Transcranial Direct Current Stimulation (tDCS) for major depression - Interim analysis of cloud supervised technical data from the DepressionDC trial

BACKGROUND

Transcranial direct current stimulation (tDCS) of prefrontal cortex regions has been reported to exert antidepressant effects, though large scale multicenter trials in major depressive disorder (MDD) supporting this notion are still lacking. Application of tDCS in multicenter settings, however, requires measurement, storage and evaluation of technical parameters of tDCS sessions not only for safety reasons but also for quality control. To address this issue, we conducted an interim analysis of supervised technical data across study centers in order to monitor technical quality of tDCS in an ongoing multicenter RCT in MDD (DepressionDC trial).

METHODS

Technical data of 818 active tDCS sessions were recorded, stored in a data cloud, and analysed without violating study blinding. Impedance, voltage and current were monitored continuously with one data point recorded every second of stimulation.

RESULTS

Variability of impedance was considerable (1,42 kΩ, to 8,23 kΩ), inter-individually and even more intra-individually, but did not significantly differ between the study centre in Munich and all other sites.

CONCLUSION

Measurement, centralized data storage via data cloud and remote supervision of technical parameters of tDCS are feasible and proposed for future RCTs on therapeutic tDCS in multiple settings.

[Pharmacotherapy of anxiety disorders-Guideline-conform treatment and new developments]

Besides cognitive behavioral therapy (CBT), psychopharmacotherapy belongs to the first-line treatment approaches for anxiety disorders according to all national and international guidelines. According to studies and meta-analyses, modern antidepressants in particular have been proven to be effective. Depending on the substance, there are approvals for panic disorder, generalized anxiety disorder and social phobia. There are also approvals for other substance groups, e.g. anticonvulsants for generalized anxiety disorder. Benzodiazepines should be used with caution in view of the risk of dependency. Although effective and well-tolerated medications are available, up to 30% of patients still do not respond or do not respond adequately to treatment. Consequently, research efforts to develop new substances are important. Based on a better understanding of the complex neurobiological mechanisms underlying anxiety disorders, a large number of substances are currently undergoing clinical trials. Modulators of current and new transmitter systems, in particular the glutamatergic and the endocannabinoid systems as well as neuropeptides, are being discussed as innovative substances. Strategies are also being investigated which, in combination with psychotherapy, aim at optimizing fear extinction memory. First studies are also underway on the use of psychedelic agents in combination with psychotherapy for anxiety.

Serotonin Transporter Gene Promoter Hypomethylation as a Predictor of Antidepressant Treatment Response in Major Depression: A Replication Study

BACKGROUND

The serotonin transporter gene (SLC6A4; 5-HTT; SERT) is considered a prime candidate in pharmacogenetic research in major depressive disorder (MDD). Besides genetic variation, recent advances have spotlighted the involvement of epigenetic mechanisms such as DNA methylation in predicting antidepressant treatment response in "pharmaco-epigenetic" approaches. In MDD, lower SLC6A4 promoter methylation has been suggested to predict impaired response to serotonergic antidepressants. The present study sought to replicate and extend this finding in a large, independent sample of MDD patients.

METHODS

The sample comprised n = 236 Caucasian patients with MDD receiving antidepressant medication in a naturalistic treatment setting. Functional DNA methylation of 9 CpG sites located in the SLC6A4 promoter region was analyzed via direct sequencing of sodium bisulfite- treated DNA extracted from blood cells. Patients were assessed over the course of a 6-week in-patient treatment using the Hamilton Depression Scale (HAM-D).

RESULTS

Results confirm relative SLC6A4 hypomethylation to predict impaired antidepressant response both dimensionally and categorically (HAM-D reductions < 50%) and to furthermore be indicative of nonremission (HAM-D > 7). This also held true in a homogenous subgroup of patients continuously treated with selective serotonin reuptake inhibitors or serotonin/noradrenaline reuptake inhibitors (n = 110).

