Serotonin transporter gene moderates associations between mood, memory and hippocampal volume

Systematic review reveals multiple sexually antagonistic polymorphisms affecting human disease and complex traits

An evolutionary model for sex differences in disease risk posits that alleles conferring higher risk in one sex may be protective in the other. These sexually antagonistic (SA) alleles are predicted to be maintained at frequencies higher than expected under purifying selection against unconditionally deleterious alleles, but there are apparently no examples in humans. Discipline-specific terminology, rather than a genuine lack of such alleles, could explain this disparity. We undertook a two-stage review of evidence for SA polymorphisms in humans using search terms from (i) evolutionary biology and (ii) biomedicine. Although the first stage returned no eligible studies, the second revealed 51 genes with sex-opposite effects; 22 increased disease risk or severity in one sex but protected the other. Those with net positive effects occurred at higher frequencies. None were referred to as SA. Our review reveals significant communication barriers to fields as a result of discipline-specific terminology.

Sexual risk-taking and subcortical brain volume in adolescence

Background

The developmental period of adolescence marks the initiation of new socioemotional and physical behaviors, including sexual intercourse. However, little is known about neurodevelopmental influences on adolescent sexual decision-making.

Purpose

We sought to determine how subcortical brain volume correlated with condom use, and whether those associations differed by gender and pubertal development.

Methods

We used FreeSurfer to extract subcortical volume among N = 169 sexually experienced youth (mean age 16.07 years; 31.95% female). We conducted multiple linear regressions to examine the relationship between frequency of condom use and subcortical volume, and whether these associations would be moderated by gender and pubertal development.

Results

We found that the relationship between brain volume and condom use was better accounted for by pubertal development than by gender, and moderated the association between limbic brain volume and condom use. No significant relationships were observed in reward areas (e.g., nucleus accumbens) or prefrontal cortical control areas.

Conclusions

These data highlight the potential relevance of subcortical socioemotional processing structures in adolescents' sexual decision-making.

Alterations in serotonin transporter and body image-related cognition in anorexia nervosa

The serotonin system has been implicated in the pathophysiology of anorexia nervosa (AN). A recent report proposed that body image distortion (BID), a core symptom of AN, may relate to abnormalities of the serotonin system, especially the serotonin transporter (5HTT). Positron emission tomography (PET) studies of underweight patients with active AN reported alterations in serotonin receptors, but not 5HTT. Here, we aimed to disclose the clinicopathophysiology of AN by focusing on 5HTT and cognitive functions, including BID, in groups with active AN. Twenty-two underweight female patients with AN (12 restricting-type AN (ANR); 10 binge-eating/purging-type AN (ANBP)) and 20 age-matched healthy female subjects underwent PET with a 5HTT radioligand [¹¹C]DASB. The binding potential (BP_ND) of [¹¹C]DASB was estimated semiquantitatively, and clinical data from Raven's colored progressive matrices for general intelligence, the Stroop test for focused attention, the Iowa gambling task for decision making and a dot-probe task designed for BID were compared with the levels of BP_ND in different groups. [¹¹C]DASB BP_ND was significantly decreased in the medial parietal cortex in patients with AN and in the dorsal raphe in patients with ANR compared with healthy subjects (p < .05 corrected). Patients with ANR showed a significantly negative correlation between [¹¹C]DASB BP_ND in the dorsal raphe and performance on the dot-probe task (p < .05 corrected). While reduced 5HTT in the medial parietal cortex (the somatosensory association area) is pathophysiologically important in AN in general, additional 5HTT reduction in the dorsal raphe as seen in ANR is implicated for the clinicopathophysiological relevance.

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5HTT decreased in the parietal cortex in patients with AN.

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5HTT decreased in the parietal cortex in patients with ANBP.

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5HTT decreased in the parietal cortex and the dorsal raphe in patients with ANR.

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Patients with AN were poor at responding to the test for body image distortion (BID).

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5HTT in the dorsal raphe was associated with cognitive performance of BID.

