Predictors of the placebo response in a nutraceutical randomized controlled trial for depression

OBJECTIVE

The placebo response in depression studies is the change in symptoms amongst those who receive an inactive treatment. Many well-designed randomized controlled trials (RCTs) of depression have a high proportion of placebo responders, with little understanding as to why. The present study assesses characteristics associated with the placebo response in a nutraceutical trial with a large proportion of placebo responders.

METHODS

This is a secondary analysis of a nutraceutical depression RCT which identified no overall treatment benefit relative to placebo (n = 69 in placebo group). We investigated participant characteristics such as socio-demographics, clinical features, and recruitment methods, and their association with the placebo response. Monoaminergic genetic polymorphisms were also assessed. Placebo response was measured based on change in Montgomery-Asberg Depression Rating Scale score. The association of these hypothesis-driven variables of interest and the placebo response was examined using linear mixed effects models.

RESULTS

Greater levels of education, particularly pursuing post-high school education, better self-reported general health, marriage/de facto, greater improvement in the first trial week, and more failed antidepressant therapies in the current depressive episode were associated with greater placebo response. An increased placebo response was not found in those recruited via social media nor in those with concomitant antidepressant therapy. Single nucleotide polymorphisms from the tryptophan hydroxylase 1 (TPH1) gene (A779C and A218C) were weakly associated with greater placebo response, although the evidence was attenuated after accounting for multiple comparisons.

CONCLUSION

This is, to our knowledge, the first study within nutraceutical research for depression to assess the association between participant characteristics and variation in the placebo response. Several variables appeared to predict the placebo response. Such findings may encourage future trial designs which could dampen placebo response, improve assay sensitivity, and allow for treatment effects to be potentially more detectable. Please cite this article as: Arnold R, Murphy-Smith J, Ng CH, Mischoulon D, Byrne GJ, Bousman CA, Stough C, Berk M, Sarris J. Predictors of the placebo response in a nutraceutical randomized controlled trial for depression. J Integr Med. 2024; 22(1): 46-53.

Pharmacotherapy for Depression and Anxiety in the Primary Care Setting

The prevalence of mental health disorders is rising with the coronavirus of 2019 pandemic, and millions of Americans reside in areas with mental health professional shortages. Primary care providers have an opportunity to provide care for commonly occurring mental health disorders. Using a holistic conceptualization of recovery in mental illness, this report provides evidence-based guidance for initiation, titration, and discontinuation of pharmacotherapy for mild to moderate depression and anxiety in the primary care setting. The use of measurement-based care, selection of appropriate class and agent for individual candidates, and patient education are addressed. Best practices for troubleshooting, titration, and referral are discussed.

Differential effects of psychoactive substances on human wildtype and polymorphic T356M dopamine transporters (DAT)

Many psychoactive substances affect the human dopamine (DA) reuptake transporter (hDAT). Polymorphisms in the encoding gene could affect the functionality of the transporter and consequently alter effects of psychotropic and recreational drugs. Recently, a T356 M single nucleotide polymorphism in the human SLC6A3 gene was described, which resulted in functional impairments of DA uptake. Therefore, we investigated the effects of 10 psychoactive substances (0.01-1000 μM)) on DA uptake in human embryonic kidney (HEK) 293 cells transiently overexpressing wildtype (WT) or T356 M hDAT. Our data shows that T356 M hDAT has a 3 times lower V_max and a 3 times higher K_m compared to WT hDAT. Additionally, all psychoactive substances inhibited DA uptake by T356 M and WT hDAT. The DA reuptake inhibitors (methylphenidate, cocaine, and bupropion) inhibited DA uptake by WT hDAT most potently, followed by amphetamine-type stimulants [4-fluoroamphetamine (4-FA), amphetamine and MDMA], selective serotonin reuptake inhibitors (SSRI; fluoxetine and citalopram) and arylcyclohexylamines [methoxetamine (MXE) and ketamine]. Compared to DA uptake by WT hDAT, bupropion, methylphenidate, cocaine, and MXE less potently inhibited DA uptake by T356 M hDAT, while citalopram more potently inhibited uptake. The differences in IC₅₀ values between T356 M and WT hDAT were considerable (3-45 fold). As such, the presence of this polymorphism could affect treatment efficiency with these substances as well as susceptibly for toxicity and addiction for individuals carrying this polymorphism.

