Polymorphism of the serotonin transporter: implications for the use of selective serotonin reuptake inhibitors

Preliminary Evidence That the Short Allele of 5-HTTLPR Moderates the Association of Psychiatric Symptom Severity on Suicide Attempt: The Example in Obsessive-Compulsive Disorder

BACKGROUND

The severity of symptoms represents an important source of distress in patients with a psychiatric disease. However, the extent to which this endogenous stress factor interacts with genetic vulnerability factors for predicting suicide risks remains unclear.

METHODS

We evaluated whether the severity of symptoms interacts with a genetic vulnerability factor (the serotonin transporter gene-linked promoter region variation) in predicting the frequency of lifetime suicide attempts in patients with a psychiatric disease. Symptom severity and 5-HTTLPR polymorphism were collected from a sample of 95 patients with obsessive-compulsive disorder (OCD). Lifetime suicide attempt was the primary outcome, and antecedent of multiple suicide attempts was the secondary outcome.

RESULTS

The gene-by-symptoms interaction was associated with an excess risk of suicide attempts (OR = 4.39, 95CI[1.44, 13.38], p < 0.009) and of multiple suicide attempts (OR = 4.18, 95CI[1.04, 16.77], p = 0.043). Symptom severity (moderate, severe, or extreme) was associated with an approximately five-fold increase in the odds of a lifetime suicide attempt in patients carrying one or two copies of the short allele of 5-HTTLPR. No such relationship was found for patients carrying the long allele.

CONCLUSION

This study provides preliminary evidence for the gene-by-stress interaction on suicide attempt when stress is operationalized as symptom severity. Progress in suicide research may come from efforts to investigate the gene-by-symptoms interaction hypothesis in a variety of diseases.

Acute trajectories of neural activation predict remission to pharmacotherapy in late-life depression

Pharmacological treatment of major depressive disorder (MDD) typically involves a lengthy trial and error process to identify an effective intervention. This lengthy period prolongs suffering and worsens all-cause mortality, including from suicide, and is typically longer in late-life depression (LLD). Our group has recently demonstrated that during an open-label venlafaxine (serotonin-norepinephrine reuptake inhibitor) trial, significant changes in functional resting state connectivity occurred following a single dose of treatment, which persisted until the end of the trial. In this work, we propose an analysis framework to translate these perturbations in functional networks into predictors of clinical remission. Participants with LLD (N = 49) completed 12-weeks of treatment with venlafaxine and underwent functional magnetic resonance imaging (fMRI) at baseline and a day following a single dose of venlafaxine. Data was collected at rest as well as during an emotion reactivity task and an emotion regulation task. Remission was defined as a Montgomery-Asberg Depression Rating Scale (MADRS) ≤10 for two weeks. We computed eigenvector centrality (whole brain connectivity) and activation during the emotion regulation and emotion reactivity tasks. We employed principal components analysis, Tikhonov-regularized logistic classification, and least angle regression feature selection to predict remission by the end of the 12-week trial. We utilized ten-fold cross-validation and Receiver Operator Curves (ROC) curve analysis. To determine task-region pairs that significantly contributed to the algorithm's ability to predict remission, we used permutation testing. Using the fMRI data at both baseline and after the first dose of treatment yielded a sensitivity of 72% and a specificity of 68% (AUC = 0.77), a 15% increase in accuracy over baseline MADRS. In general, the accuracy at baseline was further improved by using the change in activation following a single dose. Activation of the frontal cortex, hippocampus, parahippocampus, caudate, thalamus, medial temporal cortex, middle cingulate, and visual cortex predicted treatment remission. Acute, dynamic trajectories of functional imaging metrics in response to a pharmacological intervention are a valuable tool for predicting treatment response in late-life depression and elucidating the mechanism of pharmacological therapies in the context of the brain's functional architecture.

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Neural activation changes after a single dose of antidepressants have been observed.

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Patients with late-life depression were treated with an antidepressant for 12 weeks.

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Neuroimaging data was recorded pre-treatment and after a single dose.

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Pre-treatment neuroimaging predicted remission at the end of the trial.

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Neuroimaging after a single dose improved prediction and may guide treatment.

Bone Turnover with Venlafaxine Treatment in Older Adults with Depression

OBJECTIVES

Epidemiologic data suggest older adults receiving serotonergic antidepressants may have accelerated bone loss. We examined bone turnover marker changes and patient-level variables associated with these changes in older adults receiving protocolized antidepressant treatment.

DESIGN

Open-label, protocolized treatment study.

SETTING

Medical centers in Pittsburgh, St Louis, and Toronto.

PARTICIPANTS

Older adults with major depression (N = 168).

MEASUREMENTS

Serum levels of the bone resorption marker C-terminal cross-linking telopeptide of type 1 collagen (CTX) and the bone formation marker procollagen type 1 N propeptide (P1NP) were assayed before and after 12 weeks of treatment with venlafaxine. Whether CTX and P1NP changes were associated with depression remission and duration of depression and genetic polymorphisms in the serotonin transporter (5HTTLPR) and 1B receptor (HTR1B) were also examined.

RESULTS

CTX increased and P1NP decreased during venlafaxine treatment, a profile consistent with accelerated bone loss. Two individual-level clinical variables were correlated with bone turnover; participants whose depression did not go into remission had higher CTX levels, and those with chronic depression had lower P1NP levels. HTR1B genotype predicted P1NP change, whereas 5HTTLPR genotype was unrelated to either biomarker.

