Impact of Childhood Trauma Exposure,Genetic Variation in Endocannabinoid Signaling,and Anxiety on Frontolimbic Pathways in Children

Abstract

Introduction:

The endocannabinoid (eCB) system plays a key role in modulating brain development, including myelination processes. Recent studies link a common variant (C385A, rs324420) in the fatty acid amide hydrolase (FAAH) gene to higher circulating eCB levels, lower anxiety, and altered frontolimbic development. Frontolimbic pathways, which demonstrate a protracted maturational course across childhood and adolescence, are associated with anxiety, and are vulnerable to environmental stressors such as trauma exposure. Here, we examined the impact of trauma exposure, FAAH genotype, and anxiety on frontolimbic white matter microstructure in children.

Materials and Methods:

We leveraged baseline data from the Adolescent Brain Cognitive Development (ABCD) study (n=9969; mean±standard deviation age=9.92±0.62 years; 47.1% female). Saliva samples were used for genotyping, and caregivers reported on their child's anxiety symptoms and trauma exposure. Fractional anisotropy (FA), a nonspecific measure of white matter integrity, was estimated for frontolimbic tracts.

Results:

Thirty-six percent of youth experienced one or more potentially traumatic events according to DSM-5 Criterion A (64% controls), and 45% were FAAH A-allele carriers (55% noncarriers). Relative to controls, trauma-exposed youth demonstrated higher anxiety and higher FA of the left uncinate. The FAAH A-allele (vs. CC) was associated with lower FA in the left fornix and left parahippocampal cingulum, and there was an indirect effect of FAAH genotype on anxiety through FA of the left fornix. Moreover, genotype moderated the association between FA of the left cingulum and anxiety.

Conclusions:

Our findings demonstrate distinct effects of trauma exposure and the FAAH C385A variant on frontolimbic pathways and subsequent anxiety risk in preadolescent children. This line of work may provide important insights into neurodevelopmental mechanisms leading to anxiety risk, and potential targets for intervention.

Introduction

The endocannabinoid (eCB) system plays a key role in modulating brain development throughout the life span.^1,2 During the prenatal period, the eCB system regulates synaptogenesis, neural progenitor differentiation, and axonal migration.³ Postnatally, eCB levels change dynamically across childhood and adolescence, and regulate activity in neural circuits, including myelination.⁴ In particular, the eCB system modulates the maturation of frontolimbic pathways that are rich in cannabinoid type 1 receptors, and regulate stress- and anxiety-related behaviors.^2,5 Cross-species studies show that frontolimbic brain circuitry demonstrates a protracted maturational course across childhood and adolescence, and is sensitive to environmental stress.^6–8 Early disruptions to frontolimbic development are thought to have long-term consequences for mental health.⁹

One potent form of environmental stress is childhood trauma exposure, such as violence, abuse, or accidental injury. Trauma exposure is common among youth—affecting up to two-thirds of adolescents^10,11—and is a chief risk factor for anxiety and other psychopathologies throughout the life span.^12,13 Neuroimaging studies demonstrate that childhood trauma exposure is associated with aberrant maturation of frontolimbic circuits, including reduced gray and white matter volumes, and altered microstructural integrity of frontolimbic white matter pathways.^14–17 Indeed, diffusion tensor imaging (DTI) studies have been used to measure microstructural integrity of white matter using fractional anisotropy (FA), which is based on the directional diffusion of water molecules in fiber pathways, with values ranging from 0 to 1, wherein 0 indicates isotropic (i.e., nondirectional) and 1 indicates anisotropic (i.e., highly directional) diffusion.¹⁸

DTI studies frequently report altered FA of frontolimbic pathways in adults and youth with histories of childhood trauma exposure, and in youth with post-traumatic stress disorder (PTSD).^5,14,18–23 Further, studies of childhood anxiety disorders demonstrate overlapping patterns of altered frontolimbic FA,²⁴ suggesting that altered maturation of frontolimbic pathways may be a common pathway linking childhood trauma with anxiety risk. For example, alterations in white matter integrity may influence functioning of neuronal circuits implicated in anxiety risk.

Emerging data indicate that the eCB system serves as “stress buffer,” and may protect against stress-related changes in frontolimbic circuitry and elevated anxiety risk.^25,26 For example, a common variant (C385A) in the gene encoding fatty acid amide hydrolase (FAAH)—the enzyme that catabolizes eCBs—is linked to lower central binding to the FAAH enzyme, higher circulating eCB levels, elevated resting-state functional connectivity within frontolimbic circuitry, and lower anxiety.^27,28 Similarly, a cross-species study by Mayo et al²⁹ found that the FAAH A-allele offered protection against stress-related decreases in eCB concentrations and increases in negative effect. Conversely, low eCB signaling is implicated in the pathophysiology of anxiety and other stress-related pathologies.³⁰ Behavioral or pharmacological interventions that boost eCB signaling are an area of active investigation for the prevention and treatment of anxiety and other mental disorders.^31–34

Although recent studies suggest that eCB signaling may protect against the negative effects of stress, few studies have focused on developing populations. This is a critical gap given that frontolimbic pathways develop across childhood and adolescence, corresponding with a sharp uptick in the onset of anxiety and other stress-related pathologies.³⁵ Further, preclinical evidence suggests that the eCB system changes dynamically across development,³⁶ and that early life stress blunts eCB signaling in frontolimbic regions (e.g., the hippocampus), which persists until adulthood.³⁷

Given these developmental changes, it is difficult to extrapolate findings from adult studies to youth. Understanding of how the eCB system and stress shape frontolimbic circuitry during development may open up novel approaches for preventing psychopathology before it begins. To our knowledge, only two studies have explored the impact of FAAH genotype on anxiety and frontolimbic brain circuitry in children and/or adolescents. In an elegant cross-species study, Gee et al. linked the FAAH C385A variant to lower anxiety and higher FA of the uncincate fasciculus; however, these main effects only emerged after age 12.³⁸