Gene × Environment Interaction in Developmental Disorders: Where Do We Stand and What's Next?

Although the field of psychiatry has witnessed the proliferation of studies on Gene × Environment (G×E) interactions, still limited is the knowledge we possess of G×E interactions regarding developmental disorders. In this perspective paper, we discuss why G×E interaction studies are needed to broaden our knowledge of developmental disorders. We also discuss the different roles of hazardous versus self-generated environmental factors and how these types of factors may differentially engage with an individual's genetic background in predicting a resulting phenotype. Then, we present examplar studies that highlight the role of G×E in predicting atypical developmental trajectories as well as provide insight regarding treatment outcomes. Supported by these examples, we explore the need to move beyond merely examining statistical interactions between genes and the environment, and the motivation to investigate specific genetic susceptibility and environmental contexts that drive developmental disorders. We propose that further parsing of genetic and environmental components is required to fully understand the unique contribution of each factor to the etiology of developmental disorders. Finally, with a greater appreciation of the complexities of G×E interaction, this discussion will converge upon the potential implications for clinical and translational research.

Association of DNA methylation in BDNF with escitalopram treatment response in depressed Chinese Han patients

PURPOSE

The neurotrophin brain-derived neurotrophic factor (BDNF) has been found to be associated with both the pathophysiology of depression and antidepressants response. Gene expression differences were partly mediated by SNP, which might be identified as a predictor of antidepressant response. In the present study, we attempt to identify whether DNA methylation, another factor known to affect gene transcription, might also predict antidepressant response.

METHODS

A total of 85 depressed Chinese Han patients were followed-up 8 weeks after initiating escitalopram treatment. Treatment response was assessed by changes in the Hamilton Depression Rating Scale-17 (HAMD-17) score. The Life Events Scale (LES) and the Childhood Trauma Questionnaire (CTQ) were utilized as the assessment of previous life stress. The bisulfate sequencing was used to assess DNA methylation. Four single nucleotide polymorphisms (SNPs) in the BDNF gene were genotyped using PCR-RFLP or PCR sequencing.

RESULTS

We identified a DNA methylation predictor (P = 0.006-0.036) and a DNA methylation by LES interaction predictor (OR = 1.442 [1.057-1.968], P = 0.021) of general antidepressant treatment response. Lower mean BDNF DNA methylation was associated with impaired antidepressant response. Furthermore, the present data indicated that age, life stress, and SNPs genotype might be likely related to DNA methylation status. Average DNA methylation of BDNF at baseline was significantly lower than that at endpoint after 8 weeks of escitalopram treatment, which was based only on a subset of cases (n = 44).

CONCLUSIONS

Our results suggest that BDNF DNA hypomethylation and its interaction with lower LES score might result in impaired antidepressant treatment response. The pharmacoepigenetic study could eventually help in finding epigenetic biomarkers of antidepressant response.

The stability and change of etiological influences on depression, anxiety symptoms and their co-occurrence across adolescence and young adulthood

BACKGROUND

Depression and anxiety persist within and across diagnostic boundaries. The manner in which common v. disorder-specific genetic and environmental influences operate across development to maintain internalizing disorders and their co-morbidity is unclear. This paper investigates the stability and change of etiological influences on depression, panic, generalized, separation and social anxiety symptoms, and their co-occurrence, across adolescence and young adulthood.

METHOD

A total of 2619 twins/siblings prospectively reported symptoms of depression and anxiety at mean ages 15, 17 and 20 years.

RESULTS

Each symptom scale showed a similar pattern of moderate continuity across development, largely underpinned by genetic stability. New genetic influences contributing to change in the developmental course of the symptoms emerged at each time point. All symptom scales correlated moderately with one another over time. Genetic influences, both stable and time-specific, overlapped considerably between the scales. Non-shared environmental influences were largely time- and symptom-specific, but some contributed moderately to the stability of depression and anxiety symptom scales. These stable, longitudinal environmental influences were highly correlated between the symptoms.

