlying causes and intervention points. However, integrative and subjective assessments are lacking in studies on this topic. This study aimed to assess circadian typology and physical activity in young adults with GD. Materials and Methods: We recruited 60 participants with GD and 120 age- and sex-matched controls. GD and delayed sleep phase syndrome (DSPS) were diagnosed through structured interviews. Physical activity and sleep patterns were measured using actigraphy. Self-reported measures were chronotype and insomnia by using composite scale of morningness (CSM) and the Pittsburg insomnia rating scale (PIRS). Results: We found that DSPS and eveningness chronotype was more prevalent in the GD group than in the control group. The GD group also contained more participants with insomnia with higher PIRS and a longer time to fall asleep compared with the control group. The GD group had lower physical activity levels for daily calorie expenditure, daily steps, and daily walking distance compared with the control group. No significant differences were observed in body weight and sleep duration between these groups. Conclusions: Individuals with GD, compared to HC, exhibit an eveningness chronotype, poorer sleep quality, lower physical activity, and higher obesity risk, suggesting that lifestyle adjustments like increased exercise and earlier sleep might help modify habitual behaviors and potentially further provide a way to treat GD.

A Complex Relationship Among the Circadian Rhythm, Reward Circuit and Substance Use Disorder (SUD)

The human brain not only controls the various physiological functions but is also the prime regulator of circadian rhythms, rewards, and behaviors. Environmental factors, professional stress, and social disintegration are regarded as the initial causative factors of addiction behavior. Shift work, artificial light exposure at night, and chronic and acute jet lag influence circadian rhythm dysfunction. The result is impaired neurotransmitter release, dysfunction of neural circuits, endocrine disturbance, and metabolic disorder, leading to advancement in substance use disorder. There is a bidirectional relationship between chronodisruption and addiction behavior. Circadian rhythm dysfunction, neuroadaptation in the reward circuits, and alteration in clock gene expression in the mesolimbic areas influence substance use disorder (SUD), and chronotherapy has potential benefits in the treatment strategies. This review explores the relationship among the circadian rhythm dysfunction, reward circuit, and SUD. The impact of chronotherapy on SUD has also been discussed.

Disrupted Circadian Rhythms and Substance Use Disorders: A Narrative Review

Substance use disorder is a major global health concern, with a high prevalence among adolescents and young adults. The most common substances of abuse include alcohol, marijuana, cocaine, nicotine, and opiates. Evidence suggests that a mismatch between contemporary lifestyle and environmental demands leads to disrupted circadian rhythms that impair optimal physiological and behavioral function, which can increase the vulnerability to develop substance use disorder and related problems. The circadian system plays an important role in regulating the sleep-wake cycle and reward processing, both of which directly affect substance abuse. Distorted substance use can have a reciprocal effect on the circadian system by influencing circadian clock gene expression. Considering the detrimental health consequences and profound societal impact of substance use disorder, it is crucial to comprehend its complex association with circadian rhythms, which can pave the way for the generation of novel chronotherapeutic treatment approaches. In this narrative review, we have explored the potential contributions of disrupted circadian rhythms and sleep on use and relapse of different substances of abuse. The involvement of circadian clock genes with drug reward pathways is discussed, along with the potential research areas that can be explored to minimize disordered substance use by improving circadian hygiene.

Relative importance of intensity and spectrum of artificial light at night in disrupting behavior of a nocturnal rodent

The influence of light spectral properties on circadian rhythms is of substantial interest to laboratory-based investigation of the circadian system and to field-based understanding of the effects of artificial light at night. The trade-offs between intensity and spectrum regarding masking behaviors are largely unknown, even for well-studied organisms. We used a custom LED illumination system to document the response of wild-type house mice (Mus musculus) to 1-h nocturnal exposure of all combinations of four intensity levels (0.01, 0.5, 5 and 50 lx) and three correlated color temperatures (CCT; 1750, 1950 and 3000 K). Higher intensities of light (50 lx) suppressed cage activity substantially, and consistently more for the higher CCT light (91% for 3000 K, 53% for 1750 K). At the lowest intensity (0.01 lx), mean activity was increased, with the greatest increases for the lowest CCT (12.3% increase at 1750 K, 3% increase at 3000 K). Multiple linear regression confirmed the influence of both CCT and intensity on changes in activity, with the scaled effect size of intensity 3.6 times greater than that of CCT. Activity suppression was significantly lower for male than for female mice. Assessment of light-evoked cFos expression in the suprachiasmatic nucleus at 50 lx showed no significant difference between high and low CCT exposure. The significant differences by spectral composition illustrate a need to account for light spectrum in circadian studies of behavior, and confirm that spectral controls can mitigate some, but certainly not all, of the effects of light pollution on species in the wild.

Role of polygenic risk scores in the association between chronotype and health risk behaviors

BACKGROUND

This study explores the association between chronotypes and adolescent health risk behaviors (HRBs) by testing how genetic background moderates these associations and clarifies the influence of chronotypes and polygenic risk score (PRS) on adolescent HRBs.

METHODS

Using VOS-viewer software to select the corresponding data, this study used knowledge domain mapping to identify and develop the research direction with respect to adolescent risk factor type. Next, DNA samples from 264 students were collected for low-depth whole-genome sequencing. The sequencing detected HRB risk loci, 49 single nucleotide polymorphisms based to significant SNP. Subsequently, PRSs were assessed and divided into low, moderate, and high genetic risk according to the tertiles and chronotypes and interaction models were constructed to evaluate the association of interaction effect and clustering of adolescent HRBs. The chronotypes and the association between CLOCK-PRS and HRBs were examined to explore the association between chronotypes and mental health and circadian CLOCK-PRS and HRBs.

RESULTS

Four prominent areas were displayed by clustering information fields in network and density visualization modes in VOS-viewer. The total score of evening chronotypes correlated with high-level clustering of HRBs in adolescents, co-occurrence, and mental health, and the difference was statistically significant. After controlling covariates, the results remained consistent. Three-way interactions between chronotype, age, and mental health were observed, and the differences were statistically significant. CLOCK-PRS was constructed to identify genetic susceptibility to the clustering of HRBs. The interaction of evening chronotypes and high genetic risk CLOCK-PRS was positively correlated with high-level clustering of HRBs and HRB co-occurrence in adolescents, and the difference was statistically significant. The interaction between the sub-dimensions of evening chronotypes and the high genetic CLOCK-PRS risk correlated with the outcome of the clustering of HRBs and HRB co-occurrence.

CONCLUSIONS

The interaction of PRS and chronotype and the HRBs in adolescents appear to have an association, and the three-way interaction between the CLOCK-PRS, chronotype, and mental health plays important roles for HRBs in adolescents.

RETN gene polymorphisms interact with alcohol dependence in association with depression

BACKGROUND

Previous studies suggest that alcohol dependence is associated with increased risk of depression. The occurrence of depressive symptoms is related to polymorphisms in various genetic regions. This study aimed to investigate the interaction of RETN gene polymorphisms (rs1477341, rs3745368) with alcohol dependence on depressive symptoms in adult male during acute alcohol withdrawal.

METHODS

A total of 429 male adults were recruited in this study. Alcohol dependence was assessed using the Michigan alcoholism screening test (MAST). Depression was assessed using the 20-item self-rating depression scale (SDS). Hierarchical regression analysis was used to evaluate the interaction between genes and alcohol dependence on depression. Region of significance (ROS) test was used to explain the interaction effect. The strong and weak forms of the differential susceptibility and diathesis models were used to determine which fits the data better.