Gender Moderates Chronic Nicotine Cigarette Effects on Verbal Memory in Young Adults

Background: Rates of nicotine use remain a prominent public health concern, especially among young adults. Previous findings have demonstrated that chronic exposure to nicotine during adolescence may be linked to various neurocognitive deficits. Nicotine differentially affects the brain by gender. Objectives: The present study investigated the effects of gender and chronic nicotine use on cognition in the developing brain. Methods: From 2008 to 2011, 57 young adult (ages 18-25) participants were recruited as part of a larger cross-sectional neuroimaging study and divided into 21 nicotine users (12 female) and 36 non-using controls (17 female). Participants completed various questionnaires, drug use interview, neuropsychological battery, and MRI scan in a university setting. A series of multiple regressions was conducted with nicotine group and gender*nicotine group interaction as predictors. Results: After controlling for gender, nicotine group status alone was not associated with neuropsychological performance. A gender x nicotine interaction was significantly associated with performance on trial 1, short delay free recall, and long delay free recall of the CVLT-II. Female smokers demonstrated better performance on trial 1 and short and long delay free recall than female controls. Male smokers performed more poorly than male controls on short and long delay free recall. Conclusions: These preliminary findings suggest that cognitive effects of chronic nicotine use are moderated by gender. Further research is needed to determine causality, and identify underlying brain structures and function that may be responsible for differences in verbal memory.

Depression related cerebral pathology and its relationship with cognitive functioning: A systematic review

BACKGROUND

Depression's relationship with cerebral abnormalities and cognitive decline is temporally dynamic. Despite clear clinical utility, understanding depression's effect on cerebral structures, cognitive impairment and the interaction between these symptoms has had limited consideration.

METHODS

This review summarised studies examining a clinical depression diagnosis or validated scales measuring depressive symptoms, data concerning amyloid-beta (Aβ) levels, brain structure and function focusing on hippocampal alterations, or white matter hyperintensities (WMH), and at least one validated neuropsychological test. Online database searches of: PsycINFO, EMBASE, MEDLINE, and Scopus were conducted to identify potential articles.

RESULTS

While depression was consistently associated with cross-sectionally cognitive decline across multiple domains, the neuropathological basis of this dysfunction remained unclear. Hippocampal, frontal, and limbic dysfunction as well as cortical thinning, WMH, and Aβ burden all provide inconsistent findings, likely due to depression subtypes. The consistency of these findings additionally decreases when examining this relationship longitudinally, as these results are further confounded by pre-dementia states. The therapeutic interventions examined were more efficacious in the younger compared with the older samples, who were characterised by greater WMH and Aβ burden.

LIMITATIONS

The limited number of longitudinal and interventional studies in addition to the heterogeneity of the samples restricts their generalisability.

CONCLUSIONS

Symptomatological differences between early-onset and late-onset depression (EOD and LOD) appear crucial in understanding whether late-life depression is the primary or secondary source of cerebral pathology. Though severe cognitive impairments and clearer neuropathological underpinnings are more characteristic of LOD than EOD, the inconsistency of valid biomarkers remains problematic.

Interactive effects of genetic polymorphisms and childhood adversity on brain morphologic changes in depression

The etiology of depression is characterized by the interplay of genetic and environmental factors and brain structural alteration. Childhood adversity is a major contributing factor in the development of depression. Interactions between childhood adversity and candidate genes for depression could affect brain morphology via the modulation of neurotrophic factors, serotonergic neurotransmission, or the hypothalamus-pituitary-adrenal (HPA) axis, and this pathway may explain the subsequent onset of depression. Childhood adversity is associated with structural changes in the hippocampus, amygdala, anterior cingulate cortex (ACC), and prefrontal cortex (PFC), as well as white matter tracts such as the corpus callosum, cingulum, and uncinate fasciculus. Childhood adversity showed an interaction with the brain-derived neurotrophic factor (BDNF) gene Val66Met polymorphism, serotonin transporter-linked promoter region (5-HTTLPR), and FK506 binding protein 51 (FKBP5) gene rs1360780 in brain morphologic changes in patients with depression and in a non-clinical population. Individuals with the Met allele of BDNF Val66Met and a history of childhood adversity had reduced volume in the hippocampus and its subfields, amygdala, and PFC and thinner rostral ACC in a study of depressed patients and healthy controls. The S allele of 5-HTTLPR combined with exposure to childhood adversity or a poorer parenting environment was associated with a smaller hippocampal volume and subsequent onset of depression. The FKBP5 gene rs160780 had a significant interaction with childhood adversity in the white matter integrity of brain regions involved in emotion processing. This review identified that imaging genetic studies on childhood adversity may deepen our understanding on the neurobiological background of depression by scrutinizing complicated pathways of genetic factors, early psychosocial environments, and the accompanying morphologic changes in emotion-processing neural circuitry.

