Endocannabinoids and Stress-Related Neurospsychiatric Disorders: A Systematic Review and Meta-Analysis of Basal Concentrations and Response to Acute Psychosocial Stress

Background: Dysregulation of the endocannabinoid (eCB) system is implicated in various stress-related neuropsychiatric disorders (SRDs), including anxiety, depression, and post-traumatic stress disorder (PTSD). In this systematic review and meta-analysis, our objectives were to characterize circulating anandamide (AEA) and 2-arachidonoylglycerol (2-AG) concentrations at rest and in response to acute laboratory-based psychosocial stress in individuals with SRDs and without (controls). Our primary aims were to assess the effects of acute psychosocial stress on eCB concentrations in controls (Aim 1), compare baseline (prestress) eCB concentrations between individuals with SRDs and controls (Aim 2), and explore differential eCB responses to acute psychosocial stress in individuals with SRDs compared with controls (Aim 3). Methods: On June 8, 2023, a comprehensive review of the MEDLINE (PubMed) database was conducted to identify original articles meeting inclusion criteria. A total of 1072, 1341, and 400 articles were screened for inclusion in Aims 1, 2, and 3, respectively. Results: Aim 1, comprised of seven studies in controls, revealed that most studies reported stress-related increases in AEA (86%, with 43% reporting statistical significance) and 2-AG (83%, though none were statistically significant except for one study in saliva). However, meta-analyses did not support these patterns (p's>0.05). Aim 2, with 20 studies, revealed that most studies reported higher baseline concentrations of both AEA (63%, with 16% reporting statistical significance) and 2-AG (60%, with 10% reporting statistical significance) in individuals with SRDs compared with controls. Meta-analyses confirmed these findings (p's<0.05). Aim 3, which included three studies, had only one study that reported statistically different stress-related changes in 2-AG (but not AEA) between individuals with PTSD (decrease) and controls (increase), which was supported by the meta-analysis (p<0.001). Meta-analyses showed heterogeneity across studies and aims (I2=14-97%). Conclusion: Despite substantial heterogeneity in study characteristics, samples, and methodologies, consistent patterns emerged, including elevated baseline AEA and 2-AG in individuals with SRDs compared with controls, as well as smaller stress-related increases in 2-AG in individuals with SRDs compared with controls. To consider eCBs as reliable biomarkers and potential intervention targets for SRDs, standardized research approaches are needed to clarify the complex relationships between eCBs, SRDs, and psychosocial stress.

Genetic variation in endocannabinoid signaling: Anxiety, depression, and threat- and reward-related brain functioning during the transition into adolescence

BACKGROUND

The endocannabinoid system modulates neural activity throughout the lifespan. In adults, neuroimaging studies link a common genetic variant in fatty acid amide hydrolase (FAAH C385A)-an enzyme that regulates endocannabinoid signaling-to reduced risk of anxiety and depression, and altered threat- and reward-related neural activity. However, limited research has investigated these associations during the transition into adolescence, a period of substantial neurodevelopment and increased psychopathology risk.

METHODS

This study included FAAH genotype and longitudinal neuroimaging and neurobehavioral data from 4811 youth (46% female; 9-11 years at Baseline, 11-13 years at Year 2) from the Adolescent Brain Cognitive DevelopmentSM Study. Linear mixed models examined the effects of FAAH and the FAAH x time interaction on anxiety and depressive symptoms, amygdala reactivity to threatening faces, and nucleus accumbens (NAcc) response to happy faces during the emotional n-back task.

RESULTS

A significant main effect of FAAH on depressive symptoms was observed, such that depressive symptoms were lower across both timepoints in those with the AA genotype compared to both AC and CC genotypes (p's<0.05). There were no significant FAAH x time interactions for anxiety, depression, or neural responses (p's>0.05). Additionally, there were no main effects of FAAH on anxiety or neural responses (p's>0.05).