A recent study by Sisk et al³⁹ explored effects of FAAH on anxiety and large-scale resting-state brain networks in the Adolescent Brain Cognitive Development (ABCD) study, an ongoing neuroimaging study of >10,000 youth across 21 sites in the United States.⁴⁰ In their analysis of 3,109 9- to 11-year-old children from the ABCD study, Sisk et al³⁹ identified main effects of FAAH on connectivity of a distributed brain network, which included frontolimbic regions. Consistent with the earlier study by Gee et al., there were no main effects of FAAH genotype on anxiety in children (<12 years old). There was, however, an interaction between FAAH and connectivity in predicting anxiety scores, such that youth with the CC genotype with connectivity that more closely resembled that of A-alleles showed lower anxiety.³⁹ However, no studies have tested whether FAAH protects against the effects of childhood trauma exposure on frontolimbic white matter pathways.

Here, we leveraged the ABCD data set to examine the impact of the FAAH C385A polymorphism, childhood trauma exposure, and anxiety and microstructure of frontolimbic white matter pathways in 9- to 11-year-old children. We tested for both main and interactive effects of FAAH genotype and trauma, and additionally tested for overlapping effects of anxiety symptoms on frontolimbic pathways.

We hypothesized that (1) compared with control youth, trauma-exposed children would demonstrate elevated anxiety symptoms and differences in white matter integrity in frontolimbic regions, following prior work summarized above. Given evidence that effects of FAAH on anxiety and FA of the uncincate do not emerge until age 12,³⁹ we did not expect to find main effects of FAAH on anxiety or frontolimbic FA in this preadolescent sample. We did, however, hypothesize that (2) the FAAH C385A (associated with elevated eCB concentrations) would protect against the effects of trauma exposure on anxiety and frontolimbic FA (i.e., trauma-by-FAAH interaction), and (3) frontolimbic FA would interact with FAAH to predict anxiety in youth, suggesting a possible brain phenotype linking anxiety with eCB signaling.³⁸

Of note, the ABCD study was not designed with in-depth measures of traumatic experiences and trauma-related symptoms. However, as one of the largest “population neuroscience” studies of brain development, the ABCD cohort provides a unique opportunity to examine the impact of trauma exposure and genetic variation in FAAH on the brain in a community-based sample.

Materials and Methods

Participants, trauma, and anxiety

This study leveraged data from 9969 children from the ABCD study (Table 1 and Supplementary Data).^41,42 All participants provided written informed consent or oral assent and all study procedures were approved by the local and central institutional review boards. Caregivers reported on their child's trauma exposure using the PTSD Criterion A Traumatic Events Screener⁴³ from The Kiddie Schedule for Affective Disorders and Schizophrenia (K-SADS) for DSM-5,⁴⁴ and anxiety symptoms using the Child Behavior Checklist (CBCL).⁴⁸ We used the DSM-5–oriented anxiety subscale to measure continuous anxiety scores (standardized t-scores), and considered low- and high-anxiety groups based on cutoff scores (≥60).⁴⁵

Table 1.

Sample Demographics: Overall, by Trauma Group, and Genotype

Group	Overall (N=9969)	Trauma-exposed (n=3563)	Controls (n=6406)	p	FAAH A-allele carriers (n=4329)	FAAH CC genotype (n=5640)	p
Age (in years), mean (SD)	9.92 (0.62)	9.93 (0.62)	9.91 (0.62)	0.18	9.92 (0.62)	9.92 (0.62)	0.63
Female sex, n (%)	4699 (47.1)	1717 (48.2)	2982 (46.5)	0.12	2013 (46.5)	(47.6)	0.26
Race/ethnicity, n (%)				<0.001			<0.001
White	5259 (55.6)	1728 (51.2)	3531 (58.1)		1952 (47.7)	3307 (61.7)
Black	1330 (14.1)	583 (17.3)	747 (12.3)		786 (19.2)	544 (10)
Hispanic	1737 (18.4)	629 (18.6)	1108 (18.2)		861 (21)	876 (16.3)
Asian	130 (1.4)	30 (0.8)	100 (1.6)		41 (1)	89 (1.6)
Other	998 (10.6)	407 (12)	591 (9.7)		451 (11)	547 (10.2)
Anxiety symptoms, mean (SD)	53.4 (6)	54.4 (7.1)	52.8 (5.3)	<0.001	53.38 (6.08)	53.43 (6.01)	0.706
Anxiety groups, n (%)				<0.001			0.39
Low	8550 (85.7)	2883 (80.1)	5667 (88.5)		3728 (86.1)	4822 (85.5)
High (CBCL t-score >59)	1416 (14.2)	679 (19)	737 (11.5)		600 (13.9)	816 (14.5)
Maternal education, N (%)				<0.001			<0.001
Less than high school	569 (5.7)	117 (3.3)	392 (6.1)		308 (7.1)	261 (4.6)
High school or equivalent	2537 (26.5)	1133 (31.8)	1504 (23.5)		1241 (28.7)	1396 (24.8)
Bachelor's or Associate's	4187 (42.1)	1506 (42.3)	2681 (41.9)		1760 (40.7)	2427 (43.1)
Master's	1946 (19.5)	590 (16.6)	1356 (21.2)		781 (18.1)	1165 (20.7)
Doctorate	616 (6.2)	153 (4.3)	463 (7.2)		230 (5.3)	386 (6.8)
Annual family income, n (%)				<0.001			<0.001
<$50,000	2592 (28.3)	1161 (35.3)	1431 (24.4)		1342 (33.9)	1250 (24)
$50,000–$100,000	2606 (28.5)	958 (29.1)	1648 (28.1)		1081 (27.3)	1525 (29.3)
$100,000–$199,999	2870 (31.3)	898 (27.3)	1972 (33.6)		1125 (28.4)	1745 (33.6)
$200,000+	1090 (11.9)	271 (8.2)	819 (14)		410 (10.4)	680 (13.1)
Trauma exposure,^a n (%)	3563 (35.7)	3563 (100)	0 (0)	<0.001	1559 (36)	2004 (35.5)	0.62
DTI mean head motion in mm, mean (SD)	1.39 (0.57)	1.4 (0.55)	1.4 (0.59)	0.14	1.39 (0.58)	1.38 (0.57)	0.16

Bold numbers indicate significant group differences (p < 0.05). Annual family income is reported in US Dollars.

