Sex, Drugs, and TBI: The Role of Sex in Substance Abuse Related to Traumatic Brain Injuries

Effects of Repetitive Mild Traumatic Brain Injury on Corticotropin-Releasing Factor Modulation of Lateral Habenula Excitability and Motivated Behavior

Mild traumatic brain injury (mTBI) is a significant health burden due to mTBI-related chronic debilitating cognitive and psychiatric morbidities. Recent evidence from our laboratory suggests a possible dysregulation within reward/motivational circuit function at the level of a subcortical structure, the lateral habenula (LHb), where we demonstrated a causal role for hyperactive LHb in mTBI-induced motivational deficits in self-care grooming behavior in young adult male mice when exposed to mTBI injury during late adolescence (at ~8 weeks old). Here we extended this observation by further characterizing neurobehavioral effects of this repetitive closed head injury model of mTBI in both young adult male and female mice on LHb excitability, corticotropin releasing factor (CRF) modulation of LHb activity, and behavioral responses of motivation to self-care behavior, and approach versus avoidance behavior in the presence of a social- or threat-related stimulus. We show that mTBI increases LHb spontaneous tonic activity in female mice similar to what we previously observed in male mice as well as promoting LHb neuronal hyperexcitability and hyperpolarization-induced LHb bursting in both male and female mice. Interestingly, mTBI only increases LHb intrinsic excitability in male mice coincident with higher levels of the hyperpolarization-activated cation currents (HCN/Ih) and reduces levels of the M-type potassium currents while potentiating M-currents without altering intrinsic excitability in LHb neurons of female mice. Since persistent dysregulation of brain CRF systems is suggested to contribute to chronic psychiatric morbidities and that LHb neurons are highly responsive to CRF, we then tested whether LHb CRF subsystem becomes engaged following mTBI. We found that in vitro inhibition of CRF receptor type 1 (CRFR1) within the LHb normalizes mTBI-induced enhancement of LHb tonic activity and hyperexcitability in both sexes, suggesting that an augmented intra-LHb CRF-CRFR1-mediated signaling contributes to the overall LHb hyperactivity following mTBI. Behaviorally, mTBI diminishes motivation for self-care grooming in female mice as in male mice. mTBI also alters defensive behaviors in the looming shadow task by shifting the innate defensive behaviors towards more passive action-locking rather than escape behaviors in response to an aerial threat in both male and female mice as well as prolonging the latency to escape responses in female mice. While, this model of mTBI reduces social preference in male mice, it induces higher social novelty seeking during the novel social encounters in both male and female mice. Overall, our study provides further translational validity for the use of this preclinical model of mTBI for investigation of mTBI-related reward circuit dysfunction and mood/motivation-related behavioral deficits in both sexes while uncovering a few sexually dimorphic neurobehavioral effects of this model that may differentially affect young males and females when exposed to this type of mTBI injury during late adolescence.

Patterns of Alcohol Use in Hispanic Individuals with TBI over the Ten Years Post-Injury: A Model Systems Study

The study's aim was to examine alcohol consumption patterns and predictors of consumption across time among Hispanics with traumatic brain injury (TBI) in the U.S. within ten years post-injury. This longitudinal cohort study included 1342 Hispanic individuals (77.6% males) from the multi-site, longitudinal TBI Model Systems (TBIMS) database. The main outcome measures were consumption information, demographic, and injury characteristics. Across the full sample, alcohol consumption variables generally demonstrated quadratic movement characterized by an initial increase followed by a plateau or slight decrease over the ten years post-injury. The predictors of higher consumption were being men, single, with a history of excessive alcohol use, with a nonviolent mechanism of injury, shorter duration of PTA, and higher levels of education. Participants had a greater number of 5+ drinks/episode occurrences in the past month if they were men and had had a greater number of 5+ drinks/episode occurrences in the month before injury. There was no differential change in alcohol consumption over time as a function of these predictors. This study identified a profile of at-risk Hispanics with TBI for increased alcohol consumption. These individuals should be identified and targeted for early evidence-based alcohol intervention after TBI when results might be most favorable.