CONCLUSIONS

The results highlight both stable and dynamic etiology of depression and anxiety symptom scales. They provide preliminary evidence that stable as well as newly emerging genes contribute to the co-morbidity between depression and anxiety across adolescence and young adulthood. Conversely, environmental influences are largely time-specific and contribute to change in symptoms over time. The results inform molecular genetics research and transdiagnostic treatment and prevention approaches.

Behavioral and molecular responses to electroconvulsive shock differ between genetic and environmental rat models of depression

Depression׳s causes play a role in individuals׳ different responses to antidepressant treatments, which require advancements. We investigated the mechanisms behind and responses to a highly effective antidepressant treatment, electroconvulsive therapy (ECT), in rat models with different (genetic or environmental) depression causes. Wistar Kyoto (WKY) rats and Wistar rats treated with chronic unpredictable mild stresses (CUMS) were used as genetic and environmental rat models of depression, respectively. The rats underwent electroconvulsive shock (ECS, the animal analog of ECT) or sham ECS. We performed a sucrose preference test, open field test, and Morris water maze to assess behavior. Hippocampal neuron numbers were measured with Nissl stain. Hippocampal BDNF, CREB, and p-CREB proteins were assayed with ELISA or western blotting. The main results showed that ECS impaired WKY rats׳ memories but improved CUMS rats׳ memories. It elevated hippocampal BDNF and CREB proteins only in CUMS rats, while it improved depressive behavior and hippocampal p-CREB protein levels in both rats, with more effective regulations in the CUMS rats. ECS did not change the hippocampal neuron number in both rats. These findings suggest that ECS exerted up-regulating effects on hippocampal BDNF and CREB (and its phosphorylation) in depressed rats, and the environmental model responded better.

The usefulness of genotyping cytochrome P450 enzymes in the treatment of depression

INTRODUCTION

Pharmacogenomics, which is derived from genome-wide association studies (GWAS), and pharmacogenetics, which involves candidate gene association studies (CGASs), are proving increasingly useful in personalized cancer care. Research in psychiatric applications has primarily involved genetic polymorphisms of P450 CYP enzymes, which mediate oxidative metabolism, particularly CYP2D6, which is involved in the metabolism of at least 30 psychotropic medications. This work has been supplemented by genotyping of proteins for the drug efflux pump P-glycoprotein (P-gp), serotonin receptors, and the serotonin reuptake pump.

AREAS COVERED

This review covers principles of pharmacogenetics and pharmacogenomics, previous analyses of pharmacokinetic and pharmacodynamics studies, newer studies of the predictive value of genetic testing in the treatment of depression, obstacles to implementation of genetic testing in predicting treatment response and side effects, and suggestions for future research.

EXPERT OPINION

Studies of multiple genes have produced some positive results in groups of patients, but genetic testing does not yet seem to be applicable to choosing medications for a specific patient.

Searching the cytochrome p450 enzymes for the metabolism of meranzin hydrate: a prospective antidepressant originating from Chaihu-Shugan-San

Meranzin hydrate (MH), an absorbed bioactive compound from the Traditional Chinese Medicine (TCM) Chaihu-Shugan-San (CSS), was first isolated in our laboratory and was found to possess anti-depression activity. However, the role of cytochrome P450s (CYPs) in the metabolism of MH was unclear. In this study, we screened the CYPs for the metabolism of MH in vitro by human liver microsomes (HLMs) or human recombinant CYPs. MH inhibited the enzyme activities of CYP1A2 and CYP2C19 in a concentration-dependent manner in the HLMs. The Km and Vmax values of MH were 10.3±1.3 µM and 99.1±3.3 nmol/mg protein/min, respectively, for the HLMs; 8.0±1.6 µM and 112.4±5.7 nmol/nmol P450/min, respectively, for CYP1A2; and 25.9±6.6 µM and 134.3±12.4 nmol/nmol P450/min, respectively, for CYP2C19. Other human CYP isoforms including CYP2A6, CYP2C9, CYP2D6, CYP2E1 and CYP3A4 showed minimal or no effect on MH metabolism. The results suggested that MH was simultaneously a substrate and an inhibitor of CYP1A2 and CYP2C9, and MH had the potential to perpetrate drug-drug interactions with other CYP1A2 and CYP2C19 substrates.