Number of types of potentially traumatic events experienced according to DSM-5 Criterion A.

CBCL, Child Behavior Checklist; DTI, diffusion tensor imaging; FAAH, fatty acid amide hydrolase; SD, standard deviation.

FAAH genotype

We focused on the FAAH C385A polymorphism (rs324420). Following prior work,^39,46,47 we characterized participants as A-alleles (i.e., AA or AC) or CC homozygotes. Importantly, FAAH genotype groups did not differ in trauma exposure (Table 1).

Frontolimbic white matter tracts

We focused on FA of the following ten frontolimbic white matter tracts (five tracts/hemisphere): fornix, uncinate fasciculus, cingulum bundle, parahippocampal cingulum, and inferior frontal occipital fasciculus (Fig. 1).

FIG. 1.

Frontolimbic white matter tracts of interest. Includes fornix (connecting the hippocampus and hypothalamus), uncinate fasciculus (connecting the inferior frontal lobe and anterior temporal lobe), cingulum bundle (connecting the cingulate gyrus and entorhinal cortex [cingulate portion]), parahippocampal cingulum (connecting the cingulate gyrus and entorhinal cortex [parahippocampal portion]), and inferior frontal occipital fasciculus (connecting the occipital lobe and frontal lobe).

Statistical analyses

Descriptive statistics were used to examine the prevalence of trauma exposure and distribution in FAAH genotype across the sample. We tested for effects of trauma and FAAH on demographic variables and anxiety symptoms. Variables that showed significant associations with trauma and/or FAAH genotype were included as covariates in subsequent analyses. Regression was used to test for main effects of FAAH genotype, trauma-by-FAAH, and anxiety symptoms on FA for each white matter tract, controlling for multiple comparisons. Following a recent article outlining best practices for control of covariates in the ABCD data set,⁴⁸ we used a tiered approach to covariates. We also conducted follow-up analyses to test for differences among the three gene groups (AA, AC, and CC). Mediation and moderation analyses were conducted for white matter pathways showing associations with both anxiety and FAAH genotype. See Supplementary Data for further details.

Results

Trauma exposure and FAAH

More than one-third (35.7%) of youth were exposed to one or more types of potentially traumatic events according to DSM-5 Criterion A. Trauma and control (no-trauma) groups differed in race/ethnicity, maternal education, and annual family income (Table 1). Therefore, these variables were included as “tier 2” covariates in subsequent regression models. Forty-five percent of youth were A-allele carriers; 55% were noncarriers.

Anxiety

Trauma-exposed youth showed higher anxiety as compared with control youth (Table 1). Similarly, trauma-exposed youth were more likely to exceed the cutoff for anxiety (Table 1). Therefore, anxiety was included as a “tier 3” covariate in subsequent regression analyses. There was no effect of FAAH (Table 1) or trauma-by-FAAH interaction on anxiety symptoms, nor proportion of children with elevated anxiety (p=0.39). There were also no differences between gene groups (AA, AC, and CC) in anxiety symptoms (p's>0.5).

Frontolimbic white matter

Main effects of trauma

With the inclusion of tier 1 covariates (age, sex at birth), trauma was positively associated with FA of the right cingulum bundle [overall model: F(3, 9452)=53.34, p<0.001; β=0.002, t=2.13, p=0.033], the left uncinate fasciculus [F(3, 9455)=10.52, p<0.001; β=0.002, t=3.1, p=0.002], and the right uncinate fasciculus [F(3, 9454)=10.19, p<0.001; β=0.001, t=2.05, p=0.04]. With the addition of tier 2 covariates (race, household income, maternal education), trauma exposure was positively associated with FA of the left fornix [overall model: F(6, 8633)=19.85, p<0.001; β=0.001, t=2.03, p=0.042], right fornix [F(6, 8633)=15.26, p<0.001; β=0.002, t=2.25, p=0.025], right parahippocampal cingulum [F(6, 8633)=6.13, p<0.001; β=0.002, t=2.36, p=0.018], and left uncinate [F(6, 8633)=6.06, p<0.001; β=0.002, t=2.87, p=0.004]. The left uncinate was the only tract that passed False Discovery Rate (FDR) correction and that remained significant when adding the tier 3 covariate [i.e., anxiety; overall model: F(7, 8631)=5.38, p<0.001; β=0.002, t=2.87, p=0.004; see Fig. 2a]. Trauma exposure was not associated with FA of other pathways.

FIG. 2.

Main effects of trauma exposure (a) and FAAH genotype (b) on frontolimbic white matter. *Indicates significant main effect. Statistical analyses performed using multiple regression; displayed here as groups for visualization. Error bars represent standard error. *p<0.05. FAAH, fatty acid amide hydrolase; L, left hemisphere.