Adolescent alcohol and cannabis use as risk factors for head trauma in the Northern Finland Birth Cohort study 1986

BACKGROUND

The aim of this study was to assess the associations between cannabis use and frequency of alcohol intoxication in adolescence with the risk of traumatic brain injury and craniofacial fractures in early adulthood. Hypothesis was that using alcohol and cannabis in adolescence could increase the risk for head traumas.

METHODS

Data from the Northern Finland Birth Cohort 1986 (n = 9432 individuals) were used to investigate the prospective association between the self-reported frequency of alcohol intoxication (n = 6472) and cannabis use (n = 6586) in mid-adolescence and register-based, head trauma diagnoses by ages 32-33 years. To test the robustness of these associations, the statistical models were adjusted for a range of other confounders such as illicit drug use, previous head trauma and self-reported mental health problems.

RESULTS

In multivariate analyses, cannabis use was statistically significantly associated with a greater risk of traumatic brain injury among females [hazard ratio (HR) 1.9, 95% confidence interval (CI) 1.1-3.2, P = 0.024). Frequent alcohol intoxication was a statistically significant independent risk factor for both traumatic brain injury (HR 2.6, 95% CI 1.7-3.9, P < 0.001) and craniofacial fractures (HR 2.7, 95% CI 1.6-4.8, P < 0.001) among males.

CONCLUSIONS

Cannabis use in adolescence appears to associate independently with elevated risk for traumatic brain injury among females, and frequent alcohol intoxication in adolescence seems to associate with elevated risk of both traumatic brain injury and craniofacial fractures among males.

Sex-Specific and Traumatic Brain Injury Effects on Dopamine Receptor Expression in the Hippocampus

Traumatic brain injury (TBI) is a major health concern. Each year, over 50 million individuals worldwide suffer from TBI, and this leads to a number of acute and chronic health issues. These include affective and cognitive impairment, as well as an increased risk of alcohol and drug use. The dopaminergic system, a key component of reward circuitry, has been linked to alcohol and other substance use disorders, and previous research indicates that TBI can induce plasticity within this system. Understanding how TBI modifies the dopaminergic system may offer insights into the heightened substance use and reward-seeking behavior following TBI. The hippocampus, a critical component of the reward circuit, is responsible for encoding and integrating the spatial and salient aspects of rewarding stimuli. This study explored TBI-related changes in neuronal D2 receptor expression within the hippocampus, examining the hypothesis that sex differences exist in both baseline hippocampal D2 receptor expression and its response to TBI. Utilizing D2-expressing tdTomato transgenic male and female mice, we implemented either a sham injury or the lateral fluid percussion injury (FPI) model of TBI and subsequently performed a region-specific quantification of D2 expression in the hippocampus. The results show that male mice exhibit higher baseline hippocampal D2 expression compared to female mice. Additionally, there was a significant interaction effect between sex and injury on the expression of D2 in the hippocampus, particularly in regions of the dentate gyrus. Furthermore, TBI led to significant reductions in hippocampal D2 expression in male mice, while female mice remained mostly unaffected. These results suggest that hippocampal D2 expression varies between male and female mice, with the female dopaminergic system demonstrating less susceptibility to TBI-induced plasticity.

Physical Health and Well-being: Updates and the Way Ahead

INTRODUCTION

The Women in Combat Summit 2021 "Forging the Future: How Women Enhance the Fighting Force" took place during February 9-11, 2021, via a virtual conference platform. The third and final day of the Summit regarded the physical health and well-being of military women and included the topics of urogenital health, nutrition and iron-deficiency anemia, unintended pregnancy and contraception, and traumatic brain injury.