Genetic influence alters the brain synchronism in perception and timing

Background

Studies at the molecular level aim to integrate genetic and neurobiological data to provide an increasingly detailed understanding of phenotypes related to the ability in time perception.

Main Text

This study suggests that the polymorphisms genetic SLC6A4 5-HTTLPR, 5HTR2A T102C, DRD2/ANKK1-Taq1A, SLC6A3 3’-UTR VNTR, COMT Val158Met, CLOCK genes and GABRB2 A/C as modification factor at neurochemical levels associated with several neurofunctional aspects, modifying the circadian rhythm and built-in cognitive functions in the timing. We conducted a literature review with 102 studies that met inclusion criteria to synthesize findings on genetic polymorphisms and their influence on the timing.

Conclusion

The findings suggest an association of genetic polymorphisms on behavioral aspects related in timing. However, order to confirm the paradigm of association in the timing as a function of the molecular level, still need to be addressed future research.

Situation Awareness Performance in Healthy Young Adults Is Associated With a Serotonin Transporter Gene Polymorphism

Background Situation awareness (SA) is defined in three levels: SA1 is the perception of the elements in a specific context, SA2 is the comprehension of their meaning, and SA3 is the projection of their status. Purpose To analyze the possible association of a genetic polymorphism in the serotonin transporter ( SLC6A4) gene and performance on the Situational Awareness test (SAtest). Methods SAtest was applied to a sample of 230 healthy Colombian subjects, using the Psychology Experiment Building Language platform and a functional polymorphism in the SLC6A4 gene was genotyped by polymerase chain reaction. Results In the SA1 level, s/s genotype carriers had worse accuracy, in comparison with s/l and l/l genotypes. At SA2 level, l/l genotype carriers had better accuracy than s/s and s/l individuals and that in the SA3 level, l/l carriers also had better accuracy. These associations were significant after correction for multiple testing. Conclusions It is possible that l/l carriers have a better ability to perceive and focus their attention on the elements of their environment and to have the capacity to understand and predict what will happen with those elements. This is the first genetic study of SA performance in healthy participants. Additional investigations of other genes could contribute to the understanding of the molecular correlates of SA in healthy subjects and in neuropsychiatric patients.

IL-18 Serum Levels and Variants of the Serotonin Transporter Gene Are Related to Awareness of Emotions in Healthy Subjects: A Preliminary Study

OBJECTIVE

Interaction between the nervous and immune systems may influence emotions, ultimately affecting human health. Cytokines may play a role in developing emotional dysregulation as in alexithymia, a personality construct characterized by the subclinical inability to identify and describe emotions, often associated with several psychiatric and psychosomatic disorders. The proinflammatory cytokine IL-18, with a recognized role in brain functions, may influence serotonin metabolism and appears to be associated with alexithymia. Healthy individuals carrying the long allele (L) of the serotonin transporter gene polymorphic region (5-HTTLPR), and thus having lower concentrations of serotonin in the synaptic cleft, show a greater tendency toward alexithymia, with some gender differences. To explore a potential physiological interaction between IL-18, serotonin neurotransmission, and alexithymia, we investigated whether IL-18 serum levels and 5-HTTLPR are linked to alexithymic traits in healthy subjects.

METHODS

We measured IL-18 serum levels in 115 Italian-Caucasian healthy subjects genotyped for 5-HTTLPR allele variants, divided by gender and assessed for alexithymia scores using the 20-item Toronto Alexithymia Scale.

RESULTS

IL-18 levels are significantly more elevated in individuals with the LL genotype (n = 25) than in carriers of the short allele (n = 90, p = 0.0073). Specifically, in LL males (n = 11), i.e., the group with the most relevant increase in IL-18, cytokine values positively correlated with difficulty identifying feelings, which is a component of alexithymia (r = 0.634, p = 0.036).