CONCLUSIONS

Our findings add to emerging evidence linking the FAAH C385A variant to lower risk of psychopathology, and extend these findings to a developmental sample. In particular, we found lower depressive symptoms in FAAH AA genotypes compared to AC and CC genotypes. Future research is needed to characterize the role of the FAAH variant and the eCB system more broadly in neurodevelopment and psychiatric risk.

Smaller Hippocampal Volume Is Associated With Reduced Posttraumatic Stress Symptoms in Children With Cancer and Survivors Following a Brief Novel Martial Arts-Based Intervention

PURPOSE

Children with cancer and survivors frequently report posttraumatic stress symptoms (PTSS), which are associated with volumetric changes in stress-sensitive brain regions, including the hippocampus.

METHODS

We examined the impact of a novel, 4-week martial-arts-based meditative intervention on cancer-related PTSS in 18 pediatric patients and survivors and whether baseline hippocampal volumes correlate with PTSS severity and/or PTSS changes over time.

RESULTS

Overall, PTSS did not significantly change from baseline to post-intervention. Smaller hippocampal volume was correlated with more severe re-experiencing PTSS at baseline, and greater reductions in PTSS post-intervention.

CONCLUSIONS

Together, hippocampal volume may be a biomarker of PTSS severity and intervention response. Identifying hippocampal volume as a potential biomarker for PTSS severity and intervention response may allow for more informed psychosocial treatments.

Attention, attention! Posttraumatic stress disorder is associated with altered attention-related brain function

Posttraumatic stress disorder (PTSD) is a debilitating condition characterized by altered arousal, mood, and cognition. Studies report attentional alterations such as threat bias in individuals with PTSD, though this work has largely been conducted within emotionally-charged contexts (e.g., threatening stimuli). Emerging behavioral evidence suggests that PTSD-related attention deficits exist even in the absence of threatening cues or anxiety triggers. However, the role and functioning of attention brain circuits as they relate to PTSD remains underexplored. In this mini review, we highlight recent work using non-emotional stimuli to investigate the neurobiology of attention and disruptions to attention-related brain function among individuals with PTSD. We then discuss gaps in the current literature, including questions pertaining to the neural circuitry of attentional alterations in PTSD, as well as the contributions that trauma exposure, PTSD symptoms, comorbidities, and pre-existing vulnerabilities may have in this relationship. Finally, we suggest future directions for this emerging area of research, which may further inform knowledge surrounding the neurobiological underpinnings of PTSD and potential treatments.

Can digital health apps provide patients with support to promote structured diabetes education and ongoing self-management? A real-world evaluation of myDiabetes usage

Objective

Structured diabetes education has evidenced benefits yet reported uptake rates for those referred to traditional in-person programmes within 12 months of diagnosis were suboptimal. Digital health interventions provide a potential solution to improve diabetes education delivery at population scale, overcoming barriers identified with traditional approaches. myDiabetes is a cloud-based interactive digital health self-management app. This evaluation analysed usage data for people with type 2 diabetes focusing on digital structured diabetes education.

Methods

Descriptive quantitative analyses were conducted on existing anonymised user data over 12 months (November 2019-2020) to evaluate whether digital health can provide additional support to deliver diabetes education. Data was divided into two equal 6-month periods. As this overlapped the onset of COVID-19, analyses of its effect on usage were included as a secondary outcome. All data was reported via myDiabetes. Users were prescribed myDiabetes by National Health Service healthcare primary care teams. Those who registered for app use within the study period (n = 2783) were assessed for eligibility (n = 2512) and included if activated.

Results

Within the study period, n = 1245/2512 (49.6%) registered users activated myDiabetes. No statistically significant differences were observed between gender (p = 0.721), or age (p = 0.072) for those who activated (59.2 years, SD 12.93) and those who did not activate myDiabetes (57.6 years, SD 13.77). Activated users (n = 1119/1245 (89.8%)) viewed 11,572 education videos. No statistically significant differences were observed in education video views across age groups (p = 0.384), gender (p = 0.400), diabetes treatment type (p = 0.839) or smoking status (p = 0.655). Comparison of usage pre-COVID-19 and post-COVID-19 showed statistically significant increases in app activity (p ≤0.001).