Main effects of FAAH

With the inclusion of tier 1 covariates, the FAAH C385A variant was associated with lower FA in the left fornix [overall model: F(3, 9455)=27.43, p<0.001; β=0.002, t=3.5, p<0.001], right fornix [F(3, 9455)=26.04, p<0.001; β=0.002, t=2.5, p=0.01], right [F(3, 9455)=9.944, p<0.001; β=0.002, t=2.37, p=0.02], and left parahippocampal cingulum [F(3, 9453)=16.41, p<0.001; β=0.003, t=3.59, p<0.001]. With the addition of tier 2 covariates, the FAAH C385A variant was associated with lower FA of the left fornix [F(6, 8633)=20.12, p<0.001; β=0.001, t=2.39, p=0.017] and left parahippocampal cingulum [F(6, 8631)=13.25, p<0.001; β=0.002, t=2.64, p=0.008; Fig. 2b].

The left fornix [F(7, 8631)=18.36, p<0.001; β=0.001, t=2.37, p=0.018] and left parahippocampal cingulum [overall model: F(7, 8629)=11.55, p<0.001; β=0.002, t=2.67, p=0.008] both remained significant when adding the tier 3 covariate (Fig. 2b) but neither passed FDR correction. Follow-up analyses comparing the three gene groups showed significant differences in left fornix FA only for AC versus CC gene groups [F(7, 8809)=18.2, p<0.001; β=0.027, t=2.14, p=0.017]. No other gene groups were significant with the addition of tier 3 covariates. FAAH genotype was not associated with FA in other frontolimbic pathways.

Trauma-by-FAAH interactions

With the inclusion of tier 2 covariates, there were no significant trauma-by-FAAH genotype interactions on frontolimbic FA (F change p's>0.9).

Main effects of anxiety symptoms

With the inclusion of tier 1 covariates, anxiety was not associated with FA in any of the tested frontolimbic pathways (p's>0.1). With the addition of tier 2 covariates, anxiety was positively associated with FA in the left fornix [F(6, 8631)=20.47, p<0.001, β=0.03, t=2.78, p=0.005; see Fig. 3a]. Controlling for effects of trauma exposure and FAAH genotype (tier 3), anxiety remained a significant positive predictor of FA in the left fornix [F(8, 8631)=16.42, p<0.001, β=0.028, t=2.56, p=0.01], suggesting that results are robust to trauma and FAAH. Results for the left fornix passed FDR correction and remained significant when considering anxiety as a group variable (low, high) rather than a continuous variable (F(8, 8631)=16.18, p<0.001, β=0.023, t=2.16, p=0.031).

FIG. 3.

Effects of anxiety symptoms (a) on white matter integrity of the left fornix. (b) FA of the left fornix mediates the association between FAAH genotype and anxiety symptoms. Unstandardized coefficients are reported for direct effects, and partially standardized indirect effects are shown. *p<0.05, **p<0.01. FA, fractional anisotropy.

Mediation

We explored indirect effects of FAAH on anxiety through variation in FA. We focused on FA of the left fornix given the observed main effects of both anxiety and FAAH on this pathway. With the inclusion of tier 2 variables, there were significant indirect effects of FAAH genotype on anxiety through FA of the left fornix (β=0.0093, boot standard error [SE]=0.0054, lower level confidence interval [LLCI]=0.0008, upper level confidence interval [ULCI]=0.0218; partially standardized β=0.0015, boot SE=0.0009, LLCI=0.0001, ULCI=0.003; see Fig. 3b).

Reversal of the model (FAAH predicting fornix FA through anxiety) was not significant (LLCI=−0.0003, ULCI=0.00005) indicating that fornix FA mediated the associated between FAAH and anxiety but not the reverse. Results remained consistent when considering anxiety as a group (low, high) rather than a continuous variable (LLCI=0.0009, ULCI=0.022). The indirect effect for FA of left parahippocampal cingulum was not significant (LLCI=−0.0036, ULCI=0.0135).

Moderation

Given that a prior study demonstrated interactive effects of FAAH and functional connectivity in predicting anxiety in the ABCD sample,³⁹ we explored whether similar interactive effects exist for structural connectivity. With the inclusion of tier 2 variables, there was a significant interaction between FAAH genotype and left cingulum FA in predicting anxiety, [F(8, 8623)=1.41, p<0.001, b=0.95, t=2.82, p=0.0048; Fig. 4]. This effect was driven by a positive association between FA and anxiety in youth with the CC genotype (b=5.33, t=2.83, p=0.0047), but no association between FA and anxiety among A-alleles (b=−2.62, t=−1.2, p=0.21). These results passed FDR correction and remained significant when considering anxiety as a group rather than a continuous variable (p=0.02). No other pathways showed significant interactive effects with FAAH.

FIG. 4.

Interactive effects of FAAH genotype and FA of the left cingulum on anxiety symptoms. (a) It shows interaction effect of FAAH genotype-by-FA on anxiety, (b) shows a schematic of the association. Follow-up analyses showed that the interaction was driven by positive effects of FA on anxiety within the FAAH CC (but not A-allele) group. Unstandardized coefficients are reported. *p<0.05.

Discussion

This study tested the hypothesis that the FAAH C385A variant—associated with higher eCB signaling—buffers the effects of childhood trauma on anxiety and frontolimbic pathways in 9- to 11-year-old children. We did not find evidence for interactive effects of trauma exposure and FAAH genotype on childhood anxiety symptoms nor frontolimbic white matter microstructure. We did, however, observe distinct effects of trauma exposure and FAAH genotype on anxiety and frontolimbic white matter. In particular, trauma-exposed youth (vs. controls) showed elevated anxiety and higher FA of the left uncincate. The FAAH A-allele (vs. CC genotype) was associated with lower FA in the left fornix and left parahippocampal cingulum, and there was an indirect effect of FAAH genotype on anxiety through FA of the left fornix.