Behavior genetics: past, present, future

The disciplines of developmental psychopathology and behavior genetics are concerned with many of the same questions about the etiology and course of normal and abnormal behavior and about the factors that promote typical development despite the presence of risk. The goal of this paper is to summarize how research in behavior genetics has shed light on questions that are central to developmental psychopathology. We briefly review the origins of behavior genetics, summarize the findings that have been gleaned from several decades of quantitative and molecular genetics research, and describe future directions for research that will delineate gene function as well as pathways from genes to brain to behavior. The importance of environmental contributions, at both genetic and epigenetic levels, will be discussed. We conclude that behavior genetics has made significant contributions to developmental psychopathology by documenting the interplay among risk and protective factors at multiple levels of the organism, by clarifying the causal status of risk exposures, and by identifying factors that account for change and stability in psychopathology. As the tools to identify gene function become increasingly sophisticated, and as behavioral geneticists become increasingly interdisciplinary in their scope, the field is poised to make ever greater contributions to our understanding of typical and atypical development.

Therapygenetics: 5-HTTLPR genotype predicts the response to exposure therapy for agoraphobia

This study was intended to assess the extent to which the low-expression allele of the serotonin transporter gene promoter predicts better response to exposure-based behavior therapy in patients with panic disorder with agoraphobia (PDA). Ninety-nine patients with PDA underwent a 1-week in vivo exposure-based behavior therapy program and provided saliva samples to extract genomic DNA and classify individuals according to four allelic forms (SA, SG, LA, LG) of the 5-HTT-linked polymorphic region (5-HTTLPR). We determined whether the 5-HTTLPR genotype predicted change in avoidance behavior in PDA following treatment. After controlling for pre-treatment avoidance behavior, the 5-HTTLPR low-expression genotypes showed a more favorable response to exposure therapy two weeks following treatment, compared to the other patients. This study suggests a genetic contribution to treatment outcome following behavior therapy and implicates the serotonergic system in response to exposure-based treatments in PDA.

Race, genetic ancestry and response to antidepressant treatment for major depression

The Sequenced Treatment Alternatives to Relieve Depression (STAR*D) Study revealed poorer antidepressant treatment response among black compared with white participants. This racial disparity persisted even after socioeconomic and baseline clinical factors were taken into account. Some studies have suggested genetic contributions to this disparity, but none have attempted to disentangle race and genetic ancestry. Here we used genome-wide single-nucleotide polymorphism (SNP) data to examine independent contributions of race and genetic ancestry to citalopram response. Secondary data analyses included 1877 STAR*D participants who completed an average of 10 weeks of citalopram treatment and provided DNA samples. Participants reported their race as White (n=1464), black (n=299) or other/mixed (n=114). Genetic ancestry was estimated by multidimensional scaling (MDS) analyses of about 500 000 SNPs. Ancestry proportions were estimated by STRUCTURE. Structural equation modeling was used to examine the direct and indirect effects of observed and latent predictors of response, defined as change in the Quick Inventory of Depressive Symptomatology (QIDS) score from baseline to exit. Socioeconomic and baseline clinical factors, race, and anxiety significantly predicted response, as previously reported. However, direct effects of race disappeared in all models that included genetic ancestry. Genetic African ancestry predicted lower treatment response in all models. Although socioeconomic and baseline clinical factors drive racial differences in antidepressant response, genetic ancestry, rather than self-reported race, explains a significant fraction of the residual differences. Larger samples would be needed to identify the specific genetic mechanisms that may be involved, but these findings underscore the importance of including more African-American patients in drug trials.