Conclusion

Digital health is rapidly evolving in its role of supporting patients to self-manage. Since COVID-19 the benefits of digital technology have become increasingly recognised. There is potential for increasing diabetes education rates by offering patients a digital option in combination with traditional service delivery which should be substantiated through future research.

Are the kids really alright? Impact of COVID-19 on mental health in a majority Black American sample of schoolchildren

Children from historically disadvantaged groups (racial minorities, lower socioeconomic status [SES]) may be particularly susceptible to mental health consequences during the COVID-19 pandemic. We examined the impact of the pandemic, including mental health symptoms and COVID-19-related fears and behaviors, in a sample of majority Black American (72%) children (n=64, ages 7-10, 24 female) from an urban area with high infection rates. Children completed a mental health screening form prior to the pandemic (October 2019) and at two time points during the pandemic (May, August 2020). We examined the impact of SES on mental health changes over time, COVID-19 fears and behaviors, and perceived impact of the pandemic. We also tested whether baseline mental health predicted the impact of COVID-19. Children's fears of illness increased over time, and these effects were independent of race and SES. However, lower SES children reported more fears about social distancing during the pandemic as compared to higher SES children. Lower SES children also reported more internalizing symptoms at baseline, which decreased in this group following stay-at-home orders. Results highlight the need to reduce the risk of persistent fear and mitigate the mental health consequences among vulnerable pediatric populations during and after the pandemic.

Alterations in fear extinction neural circuitry and fear-related behavior linked to trauma exposure in children

Exposure to childhood trauma is extremely common (>60 %) and is a leading risk factor for fear-based disorders, including anxiety and posttraumatic stress disorder. These disorders are characterized by deficits in fear extinction and dysfunction in underlying neural circuitry. Given the strong and pervasive link between childhood trauma and the development of psychopathology, fear extinction may be a key mechanism. The present study tests the impact of childhood trauma exposure on fear extinction and underlying neural circuitry. Children (N = 44, 45 % trauma-exposed; 6-11 yrs) completed a novel two-day virtual reality fear extinction experiment. On day one, participants underwent fear conditioning and extinction. Twenty-four hours later, participants completed a test of extinction recall during fMRI. Conditioned fear was measured throughout the experiment using skin conductance and fear-related behavior, and activation in fear-related brain regions was estimated during recall. There were no group differences in conditioned fear during fear conditioning or extinction learning. During extinction recall, however, trauma-exposed children kept more distance from both the previously extinguished and the safety cue, suggesting poor differentiation between threat and safety cues. Trauma-exposed youth also failed to approach the previously extinguished cue over the course of extinction recall. The effects on fear-related behavior during extinction recall were accompanied by higher activation to the previously extinguished cue in fear-relevant brain regions, including the dorsal anterior cingulate cortex and anterior insula, in trauma-exposed relative to control children. Alterations in fear-related brain regions and fear-related behavior may be a core mechanism through which childhood trauma confers heightened vulnerability to psychopathology.

Impact of maternal childhood trauma on child behavioral problems: The role of child frontal alpha asymmetry

Childhood trauma is associated with many long-term negative outcomes, and is not limited to the individual experiencing the trauma, but extends to subsequent generations. However, mechanisms underlying the association between maternal childhood trauma and child psychopathology are not well understood. Here, we targeted frontal alpha asymmetry (FAA) as a potential underlying factor of the relationship between maternal childhood trauma and child behavioral problems. Electroencephalography (EEG) was recorded from (N = 45) children (Mean age = 57.9 months, SD = 3.13) during an eyes-closed paradigm in order to evaluate FAA. Mothers reported on their childhood trauma experiences using the Childhood Trauma Questionnaire (CTQ), and on their child's behavior using the child behavior checklist (CBCL). We found that maternal childhood trauma significantly predicted child total, internalizing, and externalizing behavior at age 5 years. We also observed a role for FAA such that it acted as a moderator, but not mediator, for behavioral problems. We found that children with relative more right/less left frontal activity were more at risk to develop behavioral problems when their mother had been exposed to trauma in her childhood. These results indicate that child frontal asymmetry may serve as a susceptibility marker for child behavioral problems.