CONCLUSIONS

These results indicate a possible novel interaction between IL-18 and the serotoninergic system to mediate emotional unawareness, suggesting putative biological predictors of emotional dysregulation, which in turn can act as a risk factor for a variety of medical conditions in susceptible subjects.

Sex differences modulating serotonergic polymorphisms implicated in the mechanistic pathways of risk for depression and related disorders

Despite consistent observations of sex differences in depression and related emotional disorders, we do not yet know how these sex differences modulate the effects of genetic polymorphisms implicated in risk for these disorders. This Mini-Review focuses on genetic polymorphisms of the serotonergic system to illustrate how sex differences might modulate the neurobiological pathways involved in the development of depression. We consider the interacting role of environmental factors such as early-life stress. Given limited current knowledge about this topic, we highlight methodological considerations, challenges, and guidelines for future research. © 2016 Wiley Periodicals, Inc.

Hippocampal volume as an amplifier of the effect of social context on adolescent depression

Recent models have focused on how brain-based individual differences in social sensitivity shape affective development in adolescence, when rates of depression escalate. Given the importance of the hippocampus in binding contextual and affective elements of experience, as well as its putative role in depression, we examined hippocampal volume as a moderator of the effects of social context on depressive symptoms in a sample of 209 Mexican-origin adolescents. Adolescents with larger versus smaller hippocampal volumes showed heightened sensitivity in their depressive symptoms to a protective factor inside the home (sense of family connectedness) and a risk factor outside of it (community crime exposure). These interactive effects uniquely predicted depressive symptoms and were greater for the left side, suggesting two independent social-contextual contributions to depression that were moderated by left hippocampal volume. Results elucidate complex brain-environment interplay in adolescent depression, offering clues about for whom and how social context plays a role.

Imaging genetics in neurodevelopmental psychopathology

Neurodevelopmental disorders are defined by highly heritable problems during development and brain growth. Attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorders (ASDs), and intellectual disability (ID) are frequent neurodevelopmental disorders, with common comorbidity among them. Imaging genetics studies on the role of disease-linked genetic variants on brain structure and function have been performed to unravel the etiology of these disorders. Here, we reviewed imaging genetics literature on these disorders attempting to understand the mechanisms of individual disorders and their clinical overlap. For ADHD and ASD, we selected replicated candidate genes implicated through common genetic variants. For ID, which is mainly caused by rare variants, we included genes for relatively frequent forms of ID occurring comorbid with ADHD or ASD. We reviewed case-control studies and studies of risk variants in healthy individuals. Imaging genetics studies for ADHD were retrieved for SLC6A3/DAT1, DRD2, DRD4, NOS1, and SLC6A4/5HTT. For ASD, studies on CNTNAP2, MET, OXTR, and SLC6A4/5HTT were found. For ID, we reviewed the genes FMR1, TSC1 and TSC2, NF1, and MECP2. Alterations in brain volume, activity, and connectivity were observed. Several findings were consistent across studies, implicating, for example, SLC6A4/5HTT in brain activation and functional connectivity related to emotion regulation. However, many studies had small sample sizes, and hypothesis-based, brain region-specific studies were common. Results from available studies confirm that imaging genetics can provide insight into the link between genes, disease-related behavior, and the brain. However, the field is still in its early stages, and conclusions about shared mechanisms cannot yet be drawn.

Association between the serotonin transporter gene polymorphism and verbal learning in older adults is moderated by gender