CONCLUSIONS

Impaired response to serotonergic antidepressants via SLC6A4 hypomethylation may be conveyed by increased gene expression and consequently decreased serotonin availability, which may counteract the effects of serotonergic antidepressants. The present results could in the future inform clinical decision-making towards a more personalized treatment of MDD.

Individual differences in human fear generalization-pattern identification and implications for anxiety disorders

Previous research indicates that anxiety disorders are characterized by an overgeneralization of conditioned fear as compared with healthy participants. Therefore, fear generalization is considered a key mechanism for the development of anxiety disorders. However, systematic investigations on the variance in fear generalization are lacking. Therefore, the current study aims at identifying distinctive phenotypes of fear generalization among healthy participants. To this end, 1175 participants completed a differential fear conditioning phase followed by a generalization test. To identify patterns of fear generalization, we used a k-means clustering algorithm based on individual arousal generalization gradients. Subsequently, we examined the reliability and validity of the clusters and phenotypical differences between subgroups on the basis of psychometric data and markers of fear expression. Cluster analysis reliably revealed five clusters that systematically differed in mean responses, differentiation between conditioned threat and safety, and linearity of the generalization gradients, though mean response levels accounted for most variance. Remarkably, the patterns of mean responses were already evident during fear acquisition and corresponded most closely to psychometric measures of anxiety traits. The identified clusters reliably described subgroups of healthy individuals with distinct response characteristics in a fear generalization test. Following a dimensional view of psychopathology, these clusters likely delineate risk factors for anxiety disorders. As crucial group characteristics were already evident during fear acquisition, our results emphasize the importance of average fear responses and differentiation between conditioned threat and safety as risk factors for anxiety disorders.

Effects of physical activity on cognitive performance: a controlled clinical study in depressive patients

Physical activity is a common adjunctive therapy in psychiatric and psychosomatic hospitals. In the present study, we assessed the effects of an exercise program, integrated into routine inpatient treatment, on cognitive performance and subjective severity of depression in a sample of patients suffering from major depression. We randomized n = 38 patients with unipolar depression to either physical exercise (n = 18) or occupational therapy as an active control treatment (n = 20). Both treatments were delivered in group format over a period of 3-4 weeks. Data indicate that there were significant improvements of cognitive functions and depressive symptoms in both groups, with specific treatment effects in reaction time and in short-term verbal memory favoring the physical activity group. In conclusion, we found physical exercise to be a feasible, easy-to-implement add-on therapy for depressive patients with promising effects on cognitive performance. However, these results need to be replicated in larger samples with an extended follow-up.

Is prepulse modification altered by continuous theta burst stimulation? DAT1 genotype and motor threshold interact on prepulse modification following brain stimulation

Previous studies suggest an inhibitory top-down control of the amygdala by the prefrontal cortex (PFC). Both brain regions play a role in the modulation of prepulse modification (PPM) of the acoustic startle response by a pre-stimulus. Repetitive transcranial magnetic stimulation (rTMS) can modulate the activity of the PFC and might thus affect PPM. This study tested the effect of inhibitory rTMS on PPM accounting for a genetic variant of the dopamine transporter gene (DAT1). Healthy participants (N = 102) were stimulated with continuous theta burst stimulation (cTBS, an intense form of inhibitory rTMS) or sham treatment over the right PFC. Afterwards, during continuous presentation of a background white noise a louder noise burst was presented either alone (control startle) or preceded by a prepulse. Participants were genotyped for a DAT1 variable number tandem repeat (VNTR) polymorphism. Two succeeding sessions of cTBS over the right PFC (2 × 600 stimuli with a time lag of 15 min) attenuated averaged prepulse inhibition (PPI) in participants with a high resting motor threshold. An attenuation of PPI induced by prepulses with great distances to the pulse (480, 2000 ms) was observed following active cTBS in participants that were homozygous carriers of the 10-repeat-allele of the DAT1 genotype and had a high resting motor threshold. Our results confirm the importance of the prefrontal cortex for the modulation of PPM. The effects were observed in participants with a high resting motor threshold only, probably because they received a higher dose of cTBS. The effects in homozygous carriers of the DAT1 10-repeat allele confirm the relevance of dopamine for PPM. Conducting an exploratory study we decided against the use of a correction for multiple testing.