RESULTS

Our results showed that MAST scores were significantly positively associated with SDS scores (r = 0.23, p < 0.01) in alcohol-dependent patients during alcohol withdrawal. The interaction between genotype and alcohol dependence was significant (β = -0.14, p < 0.05) in a strong diathesis-stress model. Susceptibility for depression symptoms was associated with alcohol dependence in RETN rs1477341 A carriers. Specifically, those that showed more alcohol dependence and the A allele of RETN rs1477341 exhibited more depression symptoms. However, RETN rs3745368 had no significant interaction with alcohol dependence.

CONCLUSIONS

The A allele of RETN rs1477341 may correlate with susceptibility to depression symptoms in alcohol-dependent individuals during acute alcohol withdrawal.

Targeting the Maladaptive Effects of Binge Drinking on Circadian Gene Expression

Previous studies (1) support a role of circadian genes in regulating alcohol intake, and (2) reveal that harmful alcohol use alters circadian rhythms. However, there is minimal knowledge of the effects of chronic alcohol processes on rhythmic circadian gene expression across brain regions important for circadian biology and alcohol intake. Therefore, the present study sought to test the effects of chronic binge-like drinking on diurnal circadian gene expression patterns in the master circadian pacemaker (SCN), the ventral tegmental area (VTA), and the nucleus accumbens (NAc) in High Drinking in the Dark-1 (HDID-1) mice, a unique genetic risk model for drinking to intoxication. Consistent with earlier findings, we found that 8 weeks of binge-like drinking reduced the amplitude of several core circadian clock genes in the NAc and SCN, but not the VTA. To better inform the use of circadian-relevant pharmacotherapies in reducing harmful drinking and ameliorating alcohol's effects on circadian gene expression, we tested whether the casein kinase-1 inhibitor, PF-67046, or the phosphodiesterase type-4 (an upstream regulator of circadian signalling) inhibitor, apremilast, would reduce binge-like intake and mitigate circadian gene suppression. PF-67046 did not reduce intake but did have circadian gene effects. In contrast, apremilast reduced drinking, but had no effect on circadian expression patterns.

Altered expression of somatostatin signaling molecules and clock genes in the hippocampus of subjects with substance use disorder

Substance use disorders are a debilitating group of psychiatric disorders with a high degree of comorbidity with major depressive disorder. Sleep and circadian rhythm disturbances are commonly reported in people with substance use disorder and major depression and associated with increased risk of relapse. Hippocampal somatostatin signaling is involved in encoding and consolidation of contextual memories which contribute to relapse in substance use disorder. Somatostatin and clock genes also have been implicated in depression, suggesting that these molecules may represent key converging pathways involved in contextual memory processing in substance use and major depression. We used hippocampal tissue from a cohort of subjects with substance use disorder (n = 20), subjects with major depression (n = 20), subjects with comorbid substance use disorder and major depression (n = 24) and psychiatrically normal control subjects (n = 20) to test the hypothesis that expression of genes involved in somatostatin signaling and clock genes is altered in subjects with substance use disorder. We identified decreased expression of somatostatin in subjects with substance use disorder and in subjects with major depression. We also observed increased somatostatin receptor 2 expression in subjects with substance use disorder with alcohol in the blood at death and decreased expression in subjects with major depression. Expression of the clock genes Arntl, Nr1d1, Per2 and Cry2 was increased in subjects with substance use disorder. Arntl and Nr1d1 expression in comparison was decreased in subjects with major depression. We observed decreased expression of Gsk3β in subjects with substance use disorder. Subjects with comorbid substance use disorder and major depression displayed minimal changes across all outcome measures. Furthermore, we observed a significant increase in history of sleep disturbances in subjects with substance use disorder. Our findings represent the first evidence for altered somatostatin and clock gene expression in the hippocampus of subjects with substance use disorder and subjects with major depression. Altered expression of these molecules may impact memory consolidation and contribute to relapse risk.

Astrocyte Molecular Clock Function in the Nucleus Accumbens Is Important for Reward-Related Behavior

BACKGROUND

Substance use disorders are associated with disruptions in circadian rhythms. Both human and animal work have shown the integral role for circadian clocks in the modulation of reward behaviors. Astrocytes have emerged as key regulators of circadian rhythmicity. However, no studies to date have identified the role of circadian astrocyte function in the nucleus accumbens (NAc), a hub for reward regulation, or determined the importance of these rhythms for reward-related behavior.

METHODS

Using astrocyte-specific RNA sequencing across time of day, we first characterized diurnal variation of the NAc astrocyte transcriptome. We then investigated the functional significance of this circadian regulation through viral-mediated disruption of molecular clock function in NAc astrocytes, followed by assessment of reward-related behaviors, metabolic-related molecular assays, and whole-cell electrophysiology in the NAc.

RESULTS

Strikingly, approximately 43% of the astrocyte transcriptome has a diurnal rhythm, and key metabolic pathways were enriched among the top rhythmic genes. Moreover, mice with a viral-mediated loss of molecular clock function in NAc astrocytes show a significant increase in locomotor response to novelty, exploratory drive, operant food self-administration, and motivation. At the molecular level, these animals also show disrupted metabolic gene expression, along with significant downregulation of both lactate and glutathione levels in the NAc. Loss of NAc astrocyte clock function also significantly altered glutamatergic signaling onto neighboring medium spiny neurons, alongside upregulated glutamate-related gene expression.

CONCLUSIONS

Taken together, these findings demonstrate a novel role for astrocyte circadian molecular clock function in the regulation of the NAc and reward-related behaviors.

Patterns of activity correlate with symptom severity in major depressive disorder patients

Objective measures, such as activity monitoring, can potentially complement clinical assessment for psychiatric patients. Alterations in rest-activity patterns are commonly encountered in patients with major depressive disorder. The aim of this study was to investigate whether features of activity patterns correlate with severity of depression symptoms (evaluated by Montgomery-Åsberg Rating Scale (MADRS) for depression). We used actigraphy recordings collected during ongoing major depressive episodes from patients not undergoing any antidepressant treatment. The recordings were acquired from two independent studies using different actigraphy systems. Data was quality-controlled and pre-processed for feature extraction following uniform procedures. We trained multiple regression models to predict MADRS score from features of activity patterns using brute-force and semi-supervised machine learning algorithms. The models were filtered based on the precision and the accuracy of fitting on training dataset before undergoing external validation on an independent dataset. The features enriched in the models surviving external validation point to high depressive symptom severity being associated with less complex activity patterns and stronger coupling to external circadian entrainers. Our results bring proof-of-concept evidence that activity patterns correlate with severity of depressive symptoms and suggest that actigraphy recordings may be a useful tool for individual evaluation of patients with major depressive disorder.

Behavior change versus stability during the college-to-work transition: Life course and the "stickiness" of alcohol misuse at career entry

To what extent and under what conditions do college graduates disengage from employment-incompatible behaviors during the college-to-work transition? Drawing from the life course perspective, we proposed a model highlighting considerable stability of employment-incompatible behaviors during initial months of organizational socialization. Our model predicted that maturing out of such behaviors, which is expected by employers and beneficial to career adjustment, would be more likely to occur given a conducive transition context. Using a large dataset tracking graduates from their last semester in college to up to approximately 1.5 years after graduation and with alcohol use as our empirical referent, we demonstrated that a pattern of high-risk drinking behavior may remain even after the transition into full-time employment. We further showed that lower levels of perceived cohort drinking norms and higher levels of mentoring were associated with a higher probability of maturing out, manifesting in a transition from a high-risk drinking profile before graduation to a moderate drinking profile after starting full-time employment. Finally, we found that maturing out was associated with lagged outcomes including lower levels of sleep problems and depression and fewer work days lost to absenteeism, thus underscoring the consequential nature of behavior profile shifts during the college-to-work transition.

