Amygdala function and 5-HTT gene variants in adolescent anxiety and major depressive disorder

Elevated amygdala activity to negative faces in young adults with early onset major depressive disorder

Abnormalities in amygdala activity have been implicated in adolescents and older adults with major depressive disorder (MDD), but few studies have focused on young adults with early-onset MDD. In this study, we measured amygdala activity in 27 young adults with early-onset MDD and 25 healthy controls (HC) using functional magnetic resonance imaging (fMRI) with an emotional processing task. Both groups showed significant bilateral activation within the amygdala to threat-related facial expressions. In the matching face task, the activations of the left amygdala, thalamus, prefrontal and temporal cortex were significantly greater while the activation of the right prefrontal was significantly lower for the MDD group compared with the HC group. For the MDD group, there was a significant positive correlation between the activity of the amygdala and scores on the Chinese version of the Center for Epidemiologic Studies Depression Scale. Overall, our findings suggest that young adults with early-onset MDD may be characterized by abnormalities in nodes along the fronto-limbic pathways when facing threat-related facial expression.

Common and distinct neural correlates of emotional processing in Bipolar Disorder and Major Depressive Disorder: a voxel-based meta-analysis of functional magnetic resonance imaging studies

Neuroimaging studies have consistently shown functional brain abnormalities in patients with Bipolar Disorder (BD) and Major Depressive Disorder (MDD). However, the extent to which these two disorders are associated with similar or distinct neural changes remains unclear. We conducted a systematic review of functional magnetic resonance imaging studies comparing BD and MDD patients to healthy participants using facial affect processing paradigms. Relevant spatial coordinates from twenty original studies were subjected to quantitative Activation Likelihood Estimation meta-analyses based on 168 BD and 189 MDD patients and 344 healthy controls. We identified common and distinct patterns of neural engagement for BD and MDD within the facial affect processing network. Both disorders were associated with increased engagement of limbic regions. Diagnosis-specific differences were observed in cortical, thalamic and striatal regions. Decreased ventrolateral prefrontal cortical engagement was associated with BD while relative hypoactivation of the sensorimotor cortices was seen in MDD. Increased responsiveness in the thalamus and basal ganglia were associated with BD. These findings were modulated by stimulus valence. These data suggest that whereas limbic overactivation is reported consistently in patients with mood disorders, future research should consider the relevance of a wider network of regions in formulating conceptual models of BD and MDD.

Cerebral responses to emotional expressions and the development of social anxiety disorder: a preliminary longitudinal study

BACKGROUND

Cross-sectional studies report biased reactivity to facial expressions among shy children, anxious adolescents, and adults with social anxiety disorder (SAD). It remains unknown whether cerebral reactivity to facial expressions can predict longitudinally the development of SAD in adolescence and characterize the degree of social anxiety among the general population of adolescents.

METHODS

In a longitudinal study of 21 general population volunteers characterized for behavioral and genetic variables, N400 event-related potentials, and 3-Tesla fMRI activations in response to happy/neutral/angry expressions were acquired at age 8-9 and 14-15, respectively.

RESULTS

By stepwise regression, N400 amplitudes acquired at age 8-9 predicted the number of DSM-IV SAD symptoms at age 14-15, with the sole, significant (P = .018) contribution of the "anger" condition. Factorial ANOVA revealed increased (Voxel-Level P((FWE)) range: .02-.0001) bilateral fMRI activations of several brain areas, including the amygdala, in response to facial expressions compared to a fixation cross. The number of symptoms of DSM-IV SAD was positively correlated with left amygdala response to angry (P((FWE)) = .036) and neutral (P((FWE)) = .025) facial expressions. Factorial ANOVA revealed that the 5-HTTLPR -S allele was associated with heightened left amygdala response to anger (P((FWE)) = .05).

CONCLUSION

Cerebral reactivity to facial expressions, anger especially, measured at different developmental stages by different techniques is associated with adolescence SAD. The 5-HTTLPR genotype affects the neural processing of interpersonal affective stimuli during development.

Recognition of scared faces and the serotonin transporter gene in young children: the Generation R Study

BACKGROUND

Previous research highlights the significance of a functional polymorphism located in the promoter region (5-HTTLPR) of the serotonin transporter gene in emotional behaviour. This study examined the effect of the 5-HTTLPR polymorphism on emotion processing in a large number of healthy preschoolers.