MATERIALS AND METHODS

After presentations on the topics earlier, interested conference attendees were invited to participate in focus groups to discuss and review policy recommendations for physical health and well-being in military women. Discussions centered around the topics discussed during the presentations, and suggestions for future Women in Combat Summits were noted. Specifics of the methods of the Summit are presented elsewhere in this supplement.

RESULTS

We formulated research and policy recommendations for urogenital health, nutrition and iron-deficiency anemia, contraception and unintended pregnancy, and traumatic brain injury.

CONCLUSIONS

In order to continue to develop the future health of military women, health care providers, researchers, and policymakers should consider the recommendations made in this supplement as they continue to build on the state of the science and forge the future.

High Risk of Substance Use Disorder-Related Outcomes in Veterans Released from Correctional Facilities in Mid to Late Life

BACKGROUND

Veterans Affairs (VA) is likely to encounter a growing number of veterans returning to the community in mid to late life following incarceration (i.e., experiencing reentry). Yet, rates of negative health outcomes due to substance use disorders (SUDs) in this population are unknown.

OBJECTIVE

To determine risk of and risk factors for SUD-related emergency department visits and inpatient hospitalizations (ED/IPH) and overdose death among older reentry veterans compared with never-incarcerated veterans.

DESIGN

Retrospective cohort study using national VA and Medicare healthcare systems data.

PARTICIPANTS

Veterans age  ≥50, incarcerated for  ≤5 consecutive years, and released between October 1, 2010, and September 30, 2017 (N = 18,803), were propensity score-matched 1:5 with never-incarcerated veterans (N = 94,015) on demographic characteristics, reason for Medicare eligibility, and SUD history.

MAIN MEASURES

SUD-related ED/IPH (overall and substance-specific) were obtained from in-/outpatient VA health services and CMS data within the year following release date/index date (through September 30, 2018). Overdose death within 1 year was identified using the National Mortality Data Repository. Fine-Gray proportional hazards regression compared risk of SUD-related ED/IPH and overdose death between the two groups.

RESULTS

The number of SUD-related ED/IPHs and overdose deaths was 2470 (13.1%) and 72 (0.38%) in the reentry sample versus 4402 (4.7%) and 198 (0.21%) in the never-incarcerated sample, respectively. Mid-to-late-life reentry was associated with higher risk of any SUD-related ED/IPH (13,136.2 vs. 2252.8 per 100,000/year; adjusted hazard ratio [AHR] = 2.19; 95% confidence interval [CI] = 2.08, 2.30) and overdose death (382.9 vs. 210.6 per 100,000/year; AHR = 2.24, 95% CI = 1.63, 3.08).

CONCLUSIONS

Older reentry veterans have more than double the risk of experiencing SUD-related ED/IPH (overall and substance-specific) and overdose death, even after accounting for SUD history and other likely confounders. These findings highlight the vulnerability of this population. Improved knowledge regarding SUD-related negative health outcomes may help to tailor VA reentry programming.

Intimate partner violence, substance use, and health comorbidities among women: A narrative review

Exposure to intimate partner violence (IPV), including physical, sexual, and psychological violence, aggression, and/or stalking, impacts overall health and can have lasting mental and physical health consequences. Substance misuse is common among individuals exposed to IPV, and IPV-exposed women (IPV-EW) are at-risk for transitioning from substance misuse to substance use disorder (SUD) and demonstrate greater SUD symptom severity; this too can have lasting mental and physical health consequences. Moreover, brain injury is highly prevalent in IPV-EW and is also associated with risk of substance misuse and SUD. Substance misuse, mental health diagnoses, and brain injury, which are highly comorbid, can increase risk of revictimization. Determining the interaction between these factors on the health outcomes and quality of life of IPV-EW remains a critical need. This narrative review uses a multidisciplinary perspective to foster further discussion and research in this area by examining how substance use patterns can cloud identification of and treatment for brain injury and IPV. We draw on past research and the knowledge of our multidisciplinary team of researchers to provide recommendations to facilitate access to resources and treatment strategies and highlight intervention strategies capable of addressing the varied and complex needs of IPV-EW.