The S allele of the functional 5-HTTLPR polymorphism has previously been associated with reductions in memory function. Given the change in function of the serotonergic system in older adults, and the functional consequences of memory decline in this age group, further investigation into the impact of 5-HTTLPR in healthy older adults is required. This investigation examined the effect of 5-HTTLPR variants (S carriers versus L/L homozygotes) on verbal and visual episodic memory in 438 healthy older adults participating in the Tasmanian Healthy Brain Project (age range 50-79 years, M=60.35, s.d.=6.75). Direct effects of 5-HTTLPR on memory processes, in addition to indirect effects through interaction with age and gender, were assessed. Although no direct effects of 5-HTTLPR on memory processes were identified, our results indicated that gender significantly moderated the impact that 5-HTTLPR variants exerted on the relationship between age and verbal episodic memory function as assessed by the Rey Auditory Verbal Learning Test. No significant direct or indirect effects were identified in relation to visual memory performance. Overall, this investigation found evidence to suggest that 5-HTTLPR genotype affects the association of age and verbal episodic memory for males and females differently, with the predicted negative effect of S carriage present in males but not females. Such findings indicate a gender-dependent role for 5-HTTLPR in the verbal episodic memory system of healthy older adults.

A pilot study on predictors of brainstem raphe abnormality in patients with major depressive disorder

BACKGROUND

Hypo/anechogenicity of the brainstem raphe (BR) structures has been suggested as a possible transcranial parenchymal sonography (TCS) marker associated with depression.

AIM

The aim of this study was to analyze possible association of the abnormal BR echogenicity in patients with major depression when compared to healthy controls, and to evaluate its clinical and genetic correlates.

METHODS

TCS was performed in 53 patients diagnosed as major depressive disorder (MDD) without psychotic symptoms and in 54 healthy matched controls.

RESULTS

The TCS detected BR abnormalities were significantly more frequent in MDD patients (35 out of 53; 66%) in comparison to matched controls (5 out of 56; 9%). The prevalence of short allele (s) homozygocity in the length polymorphism of the promoter region of the serotonin transporter gene (5-HTTLPR) was significantly higher in MDD patients relative to those with normal BR echogenicity. A stepwise statistical discriminant analysis revealed statistically significant separation between MDD patients with and without BR abnormalities groups based on the four predictors combined: the Hamilton Anxiety Rating Scale item 5 ("difficulty in concentration, poor memory"), presence of social phobia, s allele homozygocity of the 5-HTTLPR polymorphism, and presence of generalized anxiety disorder.

LIMITATIONS

Cross-sectional design and heterogenous treatment of depressed patients.

CONCLUSIONS

Reduced BR echogenicity in at least a subgroup of MDD patients may reflect a particular phenotype, characterized by more prevalent comorbid anxiety disorders, associated with particular genetic polymorphisms and neurotransmitter(s) deficits, most probably altered serotonergic mechanisms.

Neurobiology of Anorexia Nervosa: Serotonin Dysfunctions Link Self-Starvation with Body Image Disturbances through an Impaired Body Memory

The etiology of anorexia nervosa (AN) is still unclear, despite that it is a critical and potentially mortal illness. A recent neurobiological model considers AN as the outcome of dysfunctions in the neuronal processes related to appetite and emotionality (Kaye et al., 2009, 2013). However, this model still is not able to answer a critical question: What is behind body image disturbances (BIDs) in AN? The article starts its analysis from reviewing some of the studies exploring the effects of the serotonin systems in memory (episodic, working, and spatial) and its dysfunctions. The review suggests that serotonin disturbances may: (a) facilitate the encoding of third person (allocentric) episodic memories; (b) facilitate the consolidation of emotional episodic memories (e.g., teasing), if preceded by repeated stress; (c) reduce voluntary inhibition of mnestic contents; (d) impair allocentric spatial memory. If we discuss these results within the interpretative frame suggested by the “Allocentric Lock Hypothesis” (Riva, 2012, 2014), we can hypothesize that altered serotoninergic activity in AN patients: (i) improves their ability to store and consolidate negative autobiographical memories, including those of their body, in allocentric perspective; (ii) impairs their ability to trigger voluntary inhibition of the previously stored negative memory of the body; (iii) impairs their capacity to retrieve/update allocentric information. Taken together, these points suggest a possible link between serotonin dysfunctions, memory impairments and BIDs: the impossibility of updating a disturbed body memory using real time experiential data—I'm locked to a wrong body stored in long term memory—pushes AN patients to control body weight and shape even when underweight.