Rev-erbα Knockout Reduces Ethanol Consumption and Preference in Male and Female Mice

Alcohol use is a contributor in the premature deaths of approximately 3 million people annually. Among the risk factors for alcohol misuse is circadian rhythm disruption; however, this connection remains poorly understood. Inhibition of the circadian nuclear receptor REV-ERBα is known to disrupt molecular feedback loops integral to daily oscillations, and impact diurnal fluctuations in the expression of proteins required for reward-related neurotransmission. However, the role of REV-ERBα in alcohol and substance use-related phenotypes is unknown. Herein, we used a Rev-erbα knockout mouse line and ethanol two-bottle choice preference testing to show that disruption of Rev-erbα reduces ethanol preference in male and female mice. Rev-erbα null mice showed the lowest ethanol preference in a two-bottle choice test across all genotypes, whereas there were no ethanol preference differences between heterozygotes and wildtypes. In a separate experiment, alcohol-consuming wildtype C57Bl/6N mice were administered the REV-ERBα/β inhibitor SR8278 (25 mg/kg or 50 mg/kg) for 7 days and alcohol preference was evaluated daily. No differences in alcohol preference were observed between the treatment and vehicle groups. Our data provides evidence that genetic variation in REV-ERBα may contribute to differences in alcohol drinking.

Disrupted circadian expression of beta-arrestin 2 affects reward-related µ-opioid receptor function in alcohol dependence

There is increasing evidence for a daily rhythm of μ-opioid receptor (MOR) efficacy and the development of alcohol dependence. Previous studies show that beta-Arrestin 2 (bArr2) has an impact on alcohol intake, at least partially mediated via modulation of MOR signaling, which in turn mediates the alcohol rewarding effects. Considering the interplay of circadian rhythms on MOR and alcohol dependence, we aimed to investigate bArr2 in alcohol dependence at different time-points of the day/light cycle on the level of bArr2 mRNA (in situ hybridization), MOR availability (receptor autoradiography) and MOR signaling (Damgo-stimulated G-protein coupling) in the nucleus accumbens of alcohol-dependent and non-dependent Wistar rats. Using a microarray data set we found that bArr2, but not bArr1, shows a diurnal transcription pattern in the accumbens of naïve rats with higher expression levels during the active cycle. In three-week abstinent rats, bArr2 is upregulated in the accumbens at the beginning of the active cycle (ZT15), whereas no differences were found at the beginning of the inactive cycle (ZT3), compared to controls. This effect was accompanied with a specific downregulation of MOR binding in the active cycle. Additionally, we detect a higher receptor coupling during the inactive cycle compared to the active cycle in alcohol-dependent animals. Together, we report a daily rhythmicity for bArr2 expression linked to an inverse pattern of MOR, suggesting an involvement for bArr2 on circadian regulation of G-protein coupled receptors in alcohol dependence. The presented data may have implications for the development of novel bArr2-related treatment targets for alcoholism.

Indoor lighting design for healthier workplaces: natural and electric light assessment for suitable circadian stimulus

Light, especially daylight, plays a critical role in human health as the main timer for circadian rhythms. Indoor environments usually lack the correct exposure to daylight and are highly dependent on electric lighting, disrupting the circadian rhythm and compromising the health of occupants. The methodology proposed assesses the combination of natural and electric lighting on circadian rhythms for operational environments. The case study chosen examines a 24/7 laboratory area representing an open-plan shift-work area. Several electric lighting scenarios under different sky conditions have been assessed, considering a variable window size and resulting in a spectrum which establishes the indoor circadian regulation performance according to the amount of light perceived. A set of configurations is presented to determine optimal electric lighting configuration based on natural light conditions in order to ensure a suitable circadian stimulus and the electric lighting flux threshold for different scenarios, benefiting occupants' health while also ensuring energy conservation.

Every Night and Every Morn: Effect of Variation in CLOCK Gene on Depression Depends on Exposure to Early and Recent Stress

The role of circadian dysregulation is increasingly acknowledged in the background of depressive symptoms, and is also a promising treatment target. Similarly, stress shows a complex relationship with the circadian system. The CLOCK gene, encoding a key element in circadian regulation has been implicated in previous candidate variant studies in depression with contradictory findings, and only a few such studies considered the interacting effects of stress. We investigated the effect of CLOCK variation with a linkage-disequilibrium-based clumping method, in interaction with childhood adversities and recent negative life events, on two phenotypes of depression, lifetime depression and current depressive symptoms in a general population sample. Methods: Participants in NewMood study completed questionnaires assessing childhood adversities and recent negative life events, the Brief Symptom Inventory to assess current depressive symptoms, provided data on lifetime depression, and were genotyped for 1054 SNPs in the CLOCK gene, 370 of which survived quality control and were entered into linear and logistic regression models with current depressive symptoms and lifetime depression as the outcome variable, and childhood adversities or recent life events as interaction variables followed by a linkage disequilibrium-based clumping process to identify clumps of SNPs with a significant main or interaction effect. Results: No significant clumps with a main effect were found. In interaction with recent life events a significant clump containing 94 SNPs with top SNP rs6825994 for dominant and rs6850524 for additive models on current depression was identified, while in interaction with childhood adversities on current depressive symptoms, two clumps, both containing 9 SNPs were found with top SNPs rs6828454 and rs711533. Conclusion: Our findings suggest that CLOCK contributes to depressive symptoms, but via mediating the effects of early adversities and recent stressors. Given the increasing burden on circadian rhythmicity in the modern lifestyle and our expanding insight into the contribution of circadian disruption in depression especially as a possible mediator of stress, our results may pave the way for identifying those who would be at an increased risk for depressogenic effects of circadian dysregulation in association with stress as well as new molecular targets for intervention in stress-related psychopathologies in mood disorders.

Shiftwork, functional bowel symptoms, and the microbiome

BACKGROUND

There are about 15 million Americans working full-time on evening, night, or rotating shifts. Between 48% and 81.9% of those working rotating or night shifts report abdominal pain, constipation, diarrhea and other symptoms of functional bowel disorders. The basis for this high prevalence of functional bowel disorders, including irritable bowel syndrome (IBS), among shift workers is unknown. Animal studies, however, suggest that circadian disruption, similar to that in shift workers, may contribute to the development of GI complaints among shift workers by altering the composition and normal diurnal rhythmicity of the resident intestinal microbes. Therefore, the present study was designed to determine if there were differences in (1) composition and diversity of the microbiome of night shift workers compared to day shift workers; and (2) the composition and diversity of the microbiome among shift workers experiencing functional bowel symptoms compared to shift workers who did not experience functional bowel symptoms.