Effects of electroconvulsive therapy on amygdala function in major depression - a longitudinal functional magnetic resonance imaging study

BACKGROUND

Electroconvulsive therapy (ECT) is one of the most effective treatments for severe depression. However, little is known regarding brain functional processes mediating ECT effects.

METHOD

In a non-randomized prospective study, functional magnetic resonance imaging data during the automatic processing of subliminally presented emotional faces were obtained twice, about 6 weeks apart, in patients with major depressive disorder (MDD) before and after treatment with ECT (ECT, n = 24). Additionally, a control sample of MDD patients treated solely with pharmacotherapy (MED, n = 23) and a healthy control sample (HC, n = 22) were obtained.

RESULTS

Before therapy, both patient groups equally showed elevated amygdala reactivity to sad faces compared with HC. After treatment, a decrease in amygdala activity to negative stimuli was discerned in both patient samples indicating a normalization of amygdala function, suggesting mechanisms potentially unspecific for ECT. Moreover, a decrease in amygdala activity to sad faces was associated with symptomatic improvements in the ECT sample (r spearman = -0.48, p = 0.044), and by tendency also for the MED sample (r spearman = -0.38, p = 0.098). However, we did not find any significant association between pre-treatment amygdala function to emotional stimuli and individual symptom improvement, neither for the ECT sample, nor for the MED sample.

CONCLUSIONS

In sum, the present study provides first results regarding functional changes in emotion processing due to ECT treatment using a longitudinal design, thus validating and extending our knowledge gained from previous treatment studies. A limitation was that ECT patients received concurrent medication treatment.

Influence of single-dose quetiapine on fear network activity - A pharmaco-imaging study

OBJECTIVE

Anxiety disorders are among the most frequent psychiatric disorders. Current treatment guidelines recommend antidepressants, the calcium modulator gabapentin, and benzodiazepines as pharmacological treatments. However, delayed onset of action precludes the use of antidepressants as an acute treatment, while benzodiazepines can be recommended only as an emergency treatment due to their inherent risk of dependence. Therefore, an alternative pharmacological agent with acute efficacy is needed. Preliminary evidence points towards possible anxiolytic properties of the atypical antipsychotic quetiapine. The goals of this study were to test the acute anxiolytic properties of quetiapine in patients suffering from arachnophobia in a challenge paradigm, and to assess the effects of quetiapine on the central nervous fear network.

METHODS

In a randomized, double-blind, placebo-controlled proof-of-concept study, n=58 arachnophobic patients underwent an fMRI scan while looking at phobia-related and neutral stimuli. Subjective anxiety was evaluated retrospectively in questionnaires.

RESULTS

The functional imaging data revealed that patients showed stronger amygdala activation to phobia-related than to neutral stimuli. However, no effect of quetiapine on fear network activity was detected. Further, on questionnaire measures, quetiapine significantly reduced somatic anxiety symptoms, but had no effect on general psychological anxiety.

CONCLUSION

Viewing phobic pictures resulted in a robust amygdala activation in arachnophobic patients. Quetiapine seems to have no influence on activation in anxiety-related brain areas but appears to reduce acute somatic anxiety symptoms in patients with specific phobia. The central nervous correlates of the anxiolytic effects of quetiapine remain to be clarified in future studies.

[Repetitive Transcranial Magnetic Stimulation (rTMS) as a Therapeutic Tool in Psychiatry - Current State of Application in Germany]

The repetitive transcranial magnetic stimulation (TMS) opens new therapeutic options in neuropsychiatric disorders. The use of rTMS in depressive disorders has been most preferably investigated in clinical trials. In Germany, the application of rTMS outside of clinical trials is already increasingly common, not only for depression. Our nationwide survey in psychiatric hospitals was used to detect the current state of the application of rTMS in clinical practice, and should serve as a basis for the development of quality standards.