METHODS

The 5-HTTLPR genotype was classified in 605 children as homozygous for the short allele (SS), homozygous for the long allele (LL), or heterozygous (LS). Emotion-processing was assessed using age-appropriate computer tasks where children matched happy, sad, angry, and fearful facial expressions preceded by a shape-matching task to assess basic matching ability.

RESULTS

We found that young children could differentiate between emotion categories (F = 12.1, p < .001). The effect of 5-HTTLPR genotype depended on the emotion category presented (F = 2.3, p = .031). This effect was explained by the finding that SS children were less accurate at recognising fearful faces than LL or LS children (F = 5.3, p = .005). We did not find any significant differences as a result of 5-HTTLPR genotype for happy, sad or angry expressions (p > .05).

CONCLUSIONS

Results indicate that 5-HTTLPR allele status selectively impacts the processing of fearful but not other facial expressions. This pattern is already apparent in very young typically developing children. Results may signal an early vulnerability for affective problems before disorders emerge.

Influence of serotonin transporter genotype and catechol-O-methyltransferase Val158Met polymorphism on recognition of emotional faces

Monoamines, such as serotonin, dopamine, and norepinephrine, play a crucial role in the regulation of emotion processing and mood. In this study, we investigated how polymorphisms of the serotonin transporter (5-HTT) and catechol-O-methyltransferase (COMT) influence emotion recognition abilities. We recruited 88 female undergraduate students and assessed 5-HTT genotype and the COMT Val158Met polymorphism. The subjects completed two computerized tasks: The Penn Emotion Recognition Test (ER40) and the Penn Emotion Acuity Test (PEAT). For the ER40, we found that s-allele carriers performed significantly worse in the recognition of happy faces, but did better in the recognition of fearful faces, compared with homozygous l-carriers of the 5-HTT gene. Neither 5-HTT nor COMT genotypes influenced the ability to discriminate between different intensities of sadness or happiness on the PEAT. Moreover, there was no significant interaction between the two polymorphisms in their effect on performance on the ER40 or the PEAT.

Functional connectivity of the amygdala in early-childhood-onset depression

OBJECTIVE

Adult major depressive disorder (MDD) is associated with reduced cortico-limbic functional connectivity thought to indicate decreased top-down control of emotion. However, it is unclear whether such connectivity alterations are also present in early-childhood-onset MDD.

METHOD

A total of 51 children 7 through 11 years of age who had been prospectively studied since preschool age, completed resting state functional magnetic resonance imaging (fMRI) and were assigned to one of four groups: 1) C-MDD (N = 13), those children with a personal history of early-childhood-onset MDD; 2) M-MDD (N = 11), those with a maternal history of affective disorders; 3) CM-MDD (N = 13), those with both maternal and early-childhood-onset MDD; or 4) CON (N = 14), those without either a personal or maternal history of MDD. We used seed-based resting state functional connectivity (rsfcMRI) analysis in an independent sample of adults to identify networks showing both positive (e.g., limbic regions) and negative (e.g., dorsal frontal/parietal regions) connectivity with the amygdala. These regions were then used in region-of-interest-based analyses of our child sample.

RESULTS

We found a significant interaction between maternal affective disorder history and the child's MDD history for both positive and negative rsfcMRI networks. Specifically, when compared with CON, we found reduced connectivity between the amygdala and the "negative network" in children with C-MDD, M-MDD, and CM-MDD. Children with either C-MDD or a maternal history of MDD (but not CM-MDD) displayed reduced connectivity between the amygdala and the "positive network."

CONCLUSIONS

Our finding of an attenuated relationship between the amygdala, a region affected in MDD and involved in emotion processing, and cognitive control regions is consistent with a hypothesis of altered regulation of emotional processing in C-MDD, suggesting developmental continuity of this alteration into early childhood.

The influence of serotonin transporter polymorphisms on cortical activity: a resting EEG study

BACKGROUND

The serotonin transporter gene (5-HTT) is a key regulator of serotonergic neurotransmission and has been linked to various psychiatric disorders. Among the genetic variants, polymorphisms in the 5-HTT gene-linked polymorphic region (5-HTTLPR) and variable-number-of-tandem-repeat in the second intron (5-HTTVNTR) have functional consequences. However, their genetic impact on cortical oscillation remains unclear. This study examined the modulatory effects of 5-HTTLPR (L-allele carriers vs. non-carriers) and 5-HTTVNTR (10-repeat allele carriers vs. non-carriers) polymorphism on regional neural activity in a young female population.