Moreover, FAAH genotype moderated the association between FA of the left cingulum bundle and anxiety, suggesting a possible brain phenotype of anxiety risk, which parallels the reported patterns observed in resting-state functional connectivity.³⁹ Together, these findings demonstrate that both trauma and the FAAH C385A variant impact frontolimbic circuitry and anxiety risk during preadolescence. In particular, alterations in white matter microstructure may influence functioning in neuronal circuits that govern stress and anxiety regulation. Results also add to prior studies, suggesting that the reported buffering effects of eCBs against stress-related effects on frontolimbic circuitry and anxiety risk emerge later, during adolescence (ages 12+).

We observed elevated anxiety in children with histories of trauma exposure relative to controls, which is consistent with the extant literature.^11,13 Neuroimaging studies also frequently report altered white matter microstructure of the uncincate after childhood trauma; however, the direction of these effects are inconsistent. Indeed, several studies report lower FA in trauma-exposed adolescents and adults with histories of childhood trauma as compared with controls.^20,49 Here, we observed higher FA in the uncincate in trauma-exposed children (vs. controls), which is consistent with a prior study in children in the same age range.⁵

Elevated FA of the uncincate in trauma-exposed youth may reflect enhancements within medial temporal-prefrontal pathways, which may contribute to altered hippocampal memory functioning.⁵⁰ The observed pattern is broadly consistent with prior studies reporting accelerated maturation of amygdala-prefrontal circuits following early life adversity, which may suggest an adaptive response.⁵¹ However, accelerated developmental may have consequences for later in life.⁵² Prior studies also show a shift in amygdala-prefrontal circuits around age 12, and that altered patterns of white matter neurodevelopment across childhood and adolescence may reflect psychiatric risk.^19,38 Therefore, microstructural alterations described in this article may reflect a brain phenotype that is specific to preadolescence.³⁸ Future waves of ABCD will provide better insights into whether the observed patterns are time limited or persistent.

We observed lower FA in A-alleles (vs. CC youth) in the left fornix and left parahippocampal cingulum, tracts that connect the hippocampus to the hypothalamus and medial prefrontal regions, respectively. Prior studies demonstrate that hippocampal-prefrontal circuits are critical for stress responding and emotion regulation,⁵³ including dampening amygdala output, fear extinction, and contextual processing.^54,55

Further, there is a high density of cannabinoid type 1 receptors in both the hippocampus and prefrontal cortex,⁵⁶ and a prior study in adults links genetic variation in eCB signaling to altered hippocampal activity during fear extinction.⁴⁷ Our findings demonstrate that FAAH genotype modulates frontolimbic pathways during preadolescence—earlier than previously demonstrated. We observed effects in the fornix and parahippocampal cingulum, which are implicated in fear, anxiety, and episodic memory.^57,58 We did not observe main effects of FAAH on FA of the uncincate, which is consistent with prior studies showing effects of FAAH on this pathway emerge after age 12.

We observed indirect (but not direct) effects of FAAH on anxiety in this preadolescent sample, which is consistent with prior studies showing that these effects emerge during adolescence.^38,39 Interestingly, we found evidence for an indirect association between FAAH and anxiety through white matter integrity of the fornix, which has been previously associated with anxiety risk in adults.⁵⁹ Similar to a recent study of functional connectivity in the ABCD sample,³⁹ we found that FAAH interacted with structural connectivity of the cingulum to predict anxiety. In both studies, the effects of brain connectivity on anxiety were only apparent with the CC group, suggesting that the A-allele (associated with elevated eCB signaling) may confer some benefit against anxiety. Given that altered FA in the cingulum is frequently reported in adults and youths with anxiety,⁵⁷ our findings suggest that FAAH modulates frontolimbic pathways involved in anxiety risk.

Strengths and limitations of this study warrant mention. Strengths of this study include the use of a large, nationwide study, and inclusion of both trauma and FAAH on anxiety and frontolimbic development. One limitation is that the proportion of youth with exposure to one or more types of potentially traumatic events was relatively low, which may limit comparison with other studies of trauma. For example, our prior community-based studies of lower income urban areas find higher rates of exposure among children of a similar age (e.g., 45%).⁶⁰

The relatively low rate of trauma in the baseline ABCD sample may be related to the high representation of youth from white and higher income families, or related to the age. Indeed, rates of trauma exposure have been shown to dramatically increase around age 12.¹¹ Therefore, future studies should aim to examine the effects of age-of-onset, trauma severity, frequency, or trauma types on frontolimbic development. Also, the mediation analyses are cross-sectional and should be considered exploratory. Future studies incorporating longitudinal releases of ABCD data should help distinguish between mediation and spuriousness (i.e., caused by another covariate) associations among trauma, anxiety, and FA.⁴⁸

Further, we relied on DTI, which is a nonspecific measure of white matter integrity. FA is influenced by a number of factors, including axon density, diameter, damage, myelination, and permeability, and by crossing fibers, fiber orientation, or number.^61,62 Therefore, future studies should employ different approaches to better characterize the observed effects. In addition, although the FAAH C385A variant has consistently associated with higher circulating levels of the eCB anandamide, there is variation in eCB levels within genotype groups. Future studies measuring circulating concentrations of eCBs in youth, particularly preadolescent youth, are needed.

Conclusions

This study builds on our knowledge of the neural correlates of anxiety risk in youth. In particular, our findings demonstrate distinct effects of trauma exposure and the FAAH C385A variant on white matter microstructure and subsequent anxiety risk in preadolescent children. This line of work should provide important insights into potential neurodevelopmental mechanisms leading to anxiety risk, and potential targets for intervention.

Footnotes

Acknowledgments

The authors thank Austin Morales and Craig Peters for their assistance with accessing genetic data from the NIMH Data Archive (NDA) and with , respectively.