Attachment style and oxytocin receptor gene variation interact in influencing social anxiety

OBJECTIVES

Social anxiety has been suggested to be promoted by an insecure attachment style. Oxytocin is discussed as a mediator of trust and social bonding as well as a modulator of social anxiety. Applying a gene-environment (G × E) interaction approach, in the present pilot study the main and interactive effects of attachment styles and oxytocin receptor (OXTR) gene variation were probed in a combined risk factor model of social anxiety in healthy probands.

METHODS

Participants (N = 388; 219 females, 169 males; age 24.7 ± 4.7 years) were assessed for anxiety in social situations (Social Phobia and Anxiety Inventory) depending on attachment style (Adult Attachment Scale, AAS) and OXTR rs53576 A/G genotype.

RESULTS

A less secure attachment style was significantly associated with higher social anxiety. This association was partly modulated by OXTR genotype, with a stronger negative influence of a less secure attachment style on social anxiety in A allele carriers as compared to GG homozygotes.

CONCLUSIONS

The present pilot data point to a strong association of less secure attachment and social anxiety as well as to a gene-environment interaction effect of OXTR rs53576 genotype and attachment style on social anxiety possibly constituting a targetable combined risk marker of social anxiety disorder.

[Pharmacotherapy of Anxiety Disorders]

Anxiety disorders belong to the most frequent psychiatric disorders according to epidemiological studies and are associated with a high economic burden. Panic disorder, generalized anxiety disorder, social anxiety disorder, and specific phobia belong to the most important clinical disorders. The etiology is complex, including genetic, neurobiological as well as psychosocial factors. With regard to treatment, both psychotherapy and medication can be employed according to current treatment guidelines. With regard to psychotherapy, cognitive behavioral therapy (CBT) represents the treatment of choice. As for pharmacological treatment, in particular modern antidepressants and pregabalin are recommended. However, several recommendations have to be considered in daily clinical practice.

Differing brain structural correlates of familial and environmental risk for major depressive disorder revealed by a combined VBM/pattern recognition approach

BACKGROUND

Neuroimaging traits of either familial or environmental risk for major depressive disorder (MDD) have been interpreted as possibly useful vulnerability markers. However, the simultaneous occurrence of familial and environmental risk might prove to be a major obstacle in the attempt of recent studies to confine the precise impact of each of these conditions on brain structure. Moreover, the exclusive use of group-level analyses does not permit prediction of individual illness risk which would be the basic requirement for the clinical application of imaging vulnerability markers. Hence, we aimed to distinguish between brain structural characteristics of familial predisposition and environmental stress by using both group- and individual-level analyses.

METHOD

We investigated grey matter alterations between 20 healthy control subjects (HC) and 20 MDD patients; 16 healthy first-degree relatives of MDD patients (FH+) and 20 healthy subjects exposed to former childhood maltreatment (CM+) by using a combined VBM/pattern recognition approach.

RESULTS

We found similar grey matter reductions in the insula and the orbitofrontal cortex in patients and FH+ subjects and in the hippocampus in patients and CM+ subjects. No direct overlap in grey matter alterations was found between FH+ and CM+ subjects. Pattern classification successfully detected subjects at risk for the disease even by strictly focusing on morphological traits of MDD.

CONCLUSIONS

Familial and environmental risk factors for MDD are associated with differing morphometric anomalies. Pattern recognition might be a promising instrument in the search for and future application of vulnerability markers for MDD.

[Neuropsychological treatment of cognitive deficits in substance abuse disorders, affective disorders, anxiety disorders and obsessive-compulsive disorders - current status and perspectives]

Neuropsychological treatment represents a promising therapeutic approach in the amelioration of cognitive deficits in many neuropsychiatric disorders. Cognitive impairment constitutes a core feature that often persists beyond psychopathological symptoms having a significant impact on psychosocial functioning. However, research interest and evidence of efficacy vary considerably between disease groups. Although neuropsychological treatment is frequently used in clinical practice, there are, with the exception of schizophrenia, relatively few studies on its effectiveness.