Ovarian Steroids Mediate Sex Differences in Alcohol Reward After Brain Injury in Mice

Intoxication is a leading risk factor for injury, and TBI increases the risk for later alcohol misuse, especially when the injury is sustained in childhood. Previously, we modeled this pattern in mice, wherein females injured at postnatal day 21 drank significantly more than uninjured females, while we did not see this effect in males. However, the biological underpinnings of this sex difference have remained elusive. In this study, we utilize this preclinical model and traditional endocrine manipulations to assess the effect of perinatal sex steroids on post-injury ethanol response. We found that perinatal androgen administration and adult ovariectomy prevented the development of conditioned place preference to ethanol in females, while there was not an effect of gonadectomy either developmental time point on the severity of axonal degeneration. Finally, although TBI increased the number of microglia in males, there was no corresponding effect of gonadectomy, which suggests that males exhibit prolonged neuroinflammation after brain injury irrespective of circulating sex steroids. Taken together, our results indicate a potential role for ovarian sex steroids in the development of greater alcohol preference after a juvenile TBI in female mice.

The role of the stress system in recovery after traumatic brain injury: A tribute to Bruce S. McEwen

Traumatic brain injury (TBI) represents a major public health concern. Although the majority of individuals that suffer mild-moderate TBI recover relatively quickly, a substantial subset of individuals experiences prolonged and debilitating symptoms. An exacerbated response to physiological and psychological stressors after TBI may mediate poor functional recovery. Individuals with TBI can suffer from poor stress tolerance, impairments in the ability to evaluate stressors, and poor initiation (and cessation) of neuroendocrine stress responses, all of which can exacerbate TBI-mediated dysfunction. Here, we pay tribute to the pioneering neuroendocrinologist Dr. Bruce McEwen by discussing the ways in which his work on stress physiology and allostatic loading impacts the TBI patient population both before and after their injuries. Specifically, we will discuss the modulatory role of hypothalamic-pituitary-adrenal axis responses immediately after TBI and later in recovery. We will also consider the impact of stressors and stress responses in promoting post-concussive syndrome and post-traumatic stress disorders, two common sequelae of TBI. Finally, we will explore the role of early life stressors, prior to brain injuries, as modulators of injury outcomes.

Sports- and Physical Activity-Related Concussions, Binge Drinking and Marijuana Use among Adolescents: The Mediating Role of Depression and Suicidal Ideation

BACKGROUND

Although past studies have examined the adverse impact of sports- and physical activity-related concussions (SPACs) on health and mental health outcomes, there is a dearth of research investigating the association between SPACs and binge drinking and marijuana use.

OBJECTIVE

The objective of this study is to examine the cross-sectional association between SPACs and binge drinking and marijuana use among adolescents and whether symptoms of depression and suicidal ideation mediate this association.

METHODS

Data for this study came from the 2017 and 2019 National Youth Risk Behavior Survey. An analytic sample of 17,175 adolescents aged 14-18 years (50.2% male) was analyzed using binary logistic regression.

RESULTS

Of the 17,175 adolescents, 13.7% engaged in binge drinking and 19.3% used marijuana 30 days preceding the survey date. Approximately one in seven (14.1%) adolescents had SPACs during the past year. Upon controlling for the effects of other factors, adolescents who had SPACs had 1.74 times higher odds of engaging in binge drinking (AOR = 1.74, p<.001, 95% CI = 1.47-2.06) and 1.42 times higher odds of using marijuana (AOR = 1.42, p<.001, 95% CI = 1.24-1.62) than those who did not have SPACs. Symptoms of depression and suicidal ideation explained 12% of the association between SPACs and binge drinking, and 19% of the association between SPACs and marijuana use.

CONCLUSIONS

Understanding the association between SPACs and substance use and mental health could contribute to early identification of adolescents who may engage in substance use.