CONCLUSION

Bone turnover markers change with antidepressant treatment in a pattern that suggests accelerated bone loss, although the clinical significance of these changes is unclear. These data are preliminary and argue for a larger, controlled study to confirm whether antidepressants are harmful to bone metabolism and whether certain individuals might be at increased risk.

Aging and Clinical Pharmacology: Implications for Antidepressants

The elderly frequently have changes in pharmacokinetics, sensitivity to medications, homeostatic reserve (ability to tolerate physiological challenges), exposure to multiple medications, and adherence. All of these age-associated factors can potentially influence total exposure to medication, adverse effects, and subsequent treatment outcome. Most clinical trials are performed with healthy, younger adults. Extrapolating the results of these trials to the elderly may be inappropriate, particularly for the antidepressant treatment of depression. The authors review these age-associated differences and discuss their implications for antidepressant use in older adults.

Use of antidepressant serotoninergic medications and cardiac valvulopathy: a nested case-control study in the health improvement network (THIN) database

AIMS

To quantify the risk of cardiac valvulopathy (CV) associated with the use of antidepressant serotoninergic medications (SMs).

METHODS

We conducted a case-control study nested in a cohort of users of antidepressant SMs selected from The Health Improvement Network database. Patients who experienced a CV event during follow-up were cases. Cases were ascertained in a random sample of them. Up to 10 controls were matched to each case by sex, age, month and year of the study entry. Use of antidepressant SMs during follow-up was defined as current (the last prescription for antidepressant SMs occurred in the 2 months before the CV event), recent (in the 2-12 months before the CV event) and past (>12 months before the CV event). We fitted a conditional regression model to estimate the association between use of antidepressant SMs and the risk of CV by means of odds ratios (ORs) and corresponding 95% confidence intervals (CIs). Sensitivity analyses were conducted to test the robustness of our results.

RESULTS

The study cohort included 752,945 subjects aged 18-89 years. Throughout follow-up, 1663 cases (incidence rate: 3.4 per 10,000 person-years) of CV were detected and were matched to 16,566 controls. The adjusted OR (95% CI) for current and recent users compared with past users of antidepressant SMs were 1.16 (0.96-1.40) and 1.06 (0.93-1.22), respectively. Consistent effect estimates were obtained when considering cumulative exposure to antidepressant SMs during follow-up.

CONCLUSIONS

These results would suggest that exposure to antidepressant SMs is not associated with an increased risk of CV.

Behavioral genetics of neurodegenerative disorders

Alzheimer's disease (AD) is the most common cause of dementia in the elderly, and is typically characterized by memory loss. In addition, during the disease progression, most patients develop behavioural and psychiatric symptoms of dementia (BPSD). Frontotemporal Lobar Degeneration (FTLD) is the most frequent neurodegenerative disorder with a presenile onset. It is characterized mainly by behavioural disturbances, whereas memory is conserved. The two major neuropathologic hallmarks of AD are extracellular Amyloid beta (Ab) plaques and intracellular neurofibrillary tangles (NFTs). Conversely, in FTLD the deposition of tau has been observed in a number of cases, but in several brains there is no deposition of tau but instead a positivity for ubiquitin. In some families these diseases are inherited in an autosomal dominant fashion. Genes responsible for familial AD include the Amyloid Precursor Protein (b-APP), Presenilin 1 (PS1)and Presenilin 2 (PS2). The majority of mutations in these genes are often associated with a very early onset (40–50 years of age). Regarding FTLD, the first mutations described are located in the Microtubule Associated Protein Tau gene(MAPT). Tau is a component of microtubules, which represent the internal support structures for the transport of nutrients, vesicles, mitochondria and chromosomes within the cell. Mutations in MAPT are associated with an early onset of the disease (40–50 years), and the clinical phenotype is consistent with Frontotemporal Dementia (FTD). Recently, mutations in a second gene, named progranulin(GRN), have been identified in some families with FTLD. The pathology associated with these mutations is most frequently characterized by the immunostaining of TAR DNA Binding Protein 43 (TDP-43), which is a transcription factor. The clinical phenotype associated with GRN mutations is highly heterogeneous,including FTD, Progressive Aphasia, Corticobasal Syndrome, and AD. Age at disease onset is variable, ranging from 45 to 85 years of age. The majority of cases of AD and FTLD are however sporadic, and likely several genetic and environmental factors contribute to their development. Concerning AD, it is known that the presence of the e4 allele of the Apolipoprotein E gene is a susceptibility factor,increasing the risk of about 4 fold. A number of additional genetic factors,including cytokines, chemokines, Nitric Oxide Synthases, contribute to the susceptibility for the disease. Some of them also influence the risk to develop FTLD.Variability in serotonin transporter gene could influence the development of BPSD. In this chapter, current knowledge on molecular mechanisms at the basis of AD and FTLD, as well as the role of genetics, will be presented and discussed.