Multimodal imaging of a tescalcin (TESC)-regulating polymorphism (rs7294919)-specific effects on hippocampal gray matter structure

In two large genome-wide association studies, an intergenic single-nucleotide polymorphism (SNP; rs7294919) involved in TESC gene regulation has been associated with hippocampus volume. Further characterization of neurobiological effects of the TESC gene is warranted using multimodal brain-wide structural and functional imaging. Voxel-based morphometry (VBM8) was used in two large, well-characterized samples of healthy individuals of West-European ancestry (Münster sample, N=503; SHIP-TREND, N=721) to analyze associations between rs7294919 and local gray matter volume. In subsamples, white matter fiber structure was investigated using diffusion tensor imaging (DTI) and limbic responsiveness was measured by means of functional magnetic resonance imaging (fMRI) during facial emotion processing (N=220 and N=264, respectively). Furthermore, gene x environment (G × E) interaction and gene x gene interaction with SNPs from genes previously found to be associated with hippocampal size (FKBP5, Reelin, IL-6, TNF-α, BDNF and 5-HTTLPR/rs25531) were explored. We demonstrated highly significant effects of rs7294919 on hippocampal gray matter volumes in both samples. In whole-brain analyses, no other brain areas except the hippocampal formation and adjacent temporal structures were associated with rs7294919. There were no genotype effects on DTI and fMRI results, including functional connectivity measures. No G × E interaction with childhood maltreatment was found in both samples. However, an interaction between rs7294919 and rs2299403 in the Reelin gene was found that withstood correction for multiple comparisons. We conclude that rs7294919 exerts highly robust and regionally specific effects on hippocampal gray matter structures, but not on other neuropsychiatrically relevant imaging markers. The biological interaction between TESC and RELN pointing to a neurodevelopmental origin of the observed findings warrants further mechanistic investigations.

The functional -1019C/G HTR1A polymorphism and mechanisms of fear

Serotonin receptor 1A gene (HTR1A) knockout mice show pronounced defensive behaviour and increased fear conditioning to ambiguous conditioned stimuli. Such behaviour is a hallmark of pathological human anxiety, as observed in panic disorder with agoraphobia (PD/AG). Thus, variations in HTR1A might contribute to neurophysiological differences within subgroups of PD/AG patients. Here, we tested this hypothesis by combining genetic with behavioural techniques and neuroimaging. In a clinical multicentre trial, patients with PD/AG received 12 sessions of manualized cognitive-behavioural therapy (CBT) and were genotyped for HTR1A rs6295. In four subsamples of this multicentre trial, exposure behaviour (n=185), defensive reactivity measured using a behavioural avoidance test (BAT; before CBT: n=245; after CBT: n=171) and functional magnetic resonance imaging (fMRI) data during fear conditioning were acquired before and after CBT (n=39). HTR1A risk genotype (GG) carriers more often escaped during the BAT before treatment. Exploratory fMRI results suggest increased activation of the amygdala in response to threat as well as safety cues before and after treatment in GG carriers. Furthermore, GG carriers demonstrated reduced effects of CBT on differential conditioning in regions including the bilateral insulae and the anterior cingulate cortex. Finally, risk genotype carriers demonstrated reduced self-initiated exposure behaviour to aversive situations. This study demonstrates the effect of HTR1A variation on defensive behaviour, amygdala activity, CBT-induced neural plasticity and normalization of defence behaviour in PD/AG. Our results, therefore, translate evidence from animal studies to humans and suggest a central role for HTR1A in differentiating subgroups of patients with anxiety disorders.