METHODS

Blood samples and resting state eyes-closed electroencephalography (EEG) signals were collected from 195 healthy women and stratified into 2 sets of comparisons of 2 groups each: L-allele carriers (N=91) vs. non-carriers for 5-HTTLPR and 10-repeat allele carriers (N=25) vs. non-carriers for 5-HTTVNTR. The mean power of 18 electrodes across theta, alpha, beta, gamma, gamma1, and gamma2 frequencies was analyzed. Between-group statistics were performed by an independent t-test, and global trends of regional power were quantified by non-parametric analyses.

RESULTS

Among 5-HTTVNTR genotypes, 10-repeat allele carriers showed significantly low regional power at gamma frequencies across the brain. We noticed a consistent global trend that carriers with low transcription efficiency of 5-HTT possessed low regional powers, regardless of frequency bands. The non-parametric analyses confirmed this observation, with P values of 3.071×10-8 and 1.459×10-12 for 5-HTTLPR and 5-HTTVNTR, respectively.

CONCLUSIONS AND LIMITATIONS

Our analyses showed that genotypes with low 5-HTT activity are associated with less local neural synchronization during relaxation. The implication with respect to genetic vulnerability of 5-HTT across a broad range of psychiatric disorders is discussed. Given the low frequency of 10-repeat allele of 5-HTTVNTR in our research sample, the possibility of false positive findings should also be considered.

A new interaction between SLC6A4 variation and child abuse is associated with resting heart rate

BACKGROUND

The short form of the indel promoter polymorphism (5HTTLPR) of the serotonin transporter gene (SLC6A4) and a history of child abuse have been reported to be associated with an increased risk for the development of depression. A child abuse history has also been associated with more rapid heart rate reactions.

METHODS

A retrospective chart review identified 282 patients with major depression who had been hospitalized and genotyped for the 5HTTLPR polymorphism. A subgroup of 185 females of European ancestry was also identified and analyzed. While hospitalized, heart rate was measured. Child abuse history was documented during the diagnostic evaluation. Analyses of the relationship between 5HTTLPR genotype, history of child abuse, and admission heart rate were conducted.

RESULTS

No main effect on heart rate from the 5HTTLPR genotype or a child abuse history was demonstrated for the entire sample or the subgroup of female patients. However, a genotype-by-abuse interaction was associated with resting heart rate on admission to the hospital (P<.05). Depressed patients, who were homozygous for the long allele and who had been abused, had a heart rate on hospital admission, which was statistically higher than patients with the same genotype but who had not been abused. These findings were consistent both for the 282 patients (7.2 bpm higher) as well as for the subgroup of 185 female patients of European ancestry (9.6 bpm higher).

CONCLUSIONS

A 5HTTLPR genotype interaction of elevated heart rate with a history of child abuse was demonstrated in depressed psychiatric inpatients.

Abnormal structure or function of the amygdala is a common component of neurodevelopmental disorders

The amygdala, perhaps more than any other brain region, has been implicated in numerous neuropsychiatric and neurodevelopmental disorders. It is part of a system initially evolved to detect dangers in the environment and modulate subsequent responses, which can profoundly influence human behavior. If its threshold is set too low, normally benign aspects of the environment are perceived as dangers, interactions are limited, and anxiety may arise. If set too high, risk taking increases and inappropriate sociality may occur. Given that many neurodevelopmental disorders involve too little or too much anxiety or too little of too much social interaction, it is not surprising that the amygdala has been implicated in many of them. In this chapter, we begin by providing a brief overview of the phylogeny, ontogeny, and function of the amygdala and then appraise data from neurodevelopmental disorders which suggest amygdala dysregulation. We focus on neurodevelopmental disorders where there is evidence of amygdala dysregulation from postmortem studies, structural MRI analyses or functional MRI. However, the results are often disparate and it is not totally clear whether this is due to inherent heterogeneity or differences in methodology. Nonetheless, the amygdala is a common site for neuropathology in neurodevelopmental disorders and is therefore a potential target for therapeutics to alleviate associated symptoms.

Association between depression severity and amygdala reactivity during sad face viewing in depressed preschoolers: an fMRI study

BACKGROUND

Previous research has indicated that symptom severity and amygdala reactivity during the viewing of facial expressions of emotion are related in depression. However, it remains unclear how early in development this can be detected.

