Supportive of diathesis–stress models of depression, twin research first documented that broad genetic vulnerability to depression (i.e., an unaffected twin whose co-twin has a history of depression) potentiates the depressogenic effects of stress. In 2003, Caspi and colleagues provided evidence of a molecular genetic × stress interaction predicting depression when they found that the short 5-HTTLPR allele was associated with greater risk for stress-related depression. This highly influential study inspired numerous replication and extension attempts that have produced conflicting findings, with even meta-analyses reaching opposing conclusions. Neuroscience evidence suggests that the 5-HTTLPR polymorphism may confer vulnerability to depression through its association with amygdala function and early life exposure to heightened serotonin levels. Given mixed evidence of the relationship between 5-HTTLPR and stress-related depression as well as putative intermediate phenotypes, further empirical investigation is warranted.

Word Count: 252 Introduction Word Count: 575/1000 Discussion Word Count: 1688/2000 Total Word Count: 4758/6000 Tables/Figures: 6/6 Number of References: 76/50 Date of Submission: 10/07/2016 Date of Resubmission: 01/03/2017 Hypothalamic-Pituitary-Adrenal Axis Genetic Variation and Early Stress Moderates Amygdala Function Christina R. Di Iorio, Caitlin E. Carey, 1 Lindsay J Michalski, Nadia S. Corral-Frias, 2 Emily Drabant Conley, Ahmad R. Hariri, Ryan Bogdan BRAIN Lab, Department of Psychology, Washington University in St. Louis, St. Louis, MO, USA 2 Department of Psychiatry, Washington University in St. Louis, St. Louis, MO, USA 3 23andMe Department of Psychology and Neuroscience, Duke University, Durham, NC, USA Neurosciences Program, Division of Biology and Biomedical Sciences, Washington University in St. Louis, St. Louis, MO, USA Molecular Genetics and Genomics Program, Division of Biology and Biomedical Sciences, Washington University in St. Louis, St. Louis, MO, USA Human and Statistical Genetics Program, Division of Biology and Biomedical Sciences, Washington University in St. Louis, St. Louis, MO, USA Corresponding authors: Christina Di Iorio & Ryan Bogdan WUSTL, Psych Bldg, CB 1125 One Brookings Drive St. Louis, MO 63130 Phone: 617-407-5645; email: crdiiorio@wustl.edu, rbogdan@wustl.edu, Highlights  HPA axis genetic profile and early life stress interact to predict amygdala function  HPA axis genetic profile is associated with anxiety symptoms  Within system genetic profiles may inform our understanding of psychopathology DIIORIO HPA BIOLOGICALLY-INFORMED MULTILOCUS PROFILE 2

Early life stress may precipitate psychopathology, at least in part, by influencing amygdala function. Converging evidence across species suggests that links between childhood stress and amygdala function may be dependent upon hypothalamic-pituitary-adrenal (HPA) axis function. Using data from college-attending non-Hispanic European-Americans (n=308) who completed the Duke Neurogenetics Study, we examined whether early life stress (ELS) and HPA axis genetic variation interact to predict threat-related amygdala function as well as psychopathology symptoms. A biologically-informed multilocus profile score (BIMPS) captured HPA axis genetic variation (FKBP5 rs1360780, CRHR1 rs110402; NR3C2 rs5522/rs4635799) previously associated with its function (higher BIMPS are reflective of higher HPA axis activity). BOLD fMRI data were acquired while participants completed an emotional face matching task. ELS and depression and anxiety symptoms were measured using the childhood trauma questionnaire and the mood and anxiety symptom questionnaire, respectively. The interaction between HPA axis BIMPS and ELS was associated with right amygdala reactivity to threat-related stimuli, after accounting for multiple testing (empirical-p=0.016). Among individuals with higher BIMPS (i.e., the upper 21.4%), ELS was positively coupled with threat-related amygdala reactivity, which was absent among those with average or low BIMPS. Further, higher BIMPS were associated with greater self-reported anxious arousal, though there was no evidence that amygdala function mediated this relationship. Polygenic variation linked to HPA axis function may moderate the effects of early life stress on threat-related amygdala function and confer risk for anxiety symptomatology. However, what, if any, neural mechanisms may mediate the relationship between HPA axis BIMPS and anxiety symptomatology remains unclear.

A haplotype in the gene encoding interleukin-18 (IL-18), associated with higher expression of the pro-inflammatory cytokine IL-18, predicts increased risk of developing depression in response to stress. Given prior evidence that inflammation is associated with altered ventral striatum response to reward and punishment, we hypothesized that the IL-18 haplotype would be associated with individual differences in ventral striatum response to positive and negative feedback in a card guessing game associated with monetary reward in young adults.