The interaction of early life experiences with COMT val158met affects anxiety sensitivity

The pathogenesis of anxiety disorders is considered to be multifactorial with a complex interaction of genetic factors and individual environmental factors. Therefore, the aim of this study was to examine gene-by-environment interactions of the genes coding for catechol-O-methyltransferase (COMT) and monoamine oxidase A (MAOA) with life events on measures related to anxiety. A sample of healthy subjects (N = 782; thereof 531 women; mean age M = 24.79, SD = 6.02) was genotyped for COMT rs4680 and MAOA-uVNTR (upstream variable number of tandem repeats), and was assessed for childhood adversities [Childhood Trauma Questionnaire (CTQ)], anxiety sensitivity [Anxiety Sensitivity Index (ASI)] and anxious apprehension [Penn State Worry Questionnaire (PSWQ)]. Main and interaction effects of genotype, environment and gender on measures related to anxiety were assessed by means of regression analyses. Association analysis showed no main gene effect on either questionnaire score. A significant interactive effect of childhood adversities and COMT genotype was observed: Homozygosity for the low-active met allele and high CTQ scores was associated with a significant increment of explained ASI variance [R(2) = 0.040, false discovery rate (FDR) corrected P = 0.04]. A borderline interactive effect with respect to MAOA-uVNTR was restricted to the male subgroup. Carriers of the low-active MAOA allele who reported more aversive experiences in childhood exhibited a trend for enhanced anxious apprehension (R(2) = 0.077, FDR corrected P = 0.10). Early aversive life experiences therefore might increase the vulnerability to anxiety disorders in the presence of homozygosity for the COMT 158met allele or low-active MAOA-uVNTR alleles.

Neuronal network of panic disorder: the role of the neuropeptide cholecystokinin

Panic disorder (PD) is characterized by panic attacks, anticipatory anxiety and avoidance behavior. Its pathogenesis is complex and includes both neurobiological and psychological factors. With regard to neurobiological underpinnings, anxiety in humans seems to be mediated through a neuronal network, which involves several distinct brain regions, neuronal circuits and projections as well as neurotransmitters. A large body of evidence suggests that the neuropeptide cholecystokinin (CCK) might be an important modulator of this neuronal network. Key regions of the fear network, such as amygdala, hypothalamus, peraqueductal grey, or cortical regions seem to be connected by CCKergic pathways. CCK interacts with several anxiety-relevant neurotransmitters such as the serotonergic, GABA-ergic and noradrenergic system as well as with endocannabinoids, NPY and NPS. In humans, administration of CCK-4 reliably provokes panic attacks, which can be blocked by antipanic medication. Also, there is some support for a role of the CCK system in the genetic pathomechanism of PD with particularly strong evidence for the CCK gene itself and the CCK-2R (CCKBR) gene. Thus, it is hypothesized that genetic variants in the CCK system might contribute to the biological basis for the postulated CCK dysfunction in the fear network underlying PD. Taken together, a large body of evidence suggests a possible role for the neuropeptide CCK in PD with regard to neuroanatomical circuits, neurotransmitters and genetic factors. This review article proposes an extended hypothetical model for human PD, which integrates preclinical and clinical findings on CCK in addition to existing theories of the pathogenesis of PD.

Mechanism of action in CBT (MAC): methods of a multi-center randomized controlled trial in 369 patients with panic disorder and agoraphobia

Cognitive behavioral therapy (CBT) is efficacious for panic disorder with agoraphobia (PD/A). Nevertheless, the active ingredients of treatment and the mechanisms through which CBT achieves its effects remain largely unknown. The mechanisms of action in CBT (MAC) study was established to investigate these questions in 369 patients diagnosed with PD/A. The MAC study utilized a multi-center, randomized controlled design, with two active treatment conditions in which the administration of exposure was varied, and a wait-list control group. The special feature of MAC is the way in which imbedded experimental, psychophysiological, and neurobiological paradigms were included to elucidate therapeutic and psychopathological processes. This paper describes the aims and goals of the MAC study and the methods utilized to achieve them. All aspects of the research design (e.g., assessments, treatment, experimental procedures) were implemented so as to facilitate the detection of active therapeutic components, and the mediators and moderators of therapeutic change. To this end, clinical, behavioral, physiological, experimental, and genetic data were collected and will be integrated.