Authors' Contributions

H.A.M. contributed to conceptualization (lead); writing—original draft (lead); formal analysis (lead); writing—review and editing. J.E. and S.D. contributed to writing—review and editing. C.A.R. performed writing—review and editing; conceptualization (supporting). All authors approved the final version of the article.

Author Disclosure Statement

C.A.R. disclosed consulting fees from Lundbeck. All other authors reported no biomedical financial or potential conflicts of interest.

Funding Information

H.A.M. is supported by K01MH119241 and C.A.R. is supported by R33MH111935. Data used in the preparation of this article were obtained from the ABCD study (https://abcdstudy.org), held in the NDA. This is a multisite, longitudinal study designed to recruit >10,000 children age 9–10 and follow them over 10 years into early adulthood. The ABCD study is supported by the National Institutes of Health and additional federal partners under award numbers U01DA041022, U01DA041028, U01DA041048, U01DA041089, U01DA041106, U01DA041117, U01DA041120, U01DA041134, U01DA041148, U01DA041156, U01DA041174, U24DA041123, U24DA041147, U01DA041093, and U01DA041025. A full list of supporters is available at https://abcdstudy.org/nih-collaborators A listing of participating sites, and a complete listing of the study investigators can be found at investigators.html ABCD consortium investigators designed and implemented the study and/or provided data, but did not participate in analysis or writing of this report. This article reflects the views of the authors, and may not reflect the opinions or views of the NIH or ABCD consortium investigators. The ABCD data repository grows and changes over time.

Supplementary Material

Abbreviations Used

References

Harkany

, Guzmán

, Galve-Roperh

, et al. The emerging functions of endocannabinoid signaling during CNS development. Trends Pharmacol Sci, 2007; 28(2):83–92; doi: 10.1016/j.tips.2006/12.004

Meyer

, Lee

, Gee

. The role of the endocannabinoid system and genetic variation in adolescent brain development. Neuropsychopharmacology, 2018; 43(1):21–33; doi: 10.1038/npp.2017.143

Fride

, Gobshtis

, Dahan

, et al. Chapter 6 the endocannabinoid system during development: Emphasis on perinatal events and delayed effects. Vitam Horm, 2009; 81:139–158; doi: 10.1016/S0083-6729(09)81006-6

Ilyasov

, Milligan

, Pharr

, et al. The endocannabinoid system and oligodendrocytes in health and disease. Front Neurosci, 2018; 12:733; doi: 10.3389/fnins.2018.00733

Granger

, Glynn

, Sandman

, et al. Aberrant maturation of the uncinate fasciculus follows exposure to unpredictable patterns of maternal signals. J Neurosci, 2021; 41(6):1242–1250; doi: 10.1523/JNEUROSCI.0374-20.2020

Lebel

, Walker

, Leemans

, et al. Microstructural maturation of the human brain from childhood to adulthood. Neuroimage, 2008; 40(3):1044–1055; doi: 10.1016/j.neuroimage.2007.12.053

Burns

, Van Laere

, Sanabria-Bohórquez

, et al. [18F]MK-9470, a positron emission tomography (PET) tracer for in vivo human PET brain imaging of the cannabinoid-1 receptor. Proc Natl Acad Sci U S A, 2007; 104(23):9800–9805; doi: 10.1073/pnas.0703472104

Tottenham

. Early adversity and the neotenous human brain. Biol Psychiatry, 2020; 87(4):350–358; doi: 10.1016/j.biopsych.2019.06.018

Tottenham

, Sheridan

. A review of adversity, the amygdala and the hippocampus: A consideration of developmental timing. Front Hum Neurosci, 2010; 3:68; doi: 10.3389/neuro.09.068.2009

10.

Copeland

, Keeler

, Angold

, et al. Traumatic events and posttraumatic stress in childhood. Arch Gen Psychiatry, 2007; 64(5):577–584.

11.

McLaughlin

, Koenen

, Hill

, et al. Trauma exposure and posttraumatic stress disorder in a national sample of adolescents. J Am Acad Child Adolesc Psychiatry, 2013; 52(8):815.e14–830.e14; doi: 10.1016/j.jaac.2013.05.011

12.

Copeland

, Shanahan

, Hinesley

, et al. Association of childhood trauma exposure with adult psychiatric disorders and functional outcomes. JAMA Netw Open, 2018; 1(7):e184493; doi: 10.1001/jamanetworkopen.2018.4493

13.

McLaughlin

, Green

, Gruber

, et al. Childhood adversities and first onset of psychiatric disorders in a national sample of US adolescents. Arch Gen Psychiatry, 2012; 69(11):1151–1160; doi: 10.1001/archgenpsychiatry.2011.2277

14.

Daniels

, Lamke

, Gaebler

, et al. White matter integrity and its relationship to PTSD and childhood trauma—A systematic review and meta-analysis. Depress Anxiety, 2013; 69(11):1151–1160; doi: 10.1001/archgenpsychiatry.2011.2277

15.

Lim

, Radua

, Rubia

. Gray matter abnormalities in childhood maltreatment: A voxelwise meta-analysis. Am J Psychiatry, 2014; 171(8):854–863; doi: 10.1176/appi.ajp.2014.13101427

16.

Begemann

MJH

, Schutte

MJL

, Van Dellen

, et al. Childhood trauma is associated with reduced frontal gray matter volume: A large transdiagnostic structural MRI study. Psychol Med, 2021; 1–9; doi: 10.1017/S0033291721002087

17.

Cassiers

LLM

, Sabbe

BGC

, Schmaal

, et al. Structural and functional brain abnormalities associated with exposure to different childhood trauma subtypes: A systematic review of neuroimaging findings. Front Psychiatry, 2018; 9:329; doi: 10.3389/fpsyt.2018.00329

18.