Sex differences in MDMA-induced toxicity in Sprague-Dawley rats

Recent evidence demonstrates that female subjects show exaggerated responses to 3,4-methylenedioxymethamphetamine (MDMA) compared with males. The aim of our study was to evaluate sex differences and the role of endogenous gonadal hormones on the effects of MDMA. Fifty-six intact and gonadectomized male and female Sprague-Dawley rats were randomly assigned to either MDMA (5 mg/kg) or saline treatment. Learning and memory were assessed using the Morris water maze (MWM). The expression of Bax and Bcl-2 in the hippocampus was detected by Western blotting. Behavioral analysis showed that MDMA led to memory impairment in both male and female rats. The female rats showed more sensitivity to impairment than the males, as assessed using all the memory parameters in the MWM. Ovariectomy attenuated the MDMA-induced memory impairment. By contrast, orchiectomized rats showed more impairment than MDMA-treated intact male rats. Bcl-2 and Bax were down-regulated and up-regulated in MDMA-treated male and female rats, respectively. MDMA treatment in the orchiectomized rats led to upregulation of Bax and down-regulation of Bcl-2. Ovariectomy attenuated the MDMA-induced up-regulation of Bax and caused more expression of Bcl-2 compared with what was observed in the MDMA-treated intact female rats. In summary, female rats showed exaggerated responses to the effects of MDMA and this may be explained by endogenous gonadal hormones.

Developmentally Sensitive Interaction Effects of Genes and the Social Environment on Total and Subcortical Brain Volumes

Smaller total brain and subcortical volumes have been linked to psychopathology including attention-deficit/hyperactivity disorder (ADHD). Identifying mechanisms underlying these alterations, therefore, is of great importance. We investigated the role of gene-environment interactions (GxE) in interindividual variability of total gray matter (GM), caudate, and putamen volumes. Brain volumes were derived from structural magnetic resonance imaging scans in participants with (N = 312) and without ADHD (N = 437) from N = 402 families (age M = 17.00, SD = 3.60). GxE effects between DAT1, 5-HTT, and DRD4 and social environments (maternal expressed warmth and criticism; positive and deviant peer affiliation) as well as the possible moderating effect of age were examined using linear mixed modeling. We also tested whether findings depended on ADHD severity. Deviant peer affiliation was associated with lower caudate volume. Participants with low deviant peer affiliations had larger total GM volumes with increasing age. Likewise, developmentally sensitive GxE effects were found on total GM and putamen volume. For total GM, differential age effects were found for DAT1 9-repeat and HTTLPR L/L genotypes, depending on the amount of positive peer affiliation. For putamen volume, DRD4 7-repeat carriers and DAT1 10/10 homozygotes showed opposite age relations depending on positive peer affiliation and maternal criticism, respectively. All results were independent of ADHD severity. The presence of differential age-dependent GxE effects might explain the diverse and sometimes opposing results of environmental and genetic effects on brain volumes observed so far.

The influence of 5-HTTLPR and Val66Met polymorphisms on cortical thickness and volume in limbic and paralimbic regions in depression: a preliminary study

BACKGROUND

Structural brain abnormalities have been investigated in multi-genetic and complex disorders such as major depressive disorder (MDD). Among the various candidate genes implicated in MDD, the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism and 5-HT transporter gene linked polymorphism (5-HTTLPR) have garnered the most attention due to their putative roles in neural plasticity and antidepressant response. However, relatively few studies have assessed the influence of these polymorphysims on cortical thickness or brain volume in para-limbic and limbic regions in MDD, which was the aim of this study.

METHODS

Forty-three adults with MDD and 15 healthy controls (HC) underwent structural magnetic resonance imaging (MRI). Cortical thickness was assessed in frontal, cingulate and temporal regions. Volumetric measures were carried out in the thalamus, caudate, putamen, pallidum, hippocampus and amygdala. Participants were genotyped to determine their 5-HTTLPR (tri-allelic) and Val66Met polymorphisms.

RESULTS

In the combined sample (MDD + HC), smaller right pallidum volumes were found in LA/S (LA/S & LA/LG) heterozygotes compared to S/S (S/S, LG/S & LG/LG) homozygotes, though the effect was modest. In the MDD group, larger left thalamus and putamen volumes were observed in LA/LA homozygotes. No Val66Met or 5-HTTLPR genotype effects existed on cortical thickness and no main effects of the Val66Met polymorphism were observed.