METHODS

A sample of 11 depressed preschoolers (4.5±0.8; 6 males) participated in an fMRI experiment where they viewed facial expressions of emotion. A region of interest approach was used in order to examine the relationship between amygdala activation and depression severity. Additional whole-brain analyses were conducted and the results of these analyses were examined for potential relationships with depression severity.

RESULTS

Findings indicated that depressed preschoolers exhibited a significant positive relationship between depression severity and right amygdala activity when viewing facial expressions of negative affect. In addition, we found a significant positive relationship between degree of functional activation in the occipital cortex while viewing faces and level of depression severity.

LIMITATIONS

Additional research including a larger sample of depressed preschoolers, as well as a healthy comparison group, is needed to replicate the current findings and examine their specificity at this age.

CONCLUSIONS

This is the first study directly examining brain function in depressed preschoolers. The results suggest that, similar to older children and adults with depression, amygdala responsivity and degree of depression severity are related as early as age 3.

Affective cognition and its disruption in mood disorders

In this review, we consider affective cognition, responses to emotional stimuli occurring in the context of cognitive evaluation. In particular, we discuss emotion categorization, biasing of memory and attention, as well as social/moral emotion. We discuss limited neuropsychological evidence suggesting that affective cognition depends critically on the amygdala, ventromedial frontal cortex, and the connections between them. We then consider neuroimaging studies of affective cognition in healthy volunteers, which have led to the development of more sophisticated neural models of these processes. Disturbances of affective cognition are a core and specific feature of mood disorders, and we discuss the evidence supporting this claim, both from behavioral and neuroimaging perspectives. Serotonin is considered to be a key neurotransmitter involved in depression, and there is a considerable body of research exploring whether serotonin may mediate disturbances of affective cognition. The final section presents an overview of this literature and considers implications for understanding the pathophysiology of mood disorder as well as developing and evaluating new treatment strategies.

Maternal depressive history, teen 5HTTLPR genotype, and the processing of emotional faces: Exploring mechanisms of risk

Variations in the serotonin transporter gene (5HTTLPR) and biased processing of face-emotion displays both have been implicated in the transmission of depression risk, but little is known about developmental influences on these relationships. Within a community sample of adolescents, we examine whether 5HTTLPR genotype moderates the link between maternal depressive history and errors in face-emotion labeling. When controlling for current levels of depression and anxiety among youth, a two-way interaction between maternal depressive history and 5HTTLPR genotype was detected. Specifically, adolescents whose mothers reported a depressive history and who had a low expressing genotype made more errors in classifying emotional faces when compared with adolescents with an intermediate or high expressing genotype, with or without maternal depression history. These findings highlight the complex manner in which maternal depression and genetic risk may interact to predict individual differences in social information processing.

Early impact of 5-HTTLPR polymorphism on the neural correlates of sadness

Healthy adults carrying the short (S) allele of the human serotonin transporter gene linked polymorphism (5-HTTLPR) show increased amygdala activation during visual processing of emotionally negative stimuli compared to healthy adults homozygous for the long (L) allele. To determine whether abnormal brain responses during negative emotion appear early in life in S allele carriers, functional magnetic resonance imaging (fMRI) was used to measure brain activity during a transient state of sadness in children carrying the S allele (S group) or homozygous for the L allele (L group). Blood-oxygen-level dependent (BOLD) signal changes were measured while subjects viewed blocks of neutral film excerpts and sad film excerpts. During the sad condition (relative to the neutral condition), there was significantly greater activation in the S group compared to the L group in brain regions known to be involved in normal sadness and major depression. Given that the 5-HTTLPR polymorphism has been associated with mood disorders, it is plausible that the abnormal pattern of regional brain activity detected here, in children carrying the S allele, increases susceptibility to emotional dysregulation and depressive symptoms.

Imaging-genetics applications in child psychiatry

OBJECTIVE

To place imaging-genetics research in the context of child psychiatry.

METHOD

A conceptual overview is provided, followed by discussion of specific research examples.

RESULTS

Imaging-genetics research is described linking brain function to two specific genes, for the serotonin-reuptake-transporter protein and a monoamine oxidase enzyme. Work is then described on phenotype selection in imaging genetics.

CONCLUSIONS

Child psychiatry applications of imaging genetics are only beginning to emerge. The approach holds promise for advancing understandings of pathophysiology and therapeutics.