Basser

. Inferring microstructural features and the physiological state of tissues from diffusion-weighted images. NMR Biomed, 1995; 8(7–8):333–344; doi: 10.1002/nbm.1940080707

19.

Russell

, Heyn

, Herringa

. Pediatric PTSD is characterized by age and sex-related abnormalities in structural connectivity. Biol Psychiatry, 2021; 46(12):2217–2223; doi: 10.1038/s41386-021-01083-6

20.

McCarthy-Jones

, Oestreich

LKL

, Lyall

, et al. Childhood adversity associated with white matter alteration in the corpus callosum, corona radiata, and uncinate fasciculus of psychiatrically healthy adults. Brain Imaging Behav, 2018; 12(2):449–458; doi: 10.1007/s11682-017-9703-1

21.

Hanson

, Adluru

, Chung

, et al. Early neglect is associated with alterations in white matter integrity and cognitive functioning. Child Dev, 2013; 84(5):1566–1578; doi: 10.1111/cdev.12069

22.

Choi

, Jeong

, Rohan

, et al. Preliminary evidence for white matter tract abnormalities in young adults exposed to parental verbal abuse. Biol Psychiatry, 2009; 65(3):227–234; doi: 10.1016/j.biopsych.2008.06.022

23.

Eluvathingal

, Chugani

, Behen

, et al. Abnormal brain connectivity in children after early severe socioemotional deprivation: A diffusion tensor imaging study. Pediatrics, 2006; 117(6):2093–2100; doi: 10.1542/peds.2005-1727

24.

Tromp

DPM

, Williams

, Fox

, et al. Altered uncinate fasciculus microstructure in childhood anxiety disorders in boys but not girls. Am J Psychiatry, 2019; 176(3):208–216; doi: 10.1176/appi.ajp.2018.18040425

25.

Morena

, Patel

, Bains

, et al. Neurobiological interactions between stress and the endocannabinoid system. Neuropsychopharmacology, 2016; 41(1):80–102; doi: 10.1038/npp.2015.166

26.

deRoon-Cassini

, Stollenwerk

, Beatka

, et al. Meet your stress management professionals: The endocannabinoids. Trends Mol Med, 2020; 26(10):953–968; doi: 10.1016/j.molmed.2020.07.002

27.

Dincheva

, Drysdale

, Hartley

, et al. FAAH genetic variation enhances fronto-amygdala function in mouse and human. Nat Commun, 2015; 6:6395; doi: 10.1038/ncomms7395

28.

Boileau

, Rusjan

, Williams

, et al. Blocking of fatty acid amide hydrolase activity with PF-04457845 in human brain: A positron emission tomography study with the novel radioligand [11C]CURB. J Cereb Blood Flow Metab, 2015; 35(11):1827–1835; doi: 10.1038/jcbfm.2015.133

29.

Mayo

, Asratian

, Lindé

, et al. Protective effects of elevated anandamide on stress and fear-related behaviors: Translational evidence from humans and mice. Mol Psychiatry, 2020; 25(5):993–1005; doi: 10.1038/s41380-018-0215-1

30.

Hill

, Campolongo

, Yehuda

, et al. Integrating endocannabinoid signaling and cannabinoids into the biology and treatment of posttraumatic stress disorder. Neuropsychopharmacology, 2018; 43(1):80–102; doi: 10.1038/npp.2017.162

31.

Desai

, Borg

, Cuttler

, et al. A systematic review and meta-analysis on the effects of exercise on the endocannabinoid system. Cannabis Cannabinoid Res, 2022; 7(4):388–408; doi: 10.1089/can.2021.0113

32.

Mayo

, Rabinak

, Hill

, et al. Targeting the endocannabinoid system in the treatment of PTSD: A promising case of preclinical-clinical translation?. Biol Psychiatry, 2022; 91(3):262–272; doi: 10.1016/j.biopsych.2021.07.019

33.

Rabinak

, Angstadt

, Sripada

, et al. Cannabinoid facilitation of fear extinction memory recall in humans. Neuropharmacology, 2013; 64:396–402; doi: 10.1016/j.neuropharm.2012.06.063

34.

Mayo

, Asratian

, Lindé

, et al. Elevated anandamide, enhanced recall of fear extinction, and attenuated stress responses following inhibition of fatty acid amide hydrolase: A randomized, controlled experimental medicine trial. Biol Psychiatry, 2020; 87(6):538–547; doi: 10.1016/j.biopsych.2019.07.034

35.

Kessler

, Berglund

, Demler

, et al. Lifetime prevalence and age-of-onset distributions of DSM-IV disorders in the national comorbidity survey replication. Arch Gen Psychiatry, 2005; 62(6):593; doi: 10.1001/archpsyc.62.6.593

36.

Lee

TTY

, Hill

, Hillard

, et al. Temporal changes in N-acylethanolamine content and metabolism throughout the peri-adolescent period. Synapse, 2013; 67(1):4–10; doi: 10.1002/syn.21609

37.

Hill

, Eiland

, Lee

TTY

, et al. Early life stress alters the developmental trajectory of corticolimbic endocannabinoid signaling in male rats. Neuropharmacology, 2019; 146:154–162; doi: 10.1016/j.neuropharm.2018.11.036

38.

Gee

, Fetcho

, Jing

, et al. Individual differences in frontolimbic circuitry and anxiety emerge with adolescent changes in endocannabinoid signaling across species. Proc Natl Acad Sci U S A, 2016; 113(16):4500–4505; doi: 10.1073/pnas.1600013113

39.

Sisk

, Rapuano

, Conley

, et al. Genetic variation in endocannabinoid signaling is associated with differential network-level functional connectivity in youth. J Neurosci Res, 2021; 100(3):731–743; doi: 10.1002/jnr.24946

40.