Treatment response for acute depression is not associated with number of previous episodes: lack of evidence for a clinical staging model for major depressive disorder

Mental illness has been observed to follow a neuroprogressive course, commencing with prodrome, then onset, recurrence and finally chronic illness. In bipolar disorder and schizophrenia responsiveness to treatment mirrors these stages of illness progression, with greater response to treatment in the earlier stages of illness and greater treatment resistance in chronic late stage illness. Using data from 5627 participants in 15 controlled trials of duloxetine, comparator arm (paroxetine, venlafaxine, escitalopram) or placebo for the treatment of an acute depressive episode, the relationship between treatment response and number of previous depressive episodes was determined. Data was dichotomised for comparisons between participants who had >3 previous episodes (n=1697) or ≤3 previous episodes (n=3930), and additionally for no previous episodes (n=1381) or at least one previous episode (n=4246). Analyses were conducted by study arm for each clinical trial, and results were then pooled. There was no significant difference between treatment response and number of previous depressive episodes. This unexpected finding suggests that treatments to reduce symptoms of depression during acute illness do not lose efficacy for patients with a longer history of illness.

A genome-wide association study of a sustained pattern of antidepressant response

Genome-wide association studies (GWAS) have failed to replicate common genetic variants associated with antidepressant response, as defined using a single endpoint. Genetic influences may be discernible by examining individual variation between sustained versus unsustained patterns of response, which may distinguish medication effects from non-specific, or placebo responses to active medication. We conducted a GWAS among 1116 subjects with Major Depressive Disorder from the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) trial who were characterized using Growth Mixture Modeling as showing a sustained versus unsustained pattern of clinical response over 12 weeks of treatment with citalopram. Replication analyses examined 585 subjects from the Genome-based Therapeutic Drugs for Depression (GENDEP) trial. The strongest association with sustained as opposed to unsustained response in STAR*D involved a single nucleotide polymorphism (SNP; rs10492002) within the acyl-CoA synthetase short-chain family member 3 gene (ACSS3, p-value=4.5×10(-6), odds ratio=0.61). No SNPs met our threshold for genome-wide significance. SNP data were available in GENDEP for 18 of the top 25 SNPs in STAR*D. The most replicable association was with SNP rs7816924 (p=0.008, OR=1.58); no SNP met the replication p-value threshold of 0.003. Joint analysis of these 18 SNPs resulted in the strongest signal coming from rs7816924 (p=2.11×10(-7)), which resides in chondroitin sulfate N-acetylgalactosaminyltransferase 1 gene (CSGALNACT1). An exploratory genetic pathway analysis revealed evidence for an involvement of the KEGG pathway of long-term potentiation (FDR=.02). Results suggest novel genetic associations to sustained response.

Biomarkers predicting antidepressant treatment response: how can we advance the field?

Major depression, affecting an estimated 350 million people worldwide, poses a serious social and economic threat to modern societies. There are currently two major problems calling for innovative research approaches, namely, the absence of biomarkers predicting antidepressant response and the lack of conceptually novel antidepressant compounds. Both, biomarker predicting a priori whether an individual patient will respond to the treatment of choice as well as an early distinction of responders and nonresponders during antidepressant therapy can have a significant impact on improving this situation. Biosignatures predicting antidepressant response a priori or early in treatment would enable an evidence-based decision making on available treatment options. However, research to date does not identify any biologic or genetic predictors of sufficient clinical utility to inform the selection of specific antidepressant compound for an individual patient. In this review, we propose an optimized translational research strategy to overcome some of the major limitations in biomarker discovery. We are confident that early transfer and integration of data between both species, ideally leading to mutual supportive evidence from both preclinical and clinical studies, are most suitable to address some of the obstacles of current depression research.

Gene × environment interactions in the prediction of response to antidepressant treatment

Major depressive disorder (MDD) is responsible for an increasing individual and global health burden. Extensive research on the genetic disposition to develop MDD and to predict the response to antidepressant treatment has yet failed to identify strong genetic effects. The concept of gene × environment interaction takes into account that environmental factors have been identified as important components in the development of MDD and combines both, genetic predisposition and environmental exposure, to elucidate complex traits such as MDD. Here, we review the current research on gene × environment interactions with regard to the development of MDD as well as response to antidepressant treatment. We hypothesize that gene × environment interactions delineate specific biological subtypes of depression and that individuals with such pathophysiological distinct types of depression will likely respond to different treatments. The elucidation of gene × environment interactions may thus not only help to understand the pathophysiology of MDD but could also provide markers for a personalized antidepressant therapy.