Effects of age and MAOA genotype on the neural processing of social rejection

Adolescents are often sensitive to peer rejection, a factor that might contribute to the risk of affective disorder in this age group. Previous studies suggest a significant overlap among socioaffective brain regions involved in the response to social rejection, regions continuing to develop functionally during adolescence and regions influenced by monoamine oxidase A (MAOA) polymorphism. The current study investigated whether the neural response to social rejection is functionally immature in adolescents compared with adults, and whether these responses are modulated by MAOA genotype. Blood-oxygen-level-dependent response was measured with functional magnetic resonance imaging during a rejection-themed emotional Stroop task in 19 adolescents (aged 14-16) and 16 adults (aged 23-28) genotyped for MAOA polymorphism. Similar numbers of MAOA-L and MAOA-H carriers were recruited to maximize power to detect genotype effects. Main effects of rejection stimuli (relative to neutral and acceptance control stimuli) were seen in predicted socioaffective brain regions. Adolescents did not show the adult pattern of modulation by rejection stimuli in the right ventrolateral prefrontal cortex, suggesting continued functional maturation of this regulatory region during adolescence. Age and genotype interacted in the left amygdala, in which the predicted effect of genotype on responses to rejection stimuli was seen in the adults, but not in the adolescents. The data suggest continued functional development of the circuitry underlying the processing of social rejection between adolescence and adulthood, and show that the effects of MAOA genotype on neural responses may vary with age.

[Neurogenetics of emotional processes. Neuroimaging findings as endophenotypes for depression]

Major depression is one of the most frequent and serious psychiatric diseases. Although the disease is highly heritable, the search for candidate genes has been of limited success hitherto. The complex, polygenetic hereditary transmissions coding for heterogeneous, clinically defined phenotypes such as major depression may be better identified using the endophenotype approach. A recent study, reporting an association of the risk allele in a serotonin transporter polymorphism (5-HTTLPR) with increased amygdala responsiveness to aversive stimuli, stimulated the new research field of imaging genetics, which is characterized by the choice of neurobiological activity patterns as endophenotypes. This review discusses recent studies from this rapidly growing research field, focussing on genetic effects on cortico-limbic circuitries during emotion processing. Evidence is reviewed suggesting that potential risk-alleles for depression are associated with functional cortico-limbic abnormalities, which frequently occur in patients with major depression.

Serotonin, genetic variability, behaviour, and psychiatric disorders--a review

Brain monoamines, and serotonin in particular, have repeatedly been shown to be linked to different psychiatric conditions such as depression, anxiety, antisocial behaviour, and dependence. Many studies have implicated genetic variability in the genes encoding monoamine oxidase A (MAOA) and the serotonin transporter (5HTT) in modulating susceptibility to these conditions. Paradoxically, the risk variants of these genes have been shown, in vitro, to increase levels of serotonin, although many of the conditions are associated with decreased levels of serotonin. Furthermore, in adult humans, and monkeys with orthologous genetic polymorphisms, there is no observable correlation between these functional genetic variants and the amount or activity of the corresponding proteins in the brain. These seemingly contradictory data might be explained if the association between serotonin and these behavioural and psychiatric conditions were mainly a consequence of events taking place during foetal and neonatal brain development. In this review we explore, based on recent research, the hypothesis that the dual role of serotonin as a neurotransmitter and a neurotrophic factor has a significant impact on behaviour and risk for neuropsychiatric disorders through altered development of limbic neurocircuitry involved in emotional processing, and development of the serotonergic neurons, during early brain development.

Adolescents with major depression demonstrate increased amygdala activation

OBJECTIVE

Functional neuroimaging studies have led to a significantly deeper understanding of the underlying neural correlates and the development of several mature models of depression in adults. In contrast, our current understanding of the underlying neural substrates of adolescent depression is very limited. Although numerous studies have consistently demonstrated a hyperactive amygdala in depressed adults, the few published pediatric studies have reported opposite results in the amygdala. Thus, the main purpose of this study was to further our knowledge of the underlying neural substrates of adolescent depression by examining the bilateral amygdala specifically and the whole brain in depressed adolescents compared to healthy controls.

METHOD

Twelve unmedicated adolescents diagnosed with current major depressive disorder without a comorbid psychiatric disorder and 12 well-matched controls ages 13 to 17 years performed a facial-emotion matching task during functional magnetic resonance imaging at 3 T.