Defects in experiencing disgust may contribute to obesity by allowing for the overconsumption of food. However, the relationship of disgust proneness and its associated neural locus has yet to be explored in the context of obesity. Thirty-three participants (17 obese, 16 lean) completed the Disgust Propensity and Sensitivity Scale-Revised and a functional magnetic resonance imaging paradigm where images from 4 categories (food, contaminates, contaminated food or fixation) were randomly presented. Independent two-sample t-tests revealed significantly lower levels of Disgust Sensitivity for the obese group (mean score = 14.7) compared with the lean group (mean score = 17.6, P = 0.026). The obese group had less activation in the right insula than the lean group when viewing contaminated food images. Multiple regression with interaction analysis revealed one left insula region where the association of Disgust Sensitivity scores with activation differed by group when viewing contaminated food images. These interaction effects were driven by the negative correlation of Disgust Sensitivity scores with beta values extracted from the left insula in the obese group (r = -0.59) compared with a positive correlation in the lean group (r = 0.65). Given these body mass index-dependent differences in Disgust Sensitivity and neural responsiveness to disgusting food images, it is likely that altered Disgust Sensitivity may contribute to obesity.

Common functional polymorphisms in the gene encoding interleukin-18 (IL18), a cytokine belonging to the IL-1 superfamily that can induce synthesis of several other cytokines, have been associated with major depressive episodes following the experience of stressful life events. The neural mechanisms underlying these associations remain unexamined. Here we use an imaging genetics strategy to examine the effects of risk-related IL18 haplotypes comprising rs187238 and rs1946518 on threat-related amygdala reactivity and, through an indirect effect, stress-related symptoms of depression and anxiety in 448 non-Hispanic Caucasian university students. Analyses indicated that women but not men possessing an IL18 haplotype comprising both risk-related alleles evidenced increased threat-related left centromedial amygdala reactivity relative to other haplotype groups. Moreover, in women only, increased threat-related left centromedial amygdala reactivity predicted increased symptoms of depression and anxiety in individuals also reporting higher levels of life stress. Path analyses revealed a significant indirect effect of IL18 risk haplotype on symptoms of depression and anxiety through increased threat-related amygdala reactivity. These results suggest that a common functional IL18 haplotype associated with heightened proinflammatory responses confers susceptibility to stress-related depression and anxiety through effects on threat-related amygdala function, a risk pathway specific to women. If replicated, these patterns can inform the search for personalized interventions targeting neurobiological pathways of risk associated with inflammation.

Advancing Translational Sciences, Grant 2 [UL1 TR000445-06]. Its contents are solely the responsibility of the authors and do not necessarily represent official views of the National Institutes of Health. ABSTRACT Defects in experiencing disgust may contribute to obesity by allowing for the overconsumption of food. However, the relationship of disgust proneness and its associated neural locus has yet to be explored in the context of obesity. Thirty-three participants (17 obese; 16 lean) completed the Disgust Propensity and Sensitivity Scale-Revised (DPSS-R) and an fMRI paradigm where images from four categories (food, contaminates, contaminated food, or fixation) were randomly presented. Independent two-sample t-tests revealed significantly lower levels of Disgust Sensitivity for the obese group (mean score=14.7) compared to the lean group (mean score=17.6), p=0.026. The obese group had less activation in the right insula than the lean group when viewing contaminated food images. Multiple regression with interaction analysis revealed one left insula region where the association of Disgust Sensitivity scores with activation differed by group when viewing contaminated food images. These interaction effects were driven by the negative correlation of Disgust Sensitivity scores with beta values extracted from the left insula in the obese group (r=-0.59) compared to a positive correlation in the lean group (r=0.65). Given these BMI-dependent differences in Disgust Sensitivity and neural responsiveness to disgusting food images it is likely that altered Disgust Sensitivity may contribute to obesity.

Ecstasy (3,4-methylenedioxymethamphetamine [MDMA]) polydrug users have verbal memory performance that is statistically significantly lower than that of control subjects. Studies have correlated long-term MDMA use with altered brain activation in regions that play a role in verbal memory.The aim of our study was to examine the association of lifetime ecstasy use with semantic memory performance and brain activation in ecstasy polydrug users.A total of 23 abstinent ecstasy polydrug users (age = 24.57 years) and 11 controls (age = 22.36 years) performed a two-part functional magnetic resonance imaging (fMRI) semantic encoding and recognition task. To isolate brain regions activated during each semantic task, we created statistical activation maps in which brain activation was greater for word stimuli than for non-word stimuli (corrected p < 0.05).During the encoding phase, ecstasy polydrug users had greater activation during semantic encoding bilaterally in language processing regions, including Brodmann areas 7, 39, and 40. Of this bilateral activation, signal intensity with a peak T in the right superior parietal lobe was correlated with lifetime ecstasy use (r (s) = 0.43, p = 0.042). Behavioral performance did not differ between groups.These findings demonstrate that ecstasy polydrug users have increased brain activation during semantic processing. This increase in brain activation in the absence of behavioral deficits suggests that ecstasy polydrug users have reduced cortical efficiency during semantic encoding, possibly secondary to MDMA-induced 5-HT neurotoxicity. Although pre-existing differences cannot be ruled out, this suggests the possibility of a compensatory mechanism allowing ecstasy polydrug users to perform equivalently to controls, providing additional support for an association of altered cerebral neurophysiology with MDMA exposure.