Estradiol and progesterone modify the effects of the serotonin reuptake transporter polymorphism on serotonergic responsivity to citalopram

Individual vulnerability to psychopathologies is linked to a number of genetic polymorphisms including the serotonin transporter (5HTT) promoter polymorphic region (5HTTLPR). A single copy of the short variant (s-variant) allele of 5HTTLPR confers increased susceptibility to anxiety disorders and depression and decreased efficacy of serotonin-releasing agents in pharmacotherapy compared to the homozygous long 5HTTLPR variant (l/L). The data suggesting that the 5HTTLPR polymorphism modulates the efficacy of serotonin-releasing agents in pharmacotherapy is inconsistent. Other factors such as age, gender, and hormonal status could interact with 5HTTLPR genotype to affect individual physiological and behavioral responses to serotonin reuptake inhibitors such as citalopram. Indeed, estradiol and progesterone, the primary female steroid hormones, exert an array of effects on the serotonergic system, including 5HTT expression. The present study used ovariectomized female rhesus monkeys to determine the interaction between the 5HTTLPR polymorphism and the effects of midfollicular levels of estradiol and luteal levels of progesterone on serotonergic responsivity to acute citalopram administration. The increase in serum prolactin, a surrogate measure of serotonin activity, following citalopram administration was significantly larger in l/L females than in s-variant females over the course of two hours during concurrent estradiol and progesterone hormone replacement only. These data suggest that ovarian function and the 5HTTLPR polymorphism interact to gate serotonergic reactivity in females, suggesting that clinicians should be aware of the ovarian status and 5HTTLPR genotype of women when considering serotonergic pharmacotherapy in women.

Relation of serotonin transporter genetic variation to efficacy of escitalopram for generalized anxiety disorder in older adults

OBJECTIVE

Generalized anxiety disorder (GAD) is common in older adults and can be treated with selective serotonin reuptake inhibitors (SSRIs). Genetic variation in the serotonin transporter gene promoter region is posited to be associated with SSRI efficacy: 2 polymorphisms (5-HTTLPR S/L and rs25531 g/a) form a haplotype with the La combination having higher transcription activity than other haplotypes. We hypothesized that GAD patients with no La haplotypes (La⁻) have lower SSRI treatment efficacy than those with 1 to 2 La haplotypes (La+).

METHOD

The study enrolled subjects aged 60 years or older with a principal diagnosis of GAD into a 12-week, randomized trial of escitalopram versus placebo. One hundred fifty subjects were genotyped for the serotonin transporter promoter region haplotype and were divided into La⁻ and La+ genotype groups; the primary analyses were done in European Americans only (n = 125; n = 59 with escitalopram and n = 66 with placebo).

RESULTS

Escitalopram had no efficacy in the La⁻ group versus moderate efficacy in the La+ group. This genetic moderation of SSRI efficacy was due to a higher placebo response in La⁻ subjects, compared with La+ subjects. Drug concentration did not affect the genetic results. Exploratory analyses suggest that La⁻ subjects had greater variability of anxiety symptoms unrelated to treatment.

CONCLUSIONS

The serotonin transporter promoter haplotype is associated with variability in SSRI efficacy for late-life GAD. The variability may result from a genetic effect on anxiety symptom variability unrelated to treatment, rather than a pharmacodynamic effect that has been previously assumed. Further research is needed to understand the pharmacogenetic mechanism of this haplotype.

Current developments and controversies: does the serotonin transporter gene-linked polymorphic region (5-HTTLPR) modulate the association between stress and depression?

PURPOSE OF REVIEW

Human observational studies have shown that, in interaction with life stress, the short or S-allele of the serotonin transporter gene-linked polymorphic region (5-HTTLPR) is associated with an enhanced risk for depression. However, this gene-by-environment interaction (G×E) has recently been questioned by two meta-analyses. We aim to provide an overview and appraisal of recent developments and controversies.

RECENT FINDINGS

The statistical approach of the meta-analyses aimed at a very strict replication of the initial finding and, accordingly, included only a minority of all available studies. Furthermore, the negative results of the meta-analyses appear to be predominantly driven by a few large studies that used retrospective, self-report measures of life stress. In contrast, among 19 studies using interview-based or more objective measures of stress, there were 13 replications, five part-replications and only one nonreplication. Finally, a broader approach based on evidence from different research fields and methodologies supports a 5-HTTLPR by stress interaction.

SUMMARY

Whereas there is no doubt that the meta-analyses are methodologically sound, it appears that this technique is only in part suitable for appraising all of the available evidence. Furthermore, convergent evidence is accumulating from different research fields that 5-HTTLPR is indeed closely associated with different biological pathways associated with stress regulation and depression.

Linking the cytokine and neurocircuitry hypotheses of depression: a translational framework for discovery and development of novel anti-depressants

Recent studies suggest a model of depression that links the cytokine hypothesis from the field of psychoneuroimmunology with the neurocircuitry hypothesis derived from burgeoning insight into neurophysiological changes observed in depressed patients. According to the neurocircuitry hypothesis of depression, failure of homeostatic synaptic plasticity in cortical-striatal-limbic nodes of a distributed network of neural circuits involving the sub-genual anterior cingulate cortex is responsible for core symptoms of depression: loss of interest or pleasure (anhedonia) and depressed mood (sadness). According to the cytokine hypothesis of depression, inflammatory cytokines act on neural circuits to evoke the behavioral and physiological changes observed in depression. Synthesis of these hypotheses implicates cytokines released during injury, infection, illness, or psychological stress as a cause of dysregulated synaptic plasticity in cortical-striatal-limbic circuits implicated in depression. These neural circuits process affective and reward-based information for optimal cost-benefit decision-making, a function that may link cytokine-evoked changes in synaptic plasticity to translatable measures of specific behavioral impairments observed in depressed patients. This viewpoint outlines evidence linking the cytokine and neurocircuitry hypotheses of depression to offer a translational model of major depressive disorder suitable for novel drug discovery and development.