CONCLUSION

Our preliminary results suggest that the 5-HTTLPR polymorphism is associated with morphometric changes in regions known to play an important role in emotional and reward processing in depression. A larger sample size is required to replicate these findings and to potentially reveal subtle morphometric changes.

Imaging genetics studies on monoaminergic genes in major depressive disorder

Although depression is the leading cause of disability worldwide, current understanding of the neurobiology of depression has failed to be translated into clinical practice. Major depressive disorder (MDD) pathogenesis is considered to be significantly influenced by multiple risk genes, however genetic effects are not simply expressed at a behavioral level. Therefore the concept of endophenotype has been applied in psychiatric genetics. Imaging genetics applies anatomical or functional imaging technologies as phenotypic assays to evaluate genetic variation and their impact on behavior. This paper attempts to provide a comprehensive review of available imaging genetics studies, including reports on genetic variants that have most frequently been linked to MDD, such as the monoaminergic genes (serotonin transporter gene, monoamine oxidase A gene, tryptophan hydroxylase-2 gene, serotonin receptor 1A gene and catechol-O-methyl transferase gene), with regard to key structures involved in emotion processing, such as the hippocampus, amygdala, anterior cingulate cortex and orbitofrontal cortex.

Effects of marijuana use on prefrontal and parietal volumes and cognition in emerging adults

RATIONALE

Chronic marijuana (MJ) use among adolescents has been associated with structural and functional abnormalities, particularly in developing regions responsible for higher order cognition.

OBJECTIVES

This study investigated prefrontal (PFC) and parietal volumes and executive function in emerging adult MJ users and explored potential gender differences.

METHODS

Participants (ages 18-25) were 27 MJ users and 32 controls without neurologic or psychiatric disorders or heavy other drug use. A series of multiple regressions examined whether group status, past year MJ use, and their interactions with gender predicted ROI volumes. Post hoc analyses consisted of brain-behavior correlations between volumes and cognitive variables and Fisher's z tests to assess group differences.

RESULTS

MJ users demonstrated significantly smaller medial orbitofrontal (mOFC; p = 0.004, FDR p = 0.024) and inferior parietal volumes (p = 0.04, FDR p = 0.12); follow-up regressions found that increased past year MJ use did not significantly dose-dependently predict smaller mOFC volume in a sub-sample of individuals with at least one past year MJ use. There were no significant gender interactions. There was a significant brain-behavior difference by group, such that smaller mOFC volumes were associated with poorer complex attention for MJ users (p < 0.05).

CONCLUSIONS

Smaller mOFC volumes among MJ users suggest disruption of typical neurodevelopmental processes associated with regular MJ use for both genders. These results highlight the need for longitudinal, multi-modal imaging studies providing clearer information on timing of neurodevelopmental processes and neurocognitive impacts of youth MJ initiation.

5-HTTLPR Genotype Moderates the Effects of Past Ecstasy Use on Verbal Memory Performance in Adolescent and Emerging Adults: A Pilot Study

OBJECTIVE

Ecstasy use is associated with memory deficits. Serotonin transporter gene (5-HTTLPR) polymorphisms have been linked with memory function in healthy samples. The present pilot study investigated the influence of 5-HTTLPR polymorphisms on memory performance in ecstasy users, marijuana-using controls, and non-drug-using controls, after a minimum of 7 days of abstinence.

METHOD

Data were collected from 116 young adults (18-25 years-old), including 45 controls, 42 marijuana users, and 29 ecstasy users, and were balanced for 5-HTTLPR genotype. Participants were abstinent seven days prior to completing memory testing. Three MANCOVAs and one ANCOVA were run to examine whether drug group, 5-HTTLPR genotype, and their interactions predicted verbal and visual memory after controlling for gender, past year alcohol use, other drug use, and nicotine cotinine levels.

RESULTS

MANCOVA and ANCOVA analysis revealed a significant interaction between drug group and genotype (p = .03) such that ecstasy users with the L/L genotype performed significantly worse on CVLT-2 total recall (p = .05), short (p = .008) and long delay free recall (p = .01), and recognition (p = .006), with the reverse pattern found in controls. Ecstasy did not significantly predict visual memory. 5-HTTLPR genotype significantly predicted memory for faces (p = .02); short allele carriers performed better than those with L/L genotype.