METHODS

Fifty-one full time staff nurses who worked either 12-hour day or night shifts completed demographic information, and the Rome III IBS module. They also collected two samples of gut microbiota before the beginning and at the end of their last work shift on day 14, using validated field-tested methods consistent with the Human Microbiome Project. After DNA extraction, 16S rRNA sequencing and assignment to the genus level was completed, samples were then compared to determine if there were (1) differences in the diversity and profile of the microbiome by shift type; (2) if there were differences in the microbiome by time of day for collection; and (3) whether there were differences in the diversity and profile of the microbiome of nurses with IBS and those without IBS.

RESULTS

There were no differences in alpha or beta diversity of gut microbiota when specimens from day and night shift nurses were compared. There were however marginal differences in beta diversity when specimens collected at the beginning and end of the shifts were compared, with seven OTUs being differentially abundant when collected from day shift workers in the evening. There were also three OTUs to be differentially abundant in participants reporting IBS symptoms.

Association between Alcohol Drinking Status and Depressive Symptoms in Korean Adults

We investigated the association between alcohol drinking status and depressive symptoms in a representative sample of South Korean adults using data from the 2017 Korea Community Health Survey (KCHS), which included 216,771 participants (99,845 men and 116,926 women). Depression was defined as a Patient Health Questionnaire-9 score of ≥10. Multivariate logistic regression using sampling weights was used to assess the relationship between alcohol drinking status and depression after adjusting for potential confounders. Alcohol intake was nonlinearly associated with depression; the risk of depression was the lowest in men who were moderate drinkers and women who were light drinkers. In men, heavy drinkers (odds ratio [OR] 1.41, 95% confidence interval [CI] 1.19–1.67), light drinkers (OR 1.13, 95% CI 0.94–1.36), infrequent drinkers (OR 1.31, 95% CI 1.00–1.73), and lifetime abstainers (OR 1.38, 95% CI 1.09–1.75) were at a higher risk of depression than moderate drinkers. In women, moderate drinkers (OR 1.19, 95% CI 1.02–1.40) and heavy drinkers (OR 1.56, 95% CI 1.33–1.84) were at a higher risk of depression than light drinkers; however, infrequent drinkers and lifetime abstainers were not at a high risk of depression. In both men and women, former drinkers were at a higher risk of depression (OR 1.61, 95% CI 1.34–1.93 and OR 1.25, 95% CI 1.09–1.43, respectively). In conclusion, the association between alcohol drinking status and depression was nonlinear in both sexes. Further investigation of age- and sex-specific factors related to the association between alcohol use and depression is needed.

Circadian rhythms and substance use disorders: A bidirectional relationship

The circadian system organizes circadian rhythms (biological cycles that occur around 24 h) that couple environmental cues (zeitgebers) with internal functions of the organism. The misalignment between circadian rhythms and external cues is known as chronodisruption and contributes to the development of mental, metabolic and other disorders, including cancer, cardiovascular diseases and addictive disorders. Drug addiction represents a global public health concern and affects the health and well-being of individuals, families and communities. In this manuscript, we reviewed evidence indicating a bidirectional relationship between the circadian system and the development of addictive disorders. We provide information on the interaction between the circadian system and drug addiction for each drug or drug class (alcohol, cannabis, hallucinogens, psychostimulants and opioids). We also describe evidence showing that drug use follows a circadian pattern, which changes with the progression of addiction. Furthermore, clock gene expression is also altered during the development of drug addiction in many brain areas related to drug reward, drug seeking and relapse. The regulation of the glutamatergic and dopaminergic neurocircuitry by clock genes is postulated to be the main circadian mechanism underlying the escalation of drug addiction. The bidirectional interaction between the circadian system and drug addiction seems to be mediated by the effects caused by each drug or class of drugs of abuse. These studies provide new insights on the development of successful strategies aimed at restoring/stabilizing circadian rhythms to reduce the risk for addiction development and relapse.

Rhythms, Reward, and Blues: Consequences of Circadian Photoperiod on Affective and Reward Circuit Function

Circadian disruptions, along with altered affective and reward states, are commonly associated with psychiatric disorders. In addition to genetics, the enduring influence of environmental factors in programming neural networks is of increased interest in assessing the underpinnings of mental health. The duration of daylight or photoperiod is known to impact both the serotonin and dopamine systems, which are implicated in mood and reward-based disorders. This review first examines the effects of circadian disruption and photoperiod in the serotonin system in both human and preclinical studies. We next highlight how brain regions crucial for the serotoninergic system (i.e., dorsal raphe nucleus; DRN), and dopaminergic (i.e., nucleus accumbens; NAc and ventral tegmental area; VTA) system are intertwined in overlapping circuitry, and play influential roles in the pathology of mood and reward-based disorders. We then focus on human and animal studies that demonstrate the impact of circadian factors on the dopaminergic system. Lastly, we discuss how environmental factors such as circadian photoperiod can impact the neural circuits that are responsible for regulating affective and reward states, offering novel insights into the biological mechanisms underlying the pathophysiology, systems, and therapeutic treatments necessary for mood and reward-based disorders.

Association analysis between chronic obstructive pulmonary disease and polymorphisms in circadian genes

Background

Circadian genes have been suggested to play an important role in lung pathology. However, it remains unknown whether polymorphisms of these genes are associated with chronic obstructive pulmonary disease (COPD). Here, we aimed to investigate the association of circadian genes polymorphisms with COPD in a case-control study of 477 COPD patient and 323 control Han Chinese persons.

Methods

Genotyping assays were carried out for nine single nucleotide polymorphisms (SNPs) from five circadian genes (PER3, CLOCK, RORB, BMAL1 and CRY2) that were previously identified in lung pathology. Age, sex, BMI and smoking status and comorbidities were recorded for all subjects.

Results

No significant association was found in all SNP sites in overall subjects and no significant difference was found in age, sex, smoking status stratification analysis.

Discussion

The findings of this investigation indicated the effect of circadian genes polymorphisms on COPD susceptibility may only be small and possibly dependent on the subject factors, such as age and sex.

Alcohol Induced Depression: Clinical, Biological and Genetic Features

Background: In clinical practice, there is the need to have clinical and biological markers to identify induced depression. The objective was to investigate clinical, biological and genetic differences between Primary Major Depression (Primary MD) and Alcohol Induced MD (AI-MD). Methods: Patients, of both genders, were recruited from psychiatric hospitalisation units. The PRISM instrument was used to establish the diagnoses. Data on socio-demographic/family history, clinical scales for depression, anxiety, personality and stressful life events were recorded. A blood test was performed analysing biochemical parameters and a Genome Wide Association Study (GWAS) to identify genetic markers associated with AI-MD. Results: A total of 80 patients were included (47 Primary MD and 33 AI-MD). The AI-MD group presented more medical comorbidities and less family history of depression. There were differences in traumatic life events, with higher scores in the AI-MD (14.21 ± 11.35 vs. 9.30 ± 7.38; p = 0.021). DSM-5 criteria were different between groups with higher prevalence of weight changes and less anhedonia, difficulties in concentration and suicidal thoughts in the AI-MD. None of the genetic variants reached significance beyond multiple testing thresholds; however, some suggestive variants were observed. Conclusions: This study has found clinical and biological features that may help physicians to identify AI-MD and improve its therapeutic approach.

The role of alcohol-induced blackouts in symptoms of depression among young adults

OBJECTIVE

Blackouts are associated with other alcohol-related consequences and depression among young adults, but the mechanisms underlying these associations are unclear. Using two separate samples, we tested the hypothesis that blackouts would be linked to symptoms of depression due in part to their association with other alcohol-related consequences.