The intersection of pharmacology, imaging, and genetics in the development of personalized medicine

We currently rely on large randomized trials and meta-analyses to make clinical decisions; this places us at a risk of discarding subgroup or individually specific treatment options owing to their failure to prove efficacious across entire populations. There is a new era emerging in personalized medicine that will focus on individual differences that are not evident phenomenologically. Much research is directed towards identifying genes, endophenotypes, and biomarkers of disease that will facilitate diagnosis and predict treatment outcome. We are at the threshold of being able to predict treatment response, primarily through genetics and neuroimaging. In this review we discuss the most promising markers of treatment response and adverse effects emerging from the areas of pharmacogenetics and neuroimaging in depression and schizophrenia.

Sex-specific association between the 5-HTT gene-linked polymorphic region and basal cortisol secretion

OBJECTIVE

A key regulator of serotonergic neurotransmission is the serotonin transporter (5-HTT) and a common 5HTT gene promoter polymorphism, termed 5HTTLPR, is associated with phenotypes related to anxiety and depression. Furthermore, the serotonergic system influences hypothalamus-pituitary-adrenal (HPA) axis activity, which, in turn, is related to psychiatric diseases.

METHODS

To explore the association between the 5-HTTLPR and HPA axis regulation we performed a detailed endophenotyping in 216 healthy subjects (all 126 females used oral contraceptives).

RESULTS

While ACTH and cortisol responses to an established psychosocial stress paradigm (Trier Social Stress Test) were not found to be related to the 5-HTTLPR, we observed a significant and sex-specific association with the cortisol awakening response, which is a reliable marker of basal cortisol secretion, and with ACTH levels after dexamethasone administration. The supplementary inclusion of a 5-HTT A/G polymorphism (rs25531) in the analyses did not substantially modify our results.

CONCLUSION

These findings support the view that the 5-HTTLPR is associated with a major neuroendocrine stress system. It could be speculated that the sex-specific nature of this association contributes to the distinct gender differences in the vulnerability for depression.

Treatment resistant depression as a failure of brain homeostatic mechanisms: implications for deep brain stimulation

Given the profound negative public health effects of major depressive disorder (MDD), and data suggesting only modest effectiveness of existing psychological and pharmacological treatments for this condition, there has been increasing interest in exploring the antidepressant potential of non-pharmacological, brain-based interventions, such as deep brain stimulation (DBS). The use of the DBS for psychiatric indications follows a decade of data suggesting that DBS is an effective, evidence-based strategy for the treatment of movement disorders such as Parkinson's disease. At the present time there is open-label case series data to suggest that DBS in the subgenual cingulate gyrus, ventral caudate/ventral striatum, and the nucleus accumbens, is associated with antidepressant effects in individuals who fail to respond to conventional treatments for MDD. However a number of unresolved issues about the optimal use of DBS for MDD remain, such as the optimal anatomical placement of the electrodes and the mechanisms of its antidepressant effects. This review summarizes the clinical experience of DBS for treatment resistant depression (TRD). The rationale for the use of DBS for TRD is reviewed in the context of the growing neuroimaging literatures exploring the biomarkers of antidepressant response, and the neural substrates of emotional regulation in both normal and pathological states.

Psychological vulnerability differences in students--carriers or not of the serotonin transporter promoter allele S: effect of adverse experiences

AIM

To study the effect of the serotonin transporting gene L/S polymorphism on several psychological characteristics in a group of Greek University students.

METHODS

One hundred eighty-one students were genotyped and classified into two groups: carriers or noncarriers of an S allele. Students were evaluated with a battery of psychological tests (Zung depression rating scale, symptoms check-list-90-R, Eysenck personality inventory); they also answered questionnaires regarding serious past adverse experiences as well as nicotine and alcohol use. Multivariate analysis of variance (MANOVA) was used to check the main effect of genotype and its interaction with both adverse life experiences and scores of psychological tests.

RESULTS

No significant differences were detected between the two groups of students regarding scores of the psychological tests. Yet, analysis with MANOVA indicated an interaction between genotype and adversities (lambda = 0.838, F(17,158) = 1.802, P = 0.032). Students who both carry at least one S allele and have faced serious past adverse life experiences have scored higher than carriers of the S allele who have not faced adversities on the following: global severity index (F(1174) = 5.973, P = 0.016), positive symptoms distress index (F(1174) = 4.518, P = 0.035), somatization (F(1174) = 4.074, P = 0.045), depression (F(1174) = 4.971, P = 0.027), anxiety (F(1174) = 8.112, P = 0.005), phobic anxiety (F(1174) = 16.421, P < 0.000), and paranoid ideation (F(1174) = 5.143, P = 0.025). Among students without adversities, those with the LL genotype have scored higher than S allele carriers on the following: depression (t = 2.680, df = 75, P = 0.009), anxiety (t = 2.629, df = 75, P = 0.010), phobic anxiety (t = 3.350, df = 75, P = 0.001), and paranoid ideation (t = 2.668, df = 75, P = 0.009).