Volkow

, Koob

, Croyle

, et al. The conception of the ABCD study: From substance use to a broad NIH collaboration. Dev Cogn Neurosci, 2018; 32:4–7; doi: 10.1016/j.dcn.2017.10.002.

41.

Jernigan

, Brown

, Dowling

. The Adolescent Brain Cognitive Development study. J Res Adolesc, 2018; 28(1):154–156; doi: 10.1111/jora.12374

42.

Casey

, Cannonier

, Conley

, et al. The Adolescent Brain Cognitive Development (ABCD) study: Imaging acquisition across 21 sites. Dev Cogn Neurosci, 2018; 32:43–54; doi: 10.1016/j.dcn.2018.03.001

43.

Hoffman

, Clark

, Orendain

, et al. Stress exposures, neurodevelopment and health measures in the ABCD study. Neurobiol Stress, 2019; 10:100157; doi: 10.1016/j.ynstr.2019.100157

44.

Achenbach

, Edelbrook

. Child Behavior Checklist (CBCL). Univ Assoc Psychiatry, 1983; 53(1):418–435.

45.

Petty

, Rosenbaum

, Hirshfeld-Becker

, et al. The Child Behavior Checklist broad-band scales predict subsequent psychopathology: A 5-year follow-up. J Anxiety Disord, 2008; 22(3):532–539; doi: 10.1016/j.janxdis.2007.04.003

46.

Hariri

, Gorka

, Hyde

, et al. Divergent effects of genetic variation in endocannabinoid signaling on human threat- and reward-related brain function. Biol Psychiatry, 2009; 66(1):9–16; doi: 10.1016/j.biopsych.2008.10.047

47.

Zabik

, Iadipaolo

, Marusak

, et al. A common genetic variant in fatty acid amide hydrolase is linked to alterations in fear extinction neural circuitry in a racially diverse, nonclinical sample of adults. J Neurosci Res, 2022; 100(3):744–761; doi: 10.1002/jnr.24860

48.

Dick

, Lopez

, Watts

, et al. Meaningful associations in the Adolescent Brain Cognitive Development study. Neuroimage, 2021; 239:118262; doi: 10.1016/j.neuroimage.2021.118262

49.

Hanson

, Knodt

, Brigidi

, et al. Lower structural integrity of the uncinate fasciculus is associated with a history of child maltreatment and future psychological vulnerability to stress. Dev Psychopathol, 2015; 27(4 Pt 2):1611–1619; doi: 10.1017/S0954579415000978

50.

Molet

, Maras

, Kinney-Lang

, et al. MRI uncovers disrupted hippocampal microstructure that underlies memory impairments after early-life adversity. Hippocampus, 2016; 26(12):1618–1632; doi: 10.1002/hipo.22661

51.

Gee

, Gabard-Durnam

, Flannery

, et al. Early developmental emergence of human amygdala-prefrontal connectivity after maternal deprivation. Proc Natl Acad Sci U S A, 2013; 110(39):15638–15643; doi: 10.1073/pnas.1307893110

52.

Callaghan

, Tottenham

. The Stress Acceleration Hypothesis: Effects of early-life adversity on emotion circuits and behavior. Curr Opin Behav Sci, 2016; 7:76–81; doi: 10.1016/j.cobeha.2015.11.018

53.

McEwen

. Brain on stress: How the social environment gets under the skin. Proc Natl Acad Sci U S A, 2012; 109(Suppl 2):17180–17185; doi: 10.1073/pnas.1121254109

54.

Kalisch

, Korenfeld

, Stephan

, et al. Context-dependent human extinction memory is mediated by a ventromedial prefrontal and hippocampal network. J Neurosci, 2006; 26(37):9503–9511; doi: 10.1523/JNEUROSCI.2021-06.2006

55.

Maren

, Phan

, Liberzon

. The contextual brain: Implications for fear conditioning, extinction and psychopathology. Nat Rev Neurosci, 2013; 14(6):417–428; doi: 10.1038/nrn3492

56.

Mackie

. Distribution of cannabinoid receptors in the central and peripheral nervous system. Handb Exp Pharmacol, 2005;(168):299–325; doi: 10.1007/3-540-26573-2_10

57.

Bubb

, Metzler-Baddeley

, Aggleton

. The cingulum bundle: Anatomy, function, and dysfunction. Neurosci Biobehav Rev, 2018; 92:104–127; doi: 10.1016/j.neubiorev.2018.05.008

58.

Benear

, Ngo

, Olson

. Dissecting the fornix in basic memory processes and neuropsychiatric disease: A review. Brain Connect, 2020; 10(7):331–354; doi: 10.1089/brain.2020.0749

59.

Modi

, Trivedi

, Singh

, et al. Individual differences in trait anxiety are associated with white matter tract integrity in fornix and uncinate fasciculus: Preliminary evidence from a DTI based tractography study. Behav Brain Res, 2013; 238:188–192; doi: 10.1016/j.bbr.2012.10.007

60.

Marusak

, Hehr

, Bhogal

, et al. Alterations in fear extinction neural circuitry and fear-related behavior linked to trauma exposure in children. Behav Brain Res, 2021; 398:112958; doi: 10.1016/j.bbr.2020.112958

61.

Winston

. The physical and biological basis of quantitative parameters derived from diffusion MRI. Quant Imaging Med Surg, 2012; 2(4):254–265; doi: 10.3978/j.issn.2223–4292.2012.12.05

62.

Jones

, Knösche

, Turner

. White matter integrity, fiber count, and other fallacies: The do's and don'ts of diffusion MRI. Neuroimage. 2013; 73:239–254; doi: 10.1016/j.neuroimage.2012.06.081

Supplementary Material

Please find the following supplemental material available below.

For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.

For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.

0.00 MB

0.04 MB