CONCLUSIONS

5-HTTLPR genotype moderated the effects of ecstasy on verbal memory, with L/L carriers performing worse compared to controls. Future research should continue to examine individual differences in ecstasy's impact on neurocognitive performance as well as relationships with neuronal structure. Additional screening and prevention efforts focused on adolescents and emerging adults are necessary to prevent ecstasy consumption.

SERT and NET polymorphisms, temperament and antidepressant response

BACKGROUND

The genetic variations in norepinephrine transporter (NET) and serotonin transporter (SERT) genes have been associated with personality traits, several psychiatric disorders and the efficacy of antidepressant treatment.

AIMS

We investigated the separate effects and possible interactions between NET T-182C (rs2242446) and SERT 5-HTTLPR (rs4795541) polymorphisms on selective serotonin reuptake inhibitors (SSRI) treatment response and temperamental traits assessed by the Temperament and Character Inventory (TCI) in a clinical sample of subjects with major depressive disorder (MDD).

METHODS

Our sample of 97 patients with major depression completed the 107-item TCI temperament questionnaire (version IX) at the initial assessment of the study and after 6 weeks of follow-up. All subjects received selective SSRI medications. Temperament dimension scores at baseline ( 1 ) and endpoint ( 2 ) during antidepressant treatment were analyzed between NET and SERT genotypes.

RESULTS

SS-genotype of 5-HTTLPR was associated with higher baseline Persistence scores than SL- or LL-genotype. A corresponding but weaker association was found at endpoint. No differences were found between 5-HTTLPR genotypes and other temperament dimensions and 5-HTTLPR genotypes had no effect on treatment response.

CONCLUSIONS

Our results suggest that the SS-genotype of 5-HTTLPR is associated with Persistence scores in patients with MDD. Higher Persistence could be viewed as a negative trait when recovering from stress and its association with short and "weaker" S-allele may be related to less efficient serotonin neurotransmission, possibly resulting in less effective coping strategies on a behavioral level.

Influences of COMT and 5-HTTLPR polymorphisms on cognitive flexibility in healthy women: inhibition of prepotent responses and memory updating

Understanding genetic factors that affect monoamine neurotransmitters flux in prefrontal cortex may help to further specify the complex neurobiological processes that underlie cognitive function and dysfunction in health and illness. The current study examined the associations between the polymorphisms of dopaminergic (COMT Met158Val) and serotoninergic (5-HTTLPR) genes and the sequential pattern of responses in a motor random generation task providing well-established indexes for executive functioning in a large sample of 255 healthy women. Participants homozygous for the Met allele of the COMT polymorphism showed impaired inhibition of prepotent responses, whereas individuals homozygous for the s-allele of the 5-HTTLPR showed a restricted ability to update information in working memory. Taken together the results indicate differentiated influences of dopaminergic and serotonergic genes on important and definite executive sub-processes related to cognitive flexibility.

Effects of the serotonin transporter polymorphism and history of major depression on overgeneral autobiographical memory

Overgeneral autobiographical memory (OGM) is a key memory deficit in major depressive disorder (MDD). Much research has examined cognitive mechanisms underlying OGM, but little work has investigated potential neurobiological influences. There is preliminary evidence that a genetic serotonergic vulnerability coupled with depressive symptoms may be associated with other memory impairments, and experimental research suggests a role for serotonin in OGM. We investigated whether a polymorphism in the promoter region of the serotonin transporter gene (5-HTTLPR) was associated with OGM in interaction with a lifetime history of MDD in 370 young adults in a longitudinal study of risk for emotional disorders. There was a significant interaction between 5-HTTLPR genotype and lifetime history of MDD in predicting OGM. Among S allele homozygotes, MDD history was associated with greater OGM, whereas no significant relationship between MDD history and OGM emerged among L carriers. Furthermore, there was evidence that a greater number of S alleles were associated with greater memory specificity in individuals without a history of MDD. Implications for understanding cognitive and biological risk for depression are discussed.