METHOD

Young adults who use alcohol completed assessments at baseline in Sample 1 (N₁ = 381, 58% female) and baseline, 3 months, and 6 months in Sample 2 (N₂ = 603, 53 % female). Bootstrapped confidence intervals were used to examine the direct and indirect effects of blackouts on depressive symptoms, using cross-sectional mediation analysis in Sample 1 and a counterfactual approach with longitudinal data in Sample 2.

RESULTS

In both samples, alcohol-induced blackouts were associated with alcohol-related consequences, which in turn were associated with symptoms of depression. In Sample 1, blackouts had both direct and indirect (mediated) effects on depressive symptoms. In Sample 2, blackouts measured at baseline only had an indirect effect on depressive symptoms six months later through other alcohol-related consequences at three months.

CONCLUSIONS

Among heavy-drinking college students, the majority of whom reported minimal symptoms of depression, blackouts were associated with increases in other alcohol-related consequences, which in turn were associated with increases in symptoms of depression. These findings suggest that prevention and intervention efforts targeting blackouts may help reduce other alcohol-related consequences among young adults.

DAILY-A Personalized Circadian Zeitgeber Therapy as an Adjunctive Treatment for Alcohol Use Disorder Patients: Study Protocol for a Randomized Controlled Trial

Background: Hallmarks of alcohol use disorder (AUD) are disturbances of circadian rhythms and everyday structures. While circadian rhythms dictate the timing of daily recurring activities such as sleep, activity, and meals, conversely, these activities represent time cues, so called Zeitgebers, that the circadian system uses to synchronize with the environment. Here we present a study protocol for our newly developed therapy approach for AUD patients, in which we take advantage of this mutual influence and stabilize and strengthen their circadian system by creating strict daily schedules for daily Zeitgeber activities. Since every person has a circadian system with its own characteristics and is subject to social obligations, the daily plans are personalized for each test person. Our hypothesis is that a regular exposure to Zeitgebers stabilizes behavioral and physiological circadian rhythms and thereby reduces the risk of alcohol relapses and depressive symptoms and facilitates physical recovery in AUD patients during the 1st weeks of their addiction therapy. Methods/design: The study is a 6-weeks single site trial with a controlled, randomized, single-blinded, parallel-group design including patients with a diagnosis of AUD. The study runs parallel to the standard addiction therapy of the clinic. Patients are randomly assigned to either an intervention group (DAILY) or a sham control group (placebo treatment). Questionnaires and physiological assessments of both groups are conducted before and immediately after the intervention or control treatment. According to our hypothesis, the primary outcomes of this study are improvements of regularity, alcohol consumption, and relapse rate in AUD patients compared to AUD patients receiving control treatment. Secondary outcomes are reduced depressive symptoms and increased physical recovery. Discussion: This study is a randomized controlled trial to investigate the efficacy of a personalized circadian Zeitgeber therapy as an adjunctive treatment for alcohol use disorder patients. The overall goal of this and more extended future studies is the development of an adjunctive therapy for AUD patients that is uncomplicated in its use and easy to implement in the clinical and everyday routine. Trial registration: This study is registered at the German Clinical Trial Register with the trial number DRKS00019093 on November 28, 2019.

Alcohol consumption predicts incidence of depressive episodes across 10 years among older adults in 19 countries

Alcohol consumption is increasing in many countries, and excessive alcohol consumption is particularly increasing among older adults. Excessive alcohol consumption causes morbidity and mortality, especially among older adults, including an increased risk of depressive episodes. We review the mechanisms through which alcohol consumption may affect depression, and argue that the effects of alcohol consumption on depressive episodes among older adults are understudied. We harmonized data among older adults (≥50 years) on alcohol consumption, depressive episodes, and an array of risk factors across 10 years and 19 countries (N=57,276). Alcohol consumption was categorized as current or long-term abstainer, occasional, moderate and heavy drinking at an average of 2.3 follow-up time points. Depressive episodes were measured through the CES-D or EURO-D. Multi-level Cox proportional frailty models in which the random effect has a multiplicative relationship to hazard were estimated with controls for co-occurring medical conditions, health behaviors, and demographics. Long-term alcohol abstainers had a higher hazard of depressive episodes (HR=1.14, 95% C.I. 1.08-1.21), as did those reporting occasional (HR=1.16, 95% C.I. 1.10-1.21) and heavy drinking (HR=1.22, 95% C.I. 1.13-1.30), compared with moderate drinking. Hazard ratios were attenuated in frailty models; heavy drinking, however, remained robustly associated in a random-effects model with a frailty component (HR=1.16, 95% C.I. 1.11-1.21). Interactions were observed by gender and smoking status: long-term abstainers, women's, and smokers' (HR for interaction, 1.04, 95% C.I. 1.00-1.07) hazards of depressive episodes increased more than what would be expected based on their multiplicative effects, when compared to moderate drinking, non-smoking men. Excessive alcohol consumption among older adults is a concern not only for physical, but also for mental health. Physician efforts to screen older adults for excessive alcohol use is critical for mental health to remain strong in aging populations.

The costs of negative affect attributable to alcohol consumption in later life: A within-between random longitudinal econometric model using UK Biobank

Aims

Research demonstrates a negative relationship between alcohol use and affect, but the value of deprecation is unknown and thus cannot be included in estimates of the cost of alcohol to society. This paper aims to examine this relationship and develop econometric techniques to value the loss in affect attributable to alcohol consumption.

Methods

Cross-sectional (n = 129,437) and longitudinal (n = 11,352) analyses of alcohol consumers in UK Biobank data were undertaken, with depression and neuroticism as proxies of negative affect. The cross-sectional relationship between household income, negative affect and alcohol consumption were analysed using regression models, controlling for confounding variables, and using within-between random models that are robust to unobserved heterogeneity. The differential in household income required to offset alcohol’s detriment to affect was derived.

Results

A consistent relationship between depression and alcohol consumption (β = 0.001, z = 7.64) and neuroticism and alcohol consumption (β = 0.001, z = 9.24) was observed in cross-sectional analyses, replicated in within-between models (depression β = 0.001, z = 2.32; neuroticism β = 0.001, z = 2.33). Significant associations were found between household income and depression (cross sectional β = -0.157, z = -23.86, within-between β = -0.146, z = -9.51) and household income and neuroticism (cross sectional β = -0.166, z = -32.02, within-between β = -0.158, z = -7.44). The value of reducing alcohol consumption by one gram/day was pooled and estimated to be £209.06 (95% CI £171.84 to £246.27).

Conclusions

There was a robust relationship between alcohol consumption and negative affect. Econometric methods can value the intangible effects of alcohol use and may, therefore, facilitate the fiscal determination of benefit.

Clock genes polymorphisms in male bipolar patients with comorbid alcohol abuse

BACKGROUND

Psychiatric comorbidity affects 24-65% patients with bipolar disorder (BD), 45% of which have alcohol abuse/dependence (AAD). Despite the fact that BD has an equal incidence in both genders, AAD more often occurs in men. We hypothesized that the presence of BD and AAD, reported as a secondary diagnosis, may result from a common genetic background. However, specific genetic factors predispose to gender differences.

METHODS

Based on the relationship between circadian clock genes pathway and BD/AAD we decided to test the connection of four core clock genes with common genetic background of both diseases. We analyzed 436 patients with BD, among which 17% were diagnosed with AAD. The control group consisted of 417 healthy subjects. We analyzed 44 SNPs of the previously described core molecular clock genes: CLOCK, ARNTL, TIMELESS and PER3.