The serotonergic neurotoxin, 3,4-methylenedioxymethamphetamine (MDMA/Ecstasy), is a highly popular recreational drug. Human recreational MDMA users have neurocognitive and neuropsychiatric impairments, and human neuroimaging data are consistent with animal reports of serotonin neurotoxicity. However, functional neuroimaging studies have not found consistent effects of MDMA on brain neurophysiology in human users. Several lines of evidence suggest that studying MDMA effects in visual system might reveal the general cortical and subcortical neurophysiological consequences of MDMA use. We used 3 T functional magnetic resonance imaging during visual stimulation to compare visual system lateral geniculate nucleus (LGN) and Brodmann Area (BA) 17 and BA 18 activation in 20 long abstinent (479.95±580.65 days) MDMA users and 20 non-MDMA user controls. Lifetime quantity of MDMA use was strongly positively correlated with blood oxygenation level-dependent (BOLD) signal intensity in bilateral LGN (rs=0.59; p=0.007), BA 17 (rs=0.50; p=0.027), and BA 18 (rs=0.48; p=0.031), and with the spatial extent of activation in BA 17 (rs=0.059; p=0.007) and BA 18 (rs=0.55; p=0.013). There were no between-group differences in brain activation in any region, but the heaviest MDMA users showed a significantly greater spatial extent of activation than controls in BA 17 (p=0.031) and BA 18 (p=0.049). These results suggest that human recreational MDMA use may be associated with a long-lasting increase in cortical excitability, possibly through loss of serotonin input to cortical and subcortical regions. When considered in the context of previous results, cortical hyper-excitability may be a biomarker for MDMA-induced serotonin neurotoxicity.

CONTEXT MDMA (3,4-methylenedioxymethamphetamine, also popularly known as "ecstasy") is a popular recreational drug that produces loss of serotonin axons in animal models. Whether MDMA produces chronic reductions in serotonin signaling in humans remains controversial. OBJECTIVE To determine whether MDMA use is associated with chronic reductions in serotonin signaling in the cerebral cortex of women as reflected by increased serotonin(2A) receptor levels. DESIGN Cross-sectional case-control study comparing serotonin(2A) receptor levels in abstinent female MDMA polydrug users with those in women who did not use MDMA (within-group design assessing the association of lifetime MDMA use and serotonin(2A) receptors). Case participants were abstinent from MDMA use for at least 90 days as verified by analysis of hair samples. The serotonin(2A) receptor levels in the cerebral cortex were determined using serotonin(2A)-specific positron emission tomography with radioligand fluorine 18-labeled setoperone as the tracer. SETTING Academic medical center research laboratory. PARTICIPANTS A total of 14 female MDMA users and 10 women who did not use MDMA (controls). The main exclusion criteria were nondrug-related DSM-IV Axis I psychiatric disorders and general medical illness. MAIN OUTCOME MEASURES Cortical serotonin(2A) receptor nondisplaceable binding potential (serotonin(2A)BP(ND)). RESULTS MDMA users had increased serotonin(2A)BP(ND) in occipital-parietal (19.7%), temporal (20.5%), occipitotemporal-parietal (18.3%), frontal (16.6%), and frontoparietal (18.5%) regions (corrected P < .05). Lifetime MDMA use was positively associated with serotonin(2A)BP(ND) in frontoparietal (β = 0.665; P = .007), occipitotemporal (β = 0.798; P = .002), frontolimbic (β = 0.634; P = .02), and frontal (β = 0.691; P = .008) regions. In contrast, there were no regions in which MDMA use was inversely associated with receptor levels. There were no statistically significant effects of the duration of MDMA abstinence on serotonin(2A)BP(ND). CONCLUSIONS The recreational use of MDMA is associated with long-lasting increases in serotonin(2A) receptor density. Serotonin(2A) receptor levels correlate positively with lifetime MDMA use and do not decrease with abstinence. These results suggest that MDMA use produces chronic serotonin neurotoxicity in humans. Given the broad role of serotonin in human brain function, the possibility for therapeutic MDMA use, and the widespread recreational popularity of this drug, these results have critical public health implications.