Effects of experimentally induced panic attacks on neuroimmunological markers

Since little is known concerning regulation of immunological parameters in rapid changing psychiatric states like panic attacks, we measured cytokines at different time points in healthy subjects, which underwent experimental panic induction using the CCK-4 paradigm. Apart from a challenge related IL-6 increase, we could not observe any changes of neuroimmunological markers in relation to acute anxiety with regard to time and group. Herein we conducted for the first time a new approach to immunological research in panic disorder, suggesting immune changes are more related to long term disease stress.

Comparison of combined psycho- and pharmacotherapy with monotherapy in anxiety disorders: controversial viewpoints and clinical perspectives

Anxiety disorders are among the most frequent psychiatric disorders. Experimental evidence supports both psychotherapy as well as pharmacotherapy as effective treatments. There is, however, a controversy concerning the efficacy of a combination of both approaches. While some studies suggest that combined treatment enhances efficacy, others report conflicting results. This article traces the positions in this debate. We present the results from two recent meta-analyses and discuss implications for clinical practice and further research. We suggest that a research strategy that strives to establish differential indications based on patient characteristics should be preferred over attempts to reach a global judgement of the question, which appears too simplistic given the complexity of the issue.

GABAergic and endocannabinoid dysfunction in anxiety - future therapeutic targets?

With a lifetime prevalence of up to 25% anxiety disorders are among the most frequently occurring psychiatric disorders. The etiology of anxiety is considered to be multifactorial with an interaction of neurobiological, psychological and environmental factors. With regard to neurobiological factors, several neurochemical systems and neuroanatomical circuits have been discussed to be involved. In particular, anxiety might be a result of insufficient inhibitory control, pointing towards a major role of the gamma-amino-butyric acid (GABA) system in these disorders. Preclinical and clinical studies discuss a decreased GABAergic inhibition in anxiety and patients with anxiety disorders. In view of these findings it is intriguing that benzodiazepines, which currently represent the most potent and powerful anxiolytic agents, act through an enhancement of GABAergic inhibition targeting the GABAA receptor. Thus, it has been suggested that the GABAergic system might represent a promising future target for new pharmacologic strategies for the treatment of anxiety. Closely linked to the GABAergic system is the endocannabinoid system, which might also play an important role in this group of disorders. The endocannabinoid system has particularly been involved in extinction learning, suggesting a key role of this system in the process of fear extinction. In this paper, both the GABAergic and the endocannabinoid system will be reviewed with regard to their role in anxiety and anxiety disorders in humans with particular attention to findings from genetic and neuroimaging studies. Moreover, both systems will be discussed as potential therapeutic targets.

[Anxiety disorders. Causes, clinical picture and treatment]

Anxiety disorders are among the most frequent mental disorders together with affective disorders with a lifetime prevalence of 18%. The pathogenesis of these disorders is complex and includes biological and psychosocial factors. Modern diagnostic classification systems (ICD-10, DSM-IV) differentiate between panic disorder with or without agoraphobia, generalized anxiety disorder, social phobia and specific phobia. Recommended treatment approaches include psychotherapy as well as pharmacotherapy, which have to be preceded by an empathic psychoeducation. Today, cognitive behavioural psychotherapy and modern antidepressants such as selective serotonin reuptake inhibitors represent the first-line therapy of most anxiety disorders. This review gives an overview of pathogenesis, clinical presentation and current treatment standards.