RESULT

We found association of ARNTL gene (rs11600996) and PER3 gene (rs228642) polymorphisms with an increased risk of BD/AAD in a group of male patients. We also found that two other polymorphisms of PER3 gene, rs228682 and rs2640909, were associated with both AAD and family history of affective disorders.

LIMITATIONS

Possible factors that could have influenced the results are: relatively small sample size, gender disproportion and unverifiable data form the patient interview.

CONCLUSIONS

Our study confirms the existence of a link between clock genes and increased risk of alcohol abuse/dependence in male patients and the accumulation of risk genes in patients with a positive family history.

Focal Epilepsy and the Clock Gene

Investigators from Children's National Medical Center, Wenzhou Medical University, Virginia Tech, University of Colorado, University of Virginia, Georgetown University, University of Maryland, and Brown University performed transcriptome analysis on human epileptogenic tissue and extended the investigation by creating and testing mouse lines with targeted genetic deletions of the Clock gene.

Impact of Sleep and Circadian Rhythms on Addiction Vulnerability in Adolescents

Sleep homeostasis and circadian function are important maintaining factors for optimal health and well-being. Conversely, sleep and circadian disruptions are implicated in a variety of adverse health outcomes, including substance use disorders. These risks are particularly salient during adolescence. Adolescents require 8 to 10 hours of sleep per night, although few consistently achieve these durations. A mismatch between developmental changes and social/environmental demands contributes to inadequate sleep. Homeostatic sleep drive takes longer to build, circadian rhythms naturally become delayed, and sensitivity to the phase-shifting effects of light increases, all of which lead to an evening preference (i.e., chronotype) during adolescence. In addition, school start times are often earlier in adolescence and the use of electronic devices at night increases, leading to disrupted sleep and circadian misalignment (i.e., social jet lag). Social factors (e.g., peer influence) and school demands further impact sleep and circadian rhythms. To cope with sleepiness, many teens regularly consume highly caffeinated energy drinks and other stimulants, creating further disruptions in sleep. Chronic sleep loss and circadian misalignment enhance developmental tendencies toward increased reward sensitivity and impulsivity, increasing the likelihood of engaging in risky behaviors and exacerbating the vulnerability to substance use and substance use disorders. We review the neurobiology of brain reward systems and the impact of sleep and circadian rhythms changes on addiction vulnerability in adolescence and suggest areas that warrant additional research.

Circadian Mechanisms in Alcohol Use Disorder and Tissue Injury

Heavy use of alcohol can lead to addictive behaviors and to eventual alcohol-related tissue damage. While increased consumption of alcohol has been attributed to various factors including level of alcohol exposure and environmental factors such as stress, data from behavioral scientists and physiological researchers are revealing roles for the circadian rhythm in mediating the development of behaviors associated with alcohol use disorder as well as the tissue damage that drives physiological disease. In this work, we compile recent work on the complex mutually influential relationship that exists between the core circadian rhythm and the pharmacodynamics of alcohol. As we do so, we highlight implications of the relationship between alcohol and common circadian mechanisms of effected organs on alcohol consumption, metabolism, toxicity, and pathology.

The role of CLOCK gene in psychiatric disorders: Evidence from human and animal research

The circadian clock system drives daily rhythms in physiology, metabolism, and behavior in mammals. Molecular mechanisms of this system consist of multiple clock genes, with Circadian Locomotor Output Cycles Kaput (CLOCK) as a core member that plays an important role in a wide range of behaviors. Alterations in the CLOCK gene are associated with common psychiatric disorders as well as with circadian disturbances comorbidities. This review addresses animal, molecular, and genetic studies evaluating the role of the CLOCK gene on many psychiatric conditions, namely autism spectrum disorder, schizophrenia, attention-deficit/hyperactivity disorder, major depressive disorder, bipolar disorder, anxiety disorder, and substance use disorder. Many animal experiments focusing on the effects of the Clock gene in behavior related to psychiatric conditions have shown consistent biological plausibility and promising findings. In humans, genetic and gene expression studies regarding disorder susceptibility, sleep disturbances related comorbidities, and response to pharmacological treatment, in general, are in agreement with animal studies. However, the number of controversial results is high. Literature suggests that the CLOCK gene exerts important influence on these conditions, and influences the susceptibility to phenotypes of psychiatric disorders.

Purinergic Signaling in Neuron-Astrocyte Interactions, Circadian Rhythms, and Alcohol Use Disorder

Alcohol use disorder (AUD) is a debilitating condition marked by cyclic patterns of craving, use, and withdrawal. These pathological behaviors are mediated by multiple neurotransmitter systems utilizing glutamate, GABA, dopamine, ATP, and adenosine. In particular, purines such as ATP and adenosine have been demonstrated to alter the phase and function of the circadian clock and are reciprocally regulated by the clock itself. Importantly, chronic ethanol intake has been demonstrated to disrupt the molecular circadian clock and is associated with altered circadian patterns of activity and sleep. Moreover, ethanol has been demonstrated to disrupt purinergic signaling, while dysfunction of the purinergic system has been implicated in conditions of drug abuse such as AUD. In this review, we summarize our current knowledge regarding circadian disruption by ethanol, focusing on the reciprocal relationship that exists between oscillatory neurotransmission and the molecular circadian clock. In particular, we offer detailed explanations and hypotheses regarding the concerted regulation of purinergic signaling and circadian oscillations by neurons and astrocytes, and review the diverse mechanisms by which purinergic dysfuction may contribute to circadian disruption or alcohol abuse. Finally, we describe the mechanisms by which ethanol may disrupt or hijack endogenous circadian rhythms to induce the maladaptive behavioral patterns associated with AUD.

Genetic Risk Variants Associated With Comorbid Alcohol Dependence and Major Depression

Importance

Alcohol dependence (AD) and major depression (MD) are leading causes of disability that often co-occur. Genetic epidemiologic data have shown that AD and MD share a common possible genetic cause. The molecular nature of this shared genetic basis is poorly understood.

Objectives

To detect genetic risk variants for comorbid AD and MD and to determine whether polygenic risk alleles are shared with neuropsychiatric traits or subcortical brain volumes.

Design, Setting, and Participants

This genome-wide association study analyzed criterion counts of comorbid AD and MD in African American and European American data sets collected as part of the Yale-Penn study of the genetics of drug and alcohol dependence from February 14, 1999, to January 13, 2015. After excluding participants never exposed to alcohol or with missing information for any diagnostic criterion, genome-wide association studies were performed on 2 samples (the Yale-Penn 1 and Yale-Penn 2 samples) totaling 4653 African American participants and 3169 European American participants (analyzed separately). Tests were performed to determine whether polygenic risk scores derived from potentially related traits in European American participants could be used to estimate comorbid AD and MD.

Main Outcomes and Measures

Comorbid criterion counts (ranging from 0 to 14) for AD (7 criteria) and MD (9 criteria, scaled to 7) as defined by the DSM-IV.