CONCLUSION

The S and L alleles seem to interact differently with serious past life adversities in influencing psychological vulnerability. Adversities seem to have a stronger effect on S carriers. LL genotype might be related to the expression of certain more endogenous psychopathological tendencies.

Pharmacogenetics and the serotonin transporter in late-life depression

BACKGROUND

The etiologies of variable antidepressant response remain elusive. Aging and age-related illness add to the complexity and heterogeneity of late-life depression. The serotonin transporter (5-HTT) is the principal site of initial action for several antidepressants, including serotonin re-uptake inhibitors (SSRIs). The serotonin transporter-linked polymorphic region (5-HTTLPR) is the most widely studied polymorphism of the 5-HTT gene, SLC6A4, and is suspected of conferring vulnerability to elderly depression and resistance to treatment.

OBJECTIVE

To present an up-to-date account of the influence of 5-HTT polymorphisms on elderly depression, antidepressant response and susceptibility to medication side effects.

METHOD

A Medline search (1993 - 2008) of 5-HTT gene variation studies and analyses that included elderly depressed subjects was performed using the terms: 'serotonin transporter'; '5-HTT'; 'SERT'; '5-HTTLPR'; 'late-life depression'; 'elderly depression'; 'geriatric depression'; 'antidepressants' and 'SSRIs'. Reference sections were gleaned for relevant articles that may have been overlooked by the search strategy.

CONCLUSION

5-HTTLPR may influence treatment response variability in late-life depression in a number of ways. Indirectly, 5-HTTLPR seems to influence the likelihood of adverse effects and non-adherence. Directly, the promoter region may contribute to response variability during the initial stages of treatment, which is explained, in part, by a gene-concentration interaction for paroxetine. Subjects with the S allele may be at an increased risk of adverse drug reactions and may require higher initial SSRI plasma concentrations to maximize response. Conversely, patients with the L/L genotype may respond even at lower concentrations.

Incomplete response in late-life depression: getting to remission

Incomplete response in the treatmen tof late-life depression is a large public health challenge: at least 50% of older people fail to respond adequately to first-line antidepressant pharmacotherapy, even under optimal treatment conditions. Treatment-resistant late-life depression (TRLLD) increases risk for early relapse, undermines adherence to treatment for coexisting medical disorders, amplifies disability and cognitive impairment, imposes greater burden on family caregivers, and increases the risk for early mortality, including suicide, Gettinq to and sustaininq remission is the primary goal of treatment yet there is a paucity of empirical data on how best to manage TRLLD. A pilot study by our group on aripiprazole augmentation in 24 incomplete responders to sequential SSRI and SRNI pharmacotherapy found that 50% remitted over 12 weeks with the addition of aripiprazole, and that remission was sustained in all participants during 6 months of continuation treatment In addition to controlled assessment, evidence is needed to support personalized treatment by testing the moderating role of clinical (eg, comorbid anxiety, medical burden, and executive impairment) and genetic (eg, selected polymorphisms in serotonin, norepinephrine, and dopamine genes) variables, while also controlling for variability in drug exposure. Such studies may advance us toward the goal of personalized treatment in late-life depression.

The influence of 5-HTTLPR and STin2 polymorphisms in the serotonin transporter gene on treatment effect of selective serotonin reuptake inhibitors in depressive patients

BACKGROUND

Serotonin transporter gene (SLC6A4) variations have been proposed as an explanation for interindividual differences in selective serotonin reuptake inhibitors (SSRIs) effects. Quantitative assessment of genetic influences is necessary to evaluate whether genetic testing before antidepressant prescription would lead to earlier treatment effects. This study evaluates the influence of two polymorphisms (5-HTTLPR and STin2) on SSRI treatment outcome in depression.

METHODS

We included 50 SSRI nonresponders (cases) and 164 referents meeting Diagnostic and Statistical Manual Of Mental Disorder-IV criteria for major depression and using an SSRI for at least 6 weeks. Blood samples or buccal swabs were gathered to determine 5-HTTLPR (N=48 for cases and 161 for referents) and STin2 (N=50 for cases and 162 for referents) genotypes. The association between genotype and SSRI response was assessed by use of logistic regression.

RESULTS

Patients with the 5-HTTLPR s-allele had a nonsignificantly increased risk of SSRI nonresponse; odds ratio (OR) 1.60, 95% confidence interval (CI) 0.66-3.89. 5-HTTLPR effects were strongest in female patients (OR 3.54, 95% CI 1.05-11.92), and for male patients 5-HTTLPR seemed to have no effect (OR 0.29, 95% CI 0.04-2.34). An age-dependent effect of 5-HTTLPR was observed; patients under 44 years of age had an increased nonresponse risk (OR 9.34, 95% CI 1.41-61.98). STin2 genotype had no clear influence on treatment outcome.

CONCLUSION

Our findings indicate that women with the 5-HTTLPR s-allele have a less favorable response to SSRI treatment. To our knowledge, this is the first time that a gender-dependent influence of 5-HTTLPR is reported. More research is needed, particularly in subgroups of patients, before implementation of genetic testing can be recommended.