Nitrogen use efficiency and nitrous oxide emissions from five UK fertilised grasslands

Intensification of grasslands is necessary to meet the increasing demand of livestock products. The application of nitrogen (N) on grasslands affects the N balance therefore the nitrogen use efficiency (NUE). Emissions of nitrous oxide (N₂O) are produced due to N fertilisation and low NUE. These emissions depend on the type and rates of N applied. In this study we have compiled data from 5 UK N fertilised grassland sites (Crichton, Drayton, North Wyke, Hillsborough and Pwllpeiran) covering a range of soil types and climates. The experiments evaluated the effect of increasing rates of inorganic N fertiliser provided as ammonium nitrate (AN) or calcium ammonium nitrate (CAN). The following fertiliser strategies were also explored for a rate of 320 kg N ha^-1: using the nitrification inhibitor dicyandiamide (DCD), changing to urea as an N source and splitting fertiliser applications. We measured N₂O emissions for a full year in each experiment, as well as soil mineral N, climate data, pasture yield and N offtake. N₂O emissions were greater at Crichton and North Wyke whereas Drayton, Hillsborough and Pwllpeiran had the smallest emissions. The resulting average emission factor (EF) of 1.12% total N applied showed a range of values for all the sites between 0.6 and 2.08%. NUE depended on the site and for an application rate of 320 kg N ha^-1, N surplus was on average higher than 80 kg N ha^-1, which is proposed as a maximum by the EU Nitrogen Expert Panel. N₂O emissions tended to be lower when urea was applied instead of AN or CAN, and were particularly reduced when using urea with DCD. Finally, correlations between the factors studied showed that total N input was related to Nofftake and Nexcess; while cumulative emissions and EF were related to yield scaled emissions.

Age-related changes in brain hemodynamics; A calibrated MRI study

INTRODUCTION

Blood oxygenation-level dependent (BOLD) magnetic resonance imaging signal changes in response to stimuli have been used to evaluate age-related changes in neuronal activity. Contradictory results from these types of experiments have been attributed to differences in cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2 ). To clarify the effects of these physiological parameters, we investigated the effect of age on baseline CBF and CMRO2 .

MATERIALS AND METHODS

Twenty young (mean ± sd age, 28 ± 3 years), and 45 older subjects (66 ± 4 years) were investigated. A dual-echo pseudocontinuous arterial spin labeling (ASL) sequence was performed during normocapnic, hypercapnic, and hyperoxic breathing challenges. Whole brain and regional gray matter values of CBF, ASL cerebrovascular reactivity (CVR), BOLD CVR, oxygen extraction fraction (OEF), and CMRO2 were calculated.

RESULTS

Whole brain CBF was 49 ± 14 and 40 ± 9 ml/100 g/min in young and older subjects respectively (P < 0.05). Age-related differences in CBF decreased to the point of nonsignificance (B=-4.1, SE=3.8) when EtCO2 was added as a confounder. BOLD CVR was lower in the whole brain, in the frontal, in the temporal, and in the occipital of the older subjects (P<0.05). Whole brain OEF was 43 ± 8% in the young and 39 ± 6% in the older subjects (P = 0.066). Whole brain CMRO2 was 181 ± 60 and 133 ± 43 µmol/100 g/min in young and older subjects, respectively (P<0.01).

DISCUSSION

Age-related differences in CBF could potentially be explained by differences in EtCO2 . Regional CMRO2 was lower in older subjects. BOLD studies should take this into account when investigating age-related changes in neuronal activity.