RESULTS

Region-of-interest analyses demonstrated: (1) significant bilateral amygdala activation in depressed and healthy adolescents, and (2) significantly greater left amygdala activation in depressed adolescents compared to controls. Whole-brain analysis revealed areas of significantly different brain activity in depressed adolescents compared to controls.

CONCLUSIONS

These results suggest that (1) depressed adolescents without a comorbid psychiatric disorder exhibit an abnormally hyperactive amygdala compared to healthy controls; (2) models of adult depression might be extended to include depressed adolescents; and (3) neuropsychiatric interventions that have been developed in depressed adults should be further examined in adolescents.

Volition diminishes genetically mediated amygdala hyperreactivity

Individuals carrying the short allele of a common polymorphism in the promoter region of the serotonin transporter gene (5-HTTLPR) exhibit heightened amygdala responses to passive stimulation with aversive emotional material. In turn, the level of amygdala activation in response to emotion can be decreased by will, for example by using cognitive emotion regulation strategies. In the present study, 37 female subjects (s-carriers: n=21; l/l-homozygotes: n=16) performed an emotion regulation task during functional magnetic resonance imaging to determine whether cognitive emotion regulation can modulate the genetically determined amygdala hyperreactivity in 5-HTTLPR short allele carriers. Our results demonstrate that cognitive emotion regulation diminishes the difference in amygdala reactivity to threat-related stimuli between 5-HTTLPR genotype groups. Furthermore, we also provide evidence that the effect of cognitive regulation is mediated through altered coupling between the amygdala and prefrontal regulatory regions. Our findings demonstrate that while the presence of the 5-HTTLPR short allele leads to heightened responses in the amygdala, cognitive regulation can modify genetically mediated effects upon brain function by volitionally altering prefrontal-amygdala connectivity.

Imaging phenotypes of major depressive disorder: genetic correlates

Imaging techniques are a potentially powerful method of identifying phenotypes that are associated with, or are indicative of, a vulnerability to developing major depressive disorder (MDD). Here we identify seven promising MDD-associated traits identified by magnetic resonance imaging (MRI) or positron emission tomography (PET). We evaluate whether these traits are state-independent, heritable endophenotypes, or state-dependent phenotypes that may be useful markers of treatment efficacy. In MDD, increased activity of the amygdala in response to negative stimuli appears to be a mood-congruent phenomenon, and is likely moderated by the 5-HT transporter gene (SLC6A4) promoter polymorphism (5-HTTLPR). Hippocampal volume loss is characteristic of elderly or chronically-ill samples and may be impacted by the val66met brain-derived neurotrophic factor (BDNF) gene variant and the 5-HTTLPR SLC6A4 polymorphism. White matter pathology is salient in elderly MDD cohorts but is associated with cerebrovascular disease, and is unlikely to be a useful marker of a latent MDD diathesis. Increased blood flow or metabolism of the subgenual anterior cingulate cortex (sgACC), together with gray matter volume loss in this region, is a well-replicated finding in MDD. An attenuation of the usual pattern of fronto-limbic connectivity, particularly a decreased temporal correlation in amygdala-anterior cingulate cortex (ACC) activity, is another MDD-associated trait. Concerning neuroreceptor PET imaging, decreased 5-HT(1A) binding potential in the raphe, medial temporal lobe, and medial prefrontal cortex (mPFC) has been strongly associated with MDD, and may be impacted by a functional single nucleotide polymorphism in the promoter region of the 5-HT(1A) gene (HTR1A: -1019 C/G; rs6295). Potentially indicative of inter-study variation in MDD etiology or mood state, both increased and decreased binding potential of the 5-HT transporter has been reported. Challenges facing the field include the problem of phenotypic and etiological heterogeneity, technological limitations, the confounding effects of medication, and non-disease related inter-individual variation in brain morphology and function. Further advances are likely as epigenetic, copy-number variant, gene-gene interaction, and genome-wide association (GWA) approaches are brought to bear on imaging data.