Empirically derived decision trees for the treatment of late-life depression

OBJECTIVE

Several predictors of treatment response in late-life depression have been reported in the literature. The aim of this analysis was to develop a clinically useful algorithm that would allow clinicians to predict which patients will likely respond to treatment and thereby guide clinical decision making.

METHOD

A total of 461 patients with late-life depression were treated under structured conditions for up to 12 weeks and assessed weekly with the 17-item Hamilton Rating Scale for Depression (HAM-D-17). The authors developed a hierarchy of predictors of treatment response using signal-detection theory. The authors developed two models, one minimizing false predictions of future response and one minimizing false predictions of future nonresponse, to offer clinicians two clinically useful treatment algorithms.

RESULTS

In the first model, early symptom improvement (defined by the relative change in HAM-D-17 total score from baseline to week 4), lower baseline anxiety, and an older age of onset predict response at 12 weeks. In the second model, early symptom improvement represents the principal guide in tailoring treatment, followed by baseline anxiety level, baseline sleep disturbance, and--for a minority of patients--the adequacy of previous antidepressant treatment.

CONCLUSIONS

Our two models, developed to help clinicians in different clinical circumstances, illustrate the possibility of tailoring the treatment of late-life depression based on clinical characteristics and confirm the importance of early observed changes in clinical status.

Haplotype analysis confirms association of the serotonin transporter (5-HTT) gene with schizophrenia but not with major depression

Serotonin (5-HT) has been implicated in the pathophysiology of several psychiatric disorders including major depressive disorder (MDD) and schizophrenia (SCZ). The serotonin transporter (5-HTT) is a major regulator of 5-HT function. 5-HTT gene polymorphic variants have been associated with both MDD and SCZ. A case-control design was used for candidate gene-disease association in 194 MDD patients, 155 schizophrenic psychosis patients, and 246 healthy controls, all North European Caucasians. Four polymorphisms were analyzed in terms of genotype, allele, and haplotype-based associations. Linkage disequilibrium (LD) analysis was also carried out. Bonferroni correction was used for multiple testing. Haplotype-based analyses showed significant associations between 5-HTT and SCZ but not MDD. No single locus associations were observed. In agreement with published meta-analysis our results indicate that 5-HTT associates with SCZ but not with MDD. It appears that risk for SCZ maps within a specific 5-HTT haplotype block.

The effects of the dopamine and serotonin transporter polymorphisms on clinical features and treatment response in geriatric depression: a pilot study

BACKGROUND

The authors examined the role of dopamine and serotonin transporter genetic polymorphisms in clinical and cognitive features of subjects with late-life depression, and in preferential treatment response to the combination of methylphenidate and citalopram.

METHOD

The authors studied fifteen outpatients with major depression in a pilot ten-week double-blind trial of methylphenidate combined with citalopram and compared to citalopram and placebo. Response was defined as a score on the Hamilton Depression Rating Scale (24-item) of less than 10. All underwent genotyping to determine the dopamine (DAT VNTR) and serotonin (5HTTLPR) transporter polymorphisms.

RESULTS

Subjects with DAT VNTR 10/10 genotype had greater cognitive executive dysfunction at baseline compared to others. However, they responded preferentially to methylphenidate added to citalopram with a greater reduction in depression severity over time compared to other subjects.

CONCLUSIONS

DAT VNTR 10/10 genotype may be associated with an endophenotype of late-life depression with executive dysfunction that responds preferentially to methylphenidate added to a selective serotonin reuptake inhibitor, which warrants replication in a large sample.

Predicting 6-week treatment response to escitalopram pharmacotherapy in late-life major depressive disorder

OBJECTIVE

Approximately half of older patients treated for major depressive disorder (MDD) do not achieve symptomatic remission and functional recovery with first-line pharmacotherapy. This study aims to characterize sociodemographic, clinical, and neuropsychologic correlates of full, partial, and non-response to escitalopram monotherapy of unipolar MDD in later life.

METHODS

One hundred and seventy-five patients aged 60 and older were assessed at baseline on demographic variables, depression severity, hopelessness, anxiety, cognitive functioning, co-existing medical illness burden, social support, and quality of life (disability). Subjects received 10 mg/d of open-label escitalopram and were divided into full (n = 55; 31%), partial (n = 75; 42.9%), and non-responder (n = 45; 25.7%) groups based on Hamilton depression scores at week 6. Univariate followed by multivariate analyses tested for differences between the three groups.

RESULTS

Non-responders to treatment were found to be more severely depressed and anxious at baseline than both full and partial responders, more disabled, and with lower self-esteem than full responders. In general partial responders resembled full responders more than they resembled non-responders. In multivariate models, more severe anxiety symptoms (both psychological and somatic) and lower self-esteem predicted worse response status at 6 weeks.

CONCLUSION

Among treatment-seeking elderly persons with MDD, higher anxiety symptoms and lower self-esteem predict poorer response after six weeks of escitalopram treatment.