Temporal B0 field variation effects on MRSI of the human prostate at 7 T and feasibility of correction using an internal field probe

Spectral degradations as a result of temporal field variations are observed in MRSI of the human prostate. Moving organs generate substantial temporal and spatial field fluctuations as a result of susceptibility mismatch with the surrounding tissue (i.e. periodic breathing, cardiac motion or random bowel motion). Nine patients with prostate cancer were scanned with an endorectal coil (ERC) on a 7-T MR scanner. Temporal B0 field variations were observed with fast dynamic B0 mapping in these patients. Simulations of dynamic B0 corrections were performed using zero- to second-order shim terms. In addition, the temporal B0 variations were applied to simulated MR spectra causing, on average, 15% underestimation of the choline/citrate ratio. Linewidth distortions and frequency shifts (up to 30 and 8 Hz, respectively) were observed. To demonstrate the concept of observing local field fluctuations in real time during MRSI data acquisition, a field probe (FP) tuned and matched for the (19)  F frequency was incorporated into the housing of the ERC. The data acquired with the FP were compared with the B0 field map data and used to correct the MRSI datasets retrospectively. The dynamic B0 mapping data showed variations of up to 30 Hz (0.1 ppm) over 72 s at 7 T. The simulated zero-order corrections, calculated as the root mean square, reduced the standard deviation (SD) of the dynamic variations by an average of 41%. When using second-order corrections, the reduction in the SD was, on average, 56%. The FP data showed the same variation range as the dynamic B0 data and the variation patterns corresponded. After retrospective correction, the MRSI data showed artifact reduction and improved spectral resolution. B0 variations can degrade the MRSI substantially. The simple incorporation of an FP into an ERC can improve prostate cancer MRSI without prior knowledge of the origin of the dynamic field distortions.

Assessing the probability of carbon and greenhouse gas benefit from the management of peat soils

This study proposes a method for assessing the probability that land management interventions will lead to an improvement in the carbon sink represented by peat soils. The method is able to: combine studies of different carbon uptake and release pathways in order to assess changes on the overall carbon or greenhouse gas budget; calculate the probability of the management or restoration leading to an improvement in the budget; calculate the uncertainty in that probability estimate; estimate the equivalent number of complete budgets available from the combination of the literature; test the difference in the outcome of different land management interventions; and provide a method for updating the predicted probabilities as new studies become available. Using this methodology, this study considered the impact of: afforestation, managed burning, drainage, drain-blocking, grazing removal; and revegetation, on the carbon budget of peat soils in the UK. The study showed that afforestation, drain-blocking, revegetation, grazing removal and cessation of managed burning would bring a carbon benefit, whereas deforestation, managed burning and drainage would bring a disbenefit. The predicted probabilities of a benefit are often equivocal as each management type or restoration often leads to increase in uptake in one pathway while increasing losses in another.

Effects of past sewage sludge additions on heavy metal availability in light textured soils: implications for crop yields and metal uptakes

The effect of heavy metal additions in past sewage sludge applications on soil metal availability and the growth and yield of crops was evaluated at two sites in the UK. At Gleadthorpe, sewage sludges enriched with salts of zinc (Zn), copper (Cu) and nickel (Ni) had been applied to a loamy sand in 1982 and additionally naturally contaminated Zn and Cu sludge cakes in 1986. At Rosemaund, sewage sludges naturally contaminated with Zn, Cu, Ni and chromium (Cr) had been applied in 1968-1971 to a sandy loam. From 1994 to 1997, the yields of both cereals and legumes at Gleadthorpe were up to 3 t/ha lower than the no-sludge control where total topsoil Zn and Cu concentrations exceeded 200 and 120 mg/kg, respectively, but only when topsoil ammonium nitrate extractable metal levels also exceeded 40 mg/kg Zn and 0.9 mg/kg Cu. At Rosemaund, yields were only decreased where total topsoil Cu concentrations exceeded 220 mg/kg or 0.7 mg/kg ammonium nitrate extractable Cu. These results demonstrate the importance of measuring extractable as well as total heavy metal concentrations in topsoils when assessing likely effects on plant yields and metal uptakes, and setting soil quality criteria.