BDNF gene polymorphism (Val66Met) predicts amygdala and anterior hippocampus responses to emotional faces in anxious and depressed adolescents

A polymorphism of the human Brain Derived Neurotrophic Factor (BDNF) gene that produces a valine-to-methionine substitution at codon 66 (Val66Met) is linked to adult anxiety and mood disorders, possibly through effects on brain circuitry function. Associations between BDNF gene variants and brain activity have not been explored in anxious and depressed adolescents. The current study investigated the association between BDNF genotype and amygdala-hippocampal responses to emotional stimuli in adolescents with anxiety disorders and/or major depressive disorder (MDD) and in healthy adolescents. Twenty-seven unmedicated patients with acutely-impairing current anxiety disorders and/or MDD and 31 healthy adolescents, matched on age, gender and IQ, rated their fear of fearful, angry, neutral and happy facial expressions during collection of fMRI data on the amygdala and hippocampus. Left and right amygdala and hippocampal responses were analyzed using repeated-measures analyses of variance models, with diagnosis (patients, healthy) and genotype (Met-carriers, Val/Val homozygotes) as between-group factors and facial expression (fearful, angry, neutral, happy) as a within-subject factor. Significant effects of diagnosis and diagnosis-by-genotype interactions (F's>4, p's<0.05) characterized activations in amygdala and anterior hippocampal regions. Greater activations in patients than healthy adolescents were found. Critically, these hyperactivations were modulated by BDNF genotype: Met-carriers showed greater neural responses of emotional faces than Val/Val homozygotes in patients only. These data are first to demonstrate the contribution of BDNF gene variants to the neural correlates of adolescent anxiety and depression. Early "gene-brain" linkages may lay the foundation for longer-term patterns of neural dysfunction in affective disorders.

5-HTT genotype effect on prefrontal-amygdala coupling differs between major depression and controls

RATIONALE

In major depression, prefrontal regulation of limbic brain areas may be a key mechanism that is impaired during the processing of affective information. This prefrontal-limbic interaction has been shown to be modulated by serotonin (5-HTT) genotype, indicating a higher risk for major depressive disorder (MDD) with increasing number of 5-HTT low-expression alleles.

OBJECTIVE

Functional magnetic resonance imaging was used to assess neural response to uncued unpleasant affective pictures in 21 unmedicated patients with MDD compared to 21 matched healthy controls, taking into account genetic influences of the 5-HTT (SCL6A4) high- and low-expression genotype.

RESULTS

Healthy controls displayed greater prefrontal activation (BA10) to uncued negative pictures compared to patients with MDD. While in healthy controls prefrontal (BA10) activation and BA10-amygdala coupling increased with the number of 5-HTT low-expression risk alleles, this effect was abolished, and even reversed, in patients with MDD. In MDD, connectivity decreased with severity of depressive symptoms (HAMD total score).

CONCLUSION

These findings suggest that increased medial prefrontal (BA10) activation and BA10-amygdala connectivity may counteract the risk for MDD in healthy carriers of 5-HTT low-expression alleles, while this protective factor might be lost in patients who actually suffer from MDD. Prefrontal-limbic regulation in risk populations could be a target of early interventions and should be the focus of further research.

Common and distinct amygdala-function perturbations in depressed vs anxious adolescents

CONTEXT

Few studies directly compare amygdala function in depressive and anxiety disorders. Data from longitudinal research emphasize the need for such studies in adolescents.

OBJECTIVE

To compare amygdala response to varying attention and emotion conditions among adolescents with major depressive disorder (MDD) or anxiety disorders, relative to adolescents with no psychopathology.

DESIGN

Case-control study.

SETTING

Government clinical research institute.

PARTICIPANTS

Eighty-seven adolescents matched on age, sex, intelligence, and social class: 26 with MDD (14 with and 12 without anxiety disorders), 16 with anxiety disorders but no depression, and 45 without psychopathology.

MAIN OUTCOME MEASURES

Blood oxygen level-dependent signal in the amygdala, measured by means of event-related functional magnetic resonance imaging. During imaging, participants viewed facial expressions (neutral, fearful, angry, and happy) while attention was constrained (afraid, hostility, and nose-width ratings) or unconstrained (passive viewing).

RESULTS

Left and right amygdala activation differed as a function of diagnosis, facial expression, and attention condition both when patients with comorbid MDD and anxiety were included and when they were excluded (group x emotion x attention interactions, P < or = .03). Focusing on fearful face-viewing events, patients with anxiety and those with MDD both differed in amygdala responses from healthy participants and from each other during passive viewing. However, both MDD and anxiety groups, relative to healthy participants, exhibited similar signs of amygdala hyperactivation to fearful faces when subjectively experienced fear was rated.

CONCLUSIONS

Adolescent MDD and anxiety disorders exhibit common and distinct functional neural correlates during face processing. Attention modulates the degree to which common or distinct amygdala perturbations manifest in these patient groups, relative to healthy peers.