Polymorphisms in the angiotensin-converting enzyme gene are associated with unipolar depression, ACE activity and hypercortisolism

Angiotensin-converting enzyme (ACE) is assumed to influence the activity of the hypothalamic-pituitary-adrenocortical (HPA) system, which shows hyperactivity in the majority of patients with major depression. The ACE gene, known to be associated with cardiovascular disorders, which in turn are accompanied with an increased susceptibility for depression, is therefore a promising candidate gene for affective disorders. We investigated the genetic association between 35 single-nucleotide polymorphisms (SNPs) and an insertion/deletion (I/D)-polymorphism in the ACE gene and the susceptibility for unipolar major depression together with the genetic association with ACE serum activity and functional parameters of the HPA system. Two independent case/control samples with a total of 843 unrelated unipolar depressed patients and 1479 healthy controls were investigated. A case/control sample was screened to detect genetic associations with unipolar major depression. In addition, a replication sample was used to confirm the detected associations and to further investigate functional consequences of the genetic variants associated with depression. In the screening sample, two SNPs within the ACE gene were significantly associated with unipolar major depression. The association with unipolar major depression of one SNP (rs4291) located in the promoter region of the ACE gene was confirmed in our replication sample. The T-allele of this SNP was associated with depression and depressed T-allele carriers showed higher ACE serum activity and HPA-axis hyperactivity. Variants of the ACE gene such as SNP rs4291 are suggested susceptibility factors for unipolar major depression. We could show that SNP rs4291 influences ACE activity and HPA-axis hyperactivity and might therefore represent a common pathophysiologic link for unipolar depression and cardiovascular disease.

Neuroactive steroids as modulators of depression and anxiety

Certain neuroactive steroids modulate ligand-gated ion channels via non-genomic mechanisms. Especially 3alpha-reduced pregnane steroids are potent positive allosteric modulators of the GABA type A-receptor. During major depression there is a dysequilibrium of 3alpha-reduced neuroactive steroids, which is corrected by clinically effective pharmacological treatment. To investigate whether these alterations are a general principle of successful antidepressant treatment we studied the impact of non-pharmacological treatment options on neuroactive steroid concentrations during major depression. Neither partial sleep deprivation, transcranial magnetic stimulation nor electroconvulsive therapy affected neuroactive steroid levels irrespectively of the response to these treatments. These studies suggest that the changes in neuroactive steroids observed after antidepressant pharmacotherapy more likely reflect distinct pharmacological properties of antidepressants rather than the clinical response. In patients with panic disorder changes in neuroactive steroid composition have been observed opposite of those seen in depression. These changes may represent counterregulatory mechanisms against the occurrence of spontaneous panic attacks. However, during experimental panic induction with either cholecystokinin-tetrapeptide or sodium lactate there was a pronounced decline in the concentrations of 3alpha-reduced neuroactive steroids in patients with panic disorder, which might result in a decreased GABAergic tone. In contrast, no changes in neuroactive steroid concentrations could be observed in healthy controls with the exception of 3alpha, 5alpha-tetrahydrodeoxycorticosterone, allotetrahydrodeoxycorticosterone. The modulation of GABA type A-receptors by neuroactive steroids might contribute to the pathophysiology of depression and anxiety disorders and might offer new targets for the development of novel anxiolytic compounds.

SNP and haplotype analysis of a novel tryptophan hydroxylase isoform (TPH2) gene provide evidence for association with major depression

Tryptophan hydroxylase (TPH), being the rate-limiting enzyme in the biosynthesis of serotonin plays a major role as candidate gene in several psychiatric disorders. Recently, a second TPH isoform (TPH2) was identified in mice, which was exclusively present in the brain. In a previous post-mortem study of our own group, we could demonstrate that TPH2 is also expressed in the human brain, but not in peripheral tissues. This is the first report of an association study between polymorphisms in the TPH2 gene and major depression (MD). We performed single-nucleotide polymorphism (SNP), haplotype and linkage disequlibrium studies on 300 depressed patients and 265 healthy controls with 10 SNPs in the TPH2 gene. Significant association was detected between one SNP (P=0.0012, global P=0.0051) and MD. Haplotype analysis produced additional support for association (P<0.0001, global P=0.0001). Our findings provide evidence for an involvement of genetic variants of the TPH2 gene in the pathogenesis of MD and might be a hint on the repeatedly discussed duality of the serotonergic system. These results may open up new research strategies for the analysis of the observed disturbances in the serotonergic system in patients suffering from several other psychiatric disorders.