Increased risk for major depression associated with the short allele of the serotonin transporter promoter region (5-HTTLPR-S) and the CYP2C9*3 allele

In the present study, we aimed to analyze the potential relevance of the polymorphism in the promoter region of the serotonin transporter (SERT or 5-HTT) gene (5-HTTLPR) and the risk of suffering major depression (MDD) in a population of patients previously genotyped for CYP2C9. Seventy white European psychiatric outpatients suffering from MDD and a group of 142 healthy volunteers (HVs) were studied. The frequency of subjects carrying the 5-HTTLPR-S allele was higher (P < 0.05) among MDD than in HV. The odds ratio associated with 5-HTTLPR-S allele was 2.03 for the MDD patients in comparison with the HV group. Previously, we found in this population that the CYP2C9*3 allele frequency was higher among this population of MDD patients than in HV. The frequency of subjects with the combination 5-HTTLPR-S and CYP2C9*3 alleles was higher (P < 0.01, odds ratio 3.47) in MDD than in HV. The present findings provide preliminary evidence about the greater risk of suffering MDD for individuals carrying both 5-HTTLPR-S and CYP2C9*3 alleles.

Does pretreatment testing for serotonin transporter polymorphisms lead to earlier effects of drug treatment in patients with major depression? A decision-analytic model

BACKGROUND

An estimated 30% to 40% of patients with depression do not sufficiently respond to treatment with selective serotonin reuptake inhibitors (SSRIs) and the period in which treatment efficacy can be assessed is relatively long. Therefore, a test to identify potential nonresponders could be useful in the treatment of depression. Serotonin transporter gene (SLC6A4) variations have been reported to account for differences in the way individuals respond to SSRI treatment.

OBJECTIVE

A decision-analytic model was used to assess whether pretreatment genetic testing for 5-HTTLPR, a polymorphism of the SLC6A4 genotype, could be an efficient tool in the treatment of depression.

METHODS

A theoretical clinical decision-analytic model was constructed to compare the current treatment strategy in The Netherlands with an alternative strategy for the treatment of depression. Under treatment guidelines in The Netherlands, all patients with depression receive SSRI treatment (nontesting strategy). Under the alternative strategy, genetic testing would be performed to identify which class of antidepressant would be the best choice for initiation of treatment (genetic testing strategy). Probabilities (predicted results) for this model were based on data from previous studies and the opinions of experts in the field of psychopharmacology. To test the robustness of the model, 6- and 12-week remission rates for patients treated with SSRIs were varied in a sensitivity analysis using a predetermined range that was established based on expert opinion. Threshold analyses were performed on the parameters of serotonin transporter genotype frequency and response and nonresponse rates for patients receiving SSRIs, serotonin-norepinephrine reuptake inhibitors (SNRIs), and tricyclic antidepressants (TCAs) to determine the value for a variable at which it could be concluded that a change in treatment strategy would be preferred.

RESULTS

When genetic testing was performed before an antidepressant was prescribed, 64.6% of patients were predicted to be in remission after 6 weeks of treatment compared with 60.0% of patients who did not receive genetic testing. After 12 weeks, 79.5% of patients in the testing group who received an SNRI as initial treatment and 83.2% of those who received a TCA initially were predicted to be in remission compared with 76.7% of patients in the nontesting group. Sensitivity analyses indicated that the model was robust to variation of probability estimates within their plausible ranges. However, these findings were based on a theoretic model and did not include cost assessment. Pretreatment genetic testing must be evaluated further in randomized clinical trials and costs must be assessed before implementing this strategy in routine psychiatric practice can be recommended.

CONCLUSIONS

The findings of this study suggest that performing genetic testing before prescribing antidepressant treatment may lead to greater numbers of patients experiencing remission early in treatment.

Serotonin transporter polymorphisms and the occurrence of adverse events during treatment with selective serotonin reuptake inhibitors

During treatment with selective serotonin reuptake inhibitors, some patients experience adverse events whereas others do not. Assessment of predictors for selective serotonin reuptake inhibitors-induced adverse events would be useful for the identification of patients likely to develop these events. This study evaluates the association between adverse events during selective serotonin reuptake inhibitor treatment and two polymorphisms in the serotonin transporter (5-HTTLPR and STin2) gene. We included 214 patients meeting Diagnostic and statistical manual of mental disorder-IV criteria for major depression and using an selective serotonin reuptake inhibitor for at least 6 weeks. Blood samples or buccal swabs were taken to determine 5-HTTLPR and STin2 genotype. Information on adverse events was gathered through interviews and general practitioners' files. The association between serotonin transporter genotype and adverse events was assessed by use of logistic regression. Patients with the 5-HTTLPR s/s or s/l genotype appeared to have an increased risk of adverse events, especially general adverse events (dermatologic reactions, weight change and fatigue); odds ratio 1.77 (95% confidence interval 0.80-3.92) for the s/s genotype, odds ratio 2.37 (95% confidence interval 1.13-4.96) for the s/l genotype. For STin2, results were inconsistent and observed associations were weak and statistically nonsignificant. Our findings indicate that patients with the 5-HTTLPR s/s or s/l genotype have an increased risk of developing adverse events during selective serotonin reuptake inhibitor treatment.

Strain differences in ‘compulsive’ lever-pressing

In the signal attenuation rat model of obsessive-compulsive disorder, 'compulsive' behavior is induced by attenuating a signal indicating that a lever-press response was effective in producing food. In recent years several studies have reported that Lewis rats, an inbred strain derived from the Sprague Dawley strain, exhibit addictive and/or compulsive tendencies. The aim of the present study was thus to test whether Lewis rats will also show increased compulsivity in the signal attenuation model. Because the model has been developed and validated using Wistar rats only, the present study compared the behavioral response to signal attenuation of Lewis, Sprague Dawley and Wistar rats, and assessed the effects of the anti-compulsive drug paroxetine on compulsive behavior in Lewis and Sprague Dawley rats. The results show that Lewis rats are more 'compulsive' than Sprague Dawley and Wistar rats in terms of both higher levels of compulsive lever-pressing and higher resistance to the anti-compulsive effect of paroxetine. The possibility that these strain differences are related to strain differences in the serotonergic and dopaminergic systems are discussed in light of current knowledge of the pathophysiology and pharmacotherapy of OCD.

Serotonin transporter gene influences the time course of improvement of "core" depressive and somatic anxiety symptoms during treatment with SSRIs for recurrent mood disorders

The short variant of the serotonin transporter gene (SERTPR) has been consistently associated with a poorer response to treatment with various selective serotonin reuptake inhibitors (SSRIs). Antidepressant response is not a unitary phenomenon, however, and we here hypothesized that the SERTPR effect could be specific to some types of symptomatology. The sample comprised 281 inpatients affected by mood disorders and treated for major depression with SSRIs. The total depressive scores for all patients were analyzed in previous reports, but symptomatologic clusters were not examined previously. The 21-item Hamilton Rating Scale for Depression (HAM-D) was administered to evaluate depressive symptoms at baseline and weekly over 6 weeks of treatment. All patients were genotyped for the SERTPR polymorphism. Compared with patients with the SERTPR l/l and l/s polymorphisms, s/s patients showed a selective and slower improvement of depressive "core" and somatic anxiety symptoms, but they did not differ from other patients regarding other symptomatologic clusters such as insomnia and motor retardation. These findings support the view that response to SSRIs is not a unitary phenomenon and that improvement of symptomatologic clusters as, at least in part, genetically driven. SERTPR may be hypothesized as concurrently participating to the activity of anatomic brain regions differentially involved in depression and somatic symptoms of anxiety; however, further studies are required to examine these complex interactions.

Links between depression and substance abuse in adolescents: neurobiological mechanisms

Adolescence is a high-risk period for development of both depressive and substance use disorders. These two disorders frequently co-occur in adolescents and are associated with significant morbidity and mortality. Given the added economic and psychosocial burden associated with the comorbid condition, identification of risk factors associated with their co-occurrence is of great public health importance. Research with adult animals and humans has indicated several common neurobiological systems that link depressive and addictive disorders. Given the ongoing maturation of these systems throughout adolescence and early adult life, it is not clear how these neurobiological processes influence development and progression of both disorders. A better understanding of the pathophysiological mechanisms leading to the onset and course of these disorders during adolescence will be helpful in developing more effective preventive and treatment strategies, and thereby allow these youth to reach their full potential as adults.

Serotonin transporter linked promoter (polymorphism) in the serotonin transporter gene may be associated with antidepressant-induced mania in bipolar disorder

OBJECTIVE

Several pharmacogenetic studies suggest that response to pharmacotherapy in bipolar disorder may be mediated by genetic factors. The aim of this study was to investigate further the association of the genetic variations of the serotonin transporter (5-HTT) gene with antidepressant-induced mania, already reported in recent studies. We also studied the possible association of these genetic variants with diagnosis expression and treatment response to lithium therapy.

METHODS

The sample consisted of 103 and 85 outpatients with diagnosis of bipolar and unipolar disorder, respectively, and 101 controls. Two described polymorphisms of the 5-HTT, the variable number of tandem repeat (VNTR) and serotonin transporter linked promoter (5-HTTLPR) polymorphisms, were genotyped using standard procedures.

RESULTS

The association analysis performed showed a significantly higher rate of homozygous s/s genotype for 5-HTTLPR among patients with a history of antidepressant-induced mania (60% patients s/s versus 40% l/l, chi, P=0.04). No significant difference in the distribution of genotypes of the two polymorphisms was observed between the three groups. We found no significant association between these polymorphisms and lithium response.

CONCLUSIONS

The 5-HTTLPR polymorphism could be a useful contributor, among other clinical variables, to predict the risk for manic switches when a patient with bipolar disorder is treated with antidepressant drugs. The contribution of these genetic markers in diagnosis expression and treatment response to lithium is likely to be minor.

The future of selective serotonin reuptake inhibitors (SSRIs) in psychiatric treatment

Selective serotonin reuptake inhibitors (SSRIs) are widely prescribed and widely regarded as a first-line treatment for depression. Yet, a growing body of evidence indicates that these agents are only moderately more effective than placebo in treating major depressive disorder. In recent years, it has been debated whether SSRIs offer any clinically meaningful advantage over placebos. As part of this debate, it has been argued that these agents are first-line treatments for some forms of depression but not necessarily for others. The present paper examines two hypotheses that are central to these issues. The first hypothesis is that SSRIs are more effective than placebo for some types of depression but not for others. The second is that SSRIs are more effective than psychotherapies for some types of depression than others. A review of the empirical literature reveals three main classifications of depression that are relevant to the first hypothesis: (a) more vs. less severe depression, (b) melancholic vs. non-melancholic depression, and (c) depression defined according to associated genetic factors (particularly the