Results

Of the 7822 participants (3342 women and 4480 men; mean [SD] age, 40.1 [10.7] years), the median comorbid criterion count was 6.2 (interquartile range, 2.3-10.9). Under the linear regression model, rs139438618 at the semaphorin 3A (SEMA3A [OMIM 603961]) locus was significantly associated with AD and MD comorbidity in African American participants in the Yale-Penn 1 sample (β = 0.89; 95% CI, 0.57-1.20; P = 2.76 × 10-8). In the independent Yale-Penn 2 sample, the association was also significant (β = 0.83; 95% CI, 0.39-1.28; P = 2.06 × 10-4). Meta-analysis of the 2 samples yielded a more robust association (β = 0.87; 95% CI, 0.61-1.12; P = 2.41 × 10-11). There was no significant association identified in European American participants. Analyses of polygenic risk scores showed that individuals with a higher risk of neuroticism (β = 1.01; 95% CI, 0.50-1.52) or depressive symptoms (β = 0.87; 95% CI, 0.32-1.42) and a lower level of subjective well-being (β = -0.94; 95% CI, -1.46 to -0.42) and educational attainment (β = -1.00, 95% CI, -1.57 to -0.44) had a higher level of AD and MD comorbidity, while larger intracranial (β = 1.07; 95% CI, 0.50 to 1.64) and smaller putamen volumes (β = -1.16; 95% CI, -1.86 to -0.46) were associated with higher risks of AD and MD comorbidity.

Conclusions and Relevance

SEMA3A variation is significantly and replicably associated with comorbid AD and MD in African American participants. Analyses of polygenic risk scores identified pleiotropy with neuropsychiatric traits and brain volumes. Further studies are warranted to understand the biological and genetic mechanisms of this comorbidity, which could facilitate development of medications and other treatments for comorbid AD and MD.

Circadian Rhythms and Substance Abuse: Chronobiological Considerations for the Treatment of Addiction

Reward-related learning, including that associated with drugs of abuse, is largely mediated by the dopaminergic mesolimbic pathway. Mesolimbic neurophysiology and motivated behavior, in turn, are modulated by the circadian timing system which generates ∼24-h rhythms in cellular activity. Both drug taking and seeking and mesolimbic dopaminergic neurotransmission can vary widely over the day. Moreover, circadian clock genes are expressed in ventral tegmental area dopaminergic cells and in mesolimbic target regions where they can directly modulate reward-related neurophysiology and behavior. There also exists a reciprocal influence between drug taking and circadian timing as the administration of drugs of abuse can alter behavioral rhythms and circadian clock gene expression in mesocorticolimbic structures. These interactions suggest that manipulations of the circadian timing system may have some utility in the treatment of substance abuse disorders. Here, the literature on bidirectional interactions between the circadian timing system and drug taking is briefly reviewed, and potential chronotherapeutic considerations for the treatment of addiction are discussed.

Circadian gene variants and breast cancer

The endogenous and self-sustained circadian rhythm generated and maintained in suprachiasmatic nucleus and peripheral tissues can coordinate various molecular, biochemical and physiological processes in living organisms resulting in the adaptation to environmental cues, e.g. light. Multifactorial breast cancer etiology also involves circadian gene alterations, especially among individuals exposed to light at night. Indeed, shift work that causes circadian disruption has been classified by the International Agency for Research on Cancer as a probable human carcinogen, group 2A. Thus it seems extremely important to recognize specific susceptible gene variants among around 20 candidate circadian genes that may be linked with breast cancer etiology. The aim of this review was to evaluate recent data investigating a putative link between circadian gene polymorphisms and breast cancer risk. We summarize fifteen epidemiological studies, including five studies on shift work that have indicated BMAL1, BMAL2, CLOCK, NPAS2, CRY1, CRY2, PER1, PER3 and TIMELESS as a candidate breast cancer risk variants.

Exercise as treatment for alcohol use disorders: systematic review and meta-analysis

OBJECTIVES

To conduct a systematic review and meta-analysis investigating effects of exercise for people with alcohol use disorders (AUDs) across multiple health outcomes. We also investigated the prevalence and predictors of dropout from exercise studies in AUDs.

DESIGN

Systematic review and random effects meta-analysis with meta-regression analyses.

DATA SOURCES

3 major electronic databases were searched from inception until April 2016 for exercise intervention studies in adults with AUDs.

ELIGIBILITY CRITERIA

Studies of acute exercise in people with AUDs; and randomised and non-randomised trials examining effects of long-term (≥2 weeks) exercise.

RESULTS

21 studies and 1204 unique persons with AUDs (mean age 37.8 years, mean illness duration 4.4 years) were included. Exercise did not reduce daily alcohol consumption (standardised mean difference (SMD) =-0.886, p=0.24), or the Alcohol Use Disorders Identification Test (AUDIT) total scores (SMD=-0.378, p=0.18). For weekly consumption (n=3 studies), a statistically significant difference was observed favouring exercise (SMD=-0.656, p=0.04), but not after adjustment for publication bias (SMD=-0.16, 95% CI -0.88 to 0.55). Exercise significantly reduced depressive symptoms versus control (randomised controlled trials (RCTs) =4; SMD=-0.867, p=0.006, I²=63%) and improved physical fitness (VO₂) (RCTs=3; SMD=0.564, p=0.01, I²=46%). The pooled dropout rate was 40.3% (95% CI 23.3% to 60.1%) which was no different to control conditions (OR=0.73, p=0.52). Dropouts were higher among men (β=0.0622, p<0.0001, R²=0.82).

LIMITATIONS

It was not possible to investigate moderating effects of smoking.

CONCLUSIONS

Available evidence indicates exercise appears not to reduce alcohol consumption, but has significant improvements in other health outcomes, including depression and physical fitness. Additional long-term controlled studies of exercise for AUDs are required.

Animal models of bipolar mania: The past, present and future

Bipolar disorder (BD) is the sixth leading cause of disability in the world according to the World Health Organization and affects nearly six million (∼2.5% of the population) adults in the United State alone each year. BD is primarily characterized by mood cycling of depressive (e.g., helplessness, reduced energy and activity, and anhedonia) and manic (e.g., increased energy and hyperactivity, reduced need for sleep, impulsivity, reduced anxiety and depression), episodes. The following review describes several animal models of bipolar mania with a focus on more recent findings using genetically modified mice, including several with the potential of investigating the mechanisms underlying 'mood' cycling (or behavioral switching in rodents). We discuss whether each of these models satisfy criteria of validity (i.e., face, predictive, and construct), while highlighting their strengths and limitations. Animal models are helping to address critical questions related to pathophysiology of bipolar mania, in an effort to more clearly define necessary targets of first-line medications, lithium and valproic acid, and to discover novel mechanisms with the hope of developing more effective therapeutics. Future studies will leverage new technologies and strategies for integrating animal and human data to reveal important insights into the etiology, pathophysiology, and treatment of BD.

Effect of circadian rhythm disturbance on morphine preference and addiction in male rats: Involvement of period genes and dopamine D1 receptor

It is claimed that a correlation exists between disturbance of circadian rhythms by factors such as alteration of normal light-dark cycle and the development of addiction. However, the exact mechanisms involved in this relationship are not much understood. Here we have studied the effect of constant light on morphine voluntary consumption and withdrawal symptoms and also investigated the involvement of Per1, Per2 and dopamine D1 receptor in these processes. Male wistar rats were kept under standard (LD) or constant light (LL) conditions for one month. The plasma concentration of melatonin was evaluated by enzyme-linked immunosorbent assay (ELISA). Real-time PCR was used to determine the mRNA expression of Per1, Per2 and dopamine D1 receptor in the striatum and prefrontal cortex. Morphine preference (50mg/L) was evaluated in a two-bottle-choice paradigm for 10 weeks and withdrawal symptoms were recorded after administration of naloxone (3mg/kg). One month exposure to constant light resulted in a significant decrease of melatonin concentration in the LL group. In addition, mRNA levels of Per2 and dopamine D1 receptor were up-regulated in both the striatum and prefrontal cortex of the LL group. However, expression of Per1 gene was only up-regulated in the striatum of LL rats in comparison to LD animals. Furthermore, after one month exposure to constant light, morphine consumption and preference ratio and also severity of naloxone-induced withdrawal syndrome were significantly greater in LL animals. It is concluded that exposure to constant light by up-regulation of Per2 and dopamine D1 receptor in the striatum and prefrontal cortex and up-regulation of Per1 in the striatum and the possible involvement of melatonin makes animals vulnerable to morphine preference and addiction.