Therapygenetics: Using genetic markers to predict response to psychological treatment for mood and anxiety disorders

Considerable variation is evident in response to psychological therapies for mood and anxiety disorders. Genetic factors alongside environmental variables and gene-environment interactions are implicated in the etiology of these disorders and it is plausible that these same factors may also be important in predicting individual differences in response to psychological treatment. In this article, we review the evidence that genetic variation influences psychological treatment outcomes with a primary focus on mood and anxiety disorders. Unlike most past work, which has considered prediction of response to pharmacotherapy, this article reviews recent work in the field of therapygenetics, namely the role of genes in predicting psychological treatment response. As this is a field in its infancy, methodological recommendations are made and opportunities for future research are identified.

Personalized medicine in major depressive disorder -- opportunities and pitfalls

The sequencing of the human genome in the early days of this millennium was greeted with great fanfare as this accomplishment was expected to revolutionize medicine and result in individualized treatments based on the genetic make-up of the patient. The ultimate promise of personalized medicine would be fulfilled with the identification of disease biomarkers that would be widely available for use in diagnosis and treatment. Progress, however, has been slow in providing disease biomarkers or approved diagnostic tests. This is true for major depressive disorder (MDD), despite its prevalence in the general population and the widespread acceptance of its biological basis. Studies using strategies like genome-wide association and candidate gene analyses have identified a number of possible biomarkers of MDD, including serum levels of neurotrophic factors, inflammatory cytokines and HPA axis hormones, but none have proven sufficiently powerful for clinical use. The lack of biologically based tests available for use in identifying patients with MDD is a significant impediment to personalized and more effective treatment, because it means diagnosis continues to be driven by subjective symptoms. While genetic studies of MDD have not yet led to diagnostic and treatment biomarkers, progress in determining the role of the genome in drug metabolism heralds the first effort in personalized prescribing for the antidepressants. The FDA suggested and approved genotyping tests for common variants of drug metabolism genes, such as the cytochrome p450s. By using these tests a physician can select an appropriate antidepressant for a given patient, as differences in clearance, half-life, and peak blood concentrations are controlled by genetic variability in drug metabolism. Personalization in drug choice can be achieved because these tests: (1) identify responders and non-responders; (2) provide alerts to possible adverse drug events; and (3) help optimize dose. Improved ways of diagnosing and prescribing effective treatments for MDD are needed, as the available methods are inadequate and symptom based. In the foreseeable future, further interrogation of the genome may serve as the basis for development of new personalized medicine strategies for diagnosis and treatment of MDD.

Fluoxetine pharmacogenetics in child and adult populations

Although fluoxetine is useful in the treatment of major depression, 30-40 % of the patients do not respond to therapy. The response seems to be influenced by certain genes which are involved in the drug's pharmacodynamics and pharmacokinetics. The present study reviews the literature on genetic contributions to fluoxetine response in children and adults, and concludes that the different polymorphisms of CYP2D6 and CYP2C9 may influence the blood concentrations of fluoxetine. If the childhood dose is adjusted for weight, differences between children and adults are unlikely. As regards the genes that influence the drug's pharmacodynamics, polymorphisms of SLC6A4, HTR1A and MAO-A seem to be involved in the response to fluoxetine, while the genes COMT, CRHR1, PDEA1, PDEA11 GSK3B and serpin-1 also seem to play a role. Comparison of different studies reveals that the results are not always consistent, probably due to methodological differences. Other factors such as gender or ethnicity may also influence treatment response.

Predictors of remission in depression to individual and combined treatments (PReDICT): study protocol for a randomized controlled trial

BACKGROUND

Limited controlled data exist to guide treatment choices for clinicians caring for patients with major depressive disorder (MDD). Although many putative predictors of treatment response have been reported, most were identified through retrospective analyses of existing datasets and very few have been replicated in a manner that can impact clinical practice. One major confound in previous studies examining predictors of treatment response is the patient's treatment history, which may affect both the predictor of interest and treatment outcomes. Moreover, prior treatment history provides an important source of selection bias, thereby limiting generalizability. Consequently, we initiated a randomized clinical trial designed to identify factors that moderate response to three treatments for MDD among patients never treated previously for the condition.

METHODS/DESIGN

Treatment-naïve adults aged 18 to 65 years with moderate-to-severe, non-psychotic MDD are randomized equally to one of three 12-week treatment arms: (1) cognitive behavior therapy (CBT, 16 sessions); (2) duloxetine (30-60 mg/d); or (3) escitalopram (10-20 mg/d). Prior to randomization, patients undergo multiple assessments, including resting state functional magnetic resonance imaging (fMRI), immune markers, DNA and gene expression products, and dexamethasone-corticotropin-releasing hormone (Dex/CRH) testing. Prior to or shortly after randomization, patients also complete a comprehensive personality assessment. Repeat assessment of the biological measures (fMRI, immune markers, and gene expression products) occurs at an early time-point in treatment, and upon completion of 12-week treatment, when a second Dex/CRH test is also conducted. Patients remitting by the end of this acute treatment phase are then eligible to enter a 21-month follow-up phase, with quarterly visits to monitor for recurrence. Non-remitters are offered augmentation treatment for a second 12-week course of treatment, during which they receive a combination of CBT and antidepressant medication. Predictors of the primary outcome, remission, will be identified for overall and treatment-specific effects, and a statistical model incorporating multiple predictors will be developed to predict outcomes.

DISCUSSION

The PReDICT study's evaluation of biological, psychological, and clinical factors that may differentially impact treatment outcomes represents a sizeable step toward developing personalized treatments for MDD. Identified predictors should help guide the selection of initial treatments, and identify those patients most vulnerable to recurrence, who thus warrant maintenance or combination treatments to achieve and maintain wellness.

Neurotrophic gene polymorphisms and response to psychological therapy

Therapygenetics, the study of genetic determinants of response to psychological therapies, is in its infancy. Here, we investigate whether single-nucleotide polymorphisms in nerve growth factor (NGF) (rs6330) and brain-derived neutrotrophic factor (BDNF) (rs6265) genes predict the response to cognitive behaviour therapy (CBT). Neurotrophic genes represent plausible candidate genes: they are implicated in synaptic plasticity, response to stress, and are widely expressed in brain areas involved in mood and cognition. Allelic variation at both loci has shown associations with anxiety-related phenotypes. A sample of 374 anxiety-disordered children with white European ancestry was recruited from clinics in Reading, UK, and in Sydney, Australia. Participants received manualised CBT treatment and DNA was collected from buccal cells using cheek swabs. Treatment response was assessed at post-treatment and follow-up time points. We report first evidence that children with one or more copies of the T allele of NGF rs6330 were significantly more likely to be free of their primary anxiety diagnosis at follow-up (OR = 0.60 (0.42-0.85), P = 0.005). These effects remained even when other clinically relevant covariates were accounted for (OR = 0.62 (0.41-0.92), P = 0.019). No significant associations were observed between BDNF rs6265 and response to psychological therapy. These findings demonstrate that knowledge of genetic markers has the potential to inform clinical treatment decisions for psychotherapeutic interventions.

Gene-environment interaction in major depression and antidepressant treatment response

Response to antidepressants is interindividually variable. It has been suggested that this variability is a direct consequence of etiological heterogeneity. Therefore, the same genes, environments, and gene-environment interactions implicated in different etiological pathways to depression may also predict response to treatment. This article reviews the evidence relevant to this hypothesis by first outlining the roles of genes, environments, and gene-environment interplay in the etiology of depression, and then considering the same factors in treatment response. Environmental exposures, such as childhood maltreatment, are potent predictors of both depression and treatment response. Although alone genetic factors have failed to consistently predict either phenotype, several polymorphisms have been shown to moderate the effects of environmental adversity on the development of depression and treatment response. These findings suggest that the dissection of etiological pathways to depression may provide the key to understanding and predicting response to antidepressants.

Genomics of Dementia: APOE- and CYP2D6-Related Pharmacogenetics

Dementia is a major problem of health in developed societies. Alzheimer's disease (AD), vascular dementia, and mixed dementia account for over 90% of the most prevalent forms of dementia. Both genetic and environmental factors are determinant for the phenotypic expression of dementia. AD is a complex disorder in which many different gene clusters may be involved. Most genes screened to date belong to different proteomic and metabolomic pathways potentially affecting AD pathogenesis. The ε4 variant of the APOE gene seems to be a major risk factor for both degenerative and vascular dementia. Metabolic factors, cerebrovascular disorders, and epigenetic phenomena also contribute to neurodegeneration. Five categories of genes are mainly involved in pharmacogenomics: genes associated with disease pathogenesis, genes associated with the mechanism of action of a particular drug, genes associated with phase I and phase II metabolic reactions, genes associated with transporters, and pleiotropic genes and/or genes associated with concomitant pathologies. The APOE and CYP2D6 genes have been extensively studied in AD. The therapeutic response to conventional drugs in patients with AD is genotype specific, with CYP2D6-PMs, CYP2D6-UMs, and APOE-4/4 carriers acting as the worst responders. APOE and CYP2D6 may cooperate, as pleiotropic genes, in the metabolism of drugs and hepatic function. The introduction of pharmacogenetic procedures into AD pharmacological treatment may help to optimize therapeutics.

The role of disease characteristics in the ethical debate on personal genome testing

BACKGROUND

Companies are currently marketing personal genome tests directly-to-consumer that provide genetic susceptibility testing for a range of multifactorial diseases simultaneously. As these tests comprise multiple risk analyses for multiple diseases, they may be difficult to evaluate. Insight into morally relevant differences between diseases will assist researchers, healthcare professionals, policy-makers and other stakeholders in the ethical evaluation of personal genome tests.

DISCUSSION

In this paper, we identify and discuss four disease characteristics--severity, actionability, age of onset, and the somatic/psychiatric nature of disease--and show how these lead to specific ethical issues. By way of illustration, we apply this framework to genetic susceptibility testing for three diseases: type 2 diabetes, age-related macular degeneration and clinical depression. For these three diseases, we point out the ethical issues that are relevant to the question whether it is morally justifiable to offer genetic susceptibility testing to adults or to children or minors, and on what conditions.

SUMMARY

We conclude that the ethical evaluation of personal genome tests is challenging, for the ethical issues differ with the diseases tested for. An understanding of the ethical significance of disease characteristics will improve the ethical, legal and societal debate on personal genome testing.

Behavioural genetics of the serotonin transporter

The serotonin transporter is a key regulator of the bioavailability of serotonin and therefore any modulation in the expression or action of the transporter would be expected to have consequences on behaviour. The transporter has therefore become a target for pharmaceutical intervention in behavioural and mood disorders. The search for polymorphic variants in the transporter that would associate with neurological disorders has been extensive but has become focused on two domains which are both termed variable number tandem repeat (VNTR)polymorphisms. Both of these VNTRs are in non-coding DNA and therefore proposed to be mechanistically involved in a disorder through their ability to modulate transcriptional or post-transcriptional regulation of the transporter. The most extensively studied is in the promoter and is a bi-allelic insertion/deletion found in the 50 promoter region of the gene 1.2 kb upstream of the transcriptional start site. This VNTR, termed, 5-HTTLPR was initially identified as two variants containing either, 14 (short/deletion) or 16 (long/insertion) copies of a 22 bp repeat. A second widely studied VNTR found in the non-coding region of the transporter is located within intron 2 and comprises 9, 10 or 12 copies of a16–17 bp repeat termed, STin2.9, STin2.10 and STin2.12, respectively. These VNTR polymorphisms have been associated with a range of behavioural and psychiatric disorders including depression, OCD, anxiety and schizophrenia, however often the lack of reproducibility in different cohorts has led to debate on the actual association of the polymorphisms with this extensive range of neurological conditions. Here we review these two polymorphic VNTRs in depth and relate that to pharmaceutical response, their ability to regulate differential transporter expression, their core involvement in gene-environment interaction and their genetic association with specific disorders.