Glutamatergic and HPA-axis pathway genes in bipolar disorder comorbid with alcohol- and substance use disorders

Glutamatergic neurotransmission has been shown to be dysregulated in bipolar disorder (BD), alcohol use disorder (AUD) and substance use disorder (SUD). Similarly, disruption in the hypothalamic-pituitary-adrenal (HPA)-axis has also been observed in these conditions. BD is often comorbid with AUD and SUD. The effects of the glutamatergic and HPA systems have not been extensively examined in individuals with BD-AUD and BD-SUD comorbidity. The aim of this investigation was to determine whether variants in the glutamatergic pathway and HPA-axis are associated with BD-AUD and BD-SUD comorbidity. The research cohort consisted of 498 individuals with BD type I from the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD). A subset of the cohort had comorbid current AUD and current SUD. A total of 1935 SNPs from both the glutamatergic and HPA pathways were selected from the STEP-BD genome-wide dataset. To identify population stratification, IBS clustering was performed using the program Plink 1.07. Single SNP association and gene-based association testing were conducted using logistic regression. A pathway analysis of glutamatergic and HPA genes was performed, after imputation using IMPUTE2. No single SNP was associated with BD-AUD or BD-SUD comorbidity after correction for multiple testing. However, from the gene-based analysis, the gene PRKCI was significantly associated with BD-AUD. The pathway analysis provided overall negative findings, although several genes including GRIN2B showed high percentage of associated SNPs for BD-AUD. Even though the glutamatergic and HPA pathways may not be involved in BD-AUD and BD-SUD comorbidity, PRKCI deserves further investigation in BD-AUD.

Clock genes × stress × reward interactions in alcohol and substance use disorders

Adverse life events and highly stressful environments have deleterious consequences for mental health. Those environmental factors can potentiate alcohol and drug abuse in vulnerable individuals carrying specific genetic risk factors, hence producing the final risk for alcohol- and substance-use disorders development. The nature of these genes remains to be fully determined, but studies indicate their direct or indirect relation to the stress hypothalamo-pituitary-adrenal (HPA) axis and/or reward systems. Over the past decade, clock genes have been revealed to be key-players in influencing acute and chronic alcohol/drug effects. In parallel, the influence of chronic stress and stressful life events in promoting alcohol and substance use and abuse has been demonstrated. Furthermore, the reciprocal interaction of clock genes with various HPA-axis components, as well as the evidence for an implication of clock genes in stress-induced alcohol abuse, have led to the idea that clock genes, and Period genes in particular, may represent key genetic factors to consider when examining gene × environment interaction in the etiology of addiction. The aim of the present review is to summarize findings linking clock genes, stress, and alcohol and substance abuse, and to propose potential underlying neurobiological mechanisms.

Assessing ethanol's actions in the suprachiasmatic circadian clock using in vivo and in vitro approaches

Research over the past decade has demonstrated substantial interactions between the circadian system and the processes through which alcohol affects behavior and physiology. Here we summarize the results of our collaborative efforts focused on this intersection. Using a combination of in vivo and in vitro approaches, we have shown that ethanol affects many aspects of the mammalian circadian system, both acutely as well as after chronic administration. Conversely, we have shown circadian influences on ethanol consumption. Importantly, we are beginning to delve into the cellular mechanisms associated with these effects. We are also starting to form a picture of the neuroanatomical bases for many of these actions. Finally, we put our current findings into perspective by suggesting new avenues of inquiry for our future efforts.

Circadian clock genes: effects on dopamine, reward and addiction

Addiction is a widespread public health issue with social and economic ramifications. Substance abuse disorders are often accompanied by disruptions in circadian rhythms including sleep/wake cycles, which can exacerbate symptoms of addiction and dependence. Additionally, genetic disturbance of circadian molecular mechanisms can predispose some individuals to substance abuse disorders. In this review, we will discuss how circadian genes can regulate midbrain dopaminergic activity and subsequently, drug intake and reward. We will also suggest future directions for research on circadian genes and drugs of abuse.

Clock genes in human alcohol abuse and comorbid conditions

Alcohol-use disorders are often comorbid conditions with mood and anxiety disorders. Clinical studies have demonstrated that there are abnormalities in circadian rhythms and clocks in patients with alcohol-use disorders. Circadian clock gene variants are therefore a fruitful target of interest. Concerning alcohol use, the current findings give support, but are preliminary to, the associations of ARNTL (BMAL1) rs6486120 with alcohol consumption, ARNTL2 rs7958822 and ARNTL2 rs4964057 with alcohol abuse, and PER1 rs3027172 and PER2 rs56013859 with alcohol dependence. Furthermore, it is of interest that CLOCK rs2412646 and CLOCK rs11240 associate with alcohol-use disorders only if comorbid with depressive disorders. The mechanistic basis of these associations and the intracellular actions for the encoded proteins in question remain to be elucidated in order to have the first insight of the potential small-molecule options for treatment of alcohol-use disorders.

Suicidal behavior in the context of disrupted rhythmicity in bipolar disorder--data from an association study of suicide attempts with clock genes

Suicidal behavior exhibits both circadian and annual rhythms. We were seeking an association between selected candidate clock genes and suicidal behavior in bipolar patients. The study included 441 bipolar patients and 422 controls and we genotyped 41 SNPs of the CLOCK, ARNTL, TIMELESS, PER3 genes. The main positive findings built up associations between selected polymorphisms and.

Diurnal and circadian regulation of reward-related neurophysiology and behavior

Here, we review work over the past two decades that has indicated drug reward is modulated by the circadian system that generates daily (i.e., 24h) rhythms in physiology and behavior. Specifically, drug-self administration, psychomotor stimulant-induced conditioned place preference, and locomotor sensitization vary widely across the day in various species. These drug-related behavioral rhythms are associated with rhythmic neural activity and dopaminergic signaling in the mesocorticolimbic pathways, with a tendency toward increased activity during the species typical wake period. While the mechanisms responsible for such cellular rhythmicity remain to be fully identified, circadian clock genes are expressed in these brain areas and can function locally to modulate both dopaminergic neurotransmission and drug-associated behavior. In addition, neural and endocrine inputs to these brain areas contribute to cellular and reward-related behavioral rhythms, with the medial prefrontal cortex playing a pivotal role. Acute or chronic administration of drugs of abuse can also alter clock gene expression in reward-related brain regions. Emerging evidence suggests that drug craving in humans is under a diurnal regulation and that drug reward may be influenced by clock gene polymorphisms. These latter findings, in particular, indicate that the development of therapeutic strategies to modulate the circadian influence on drug reward may prove beneficial in the treatment of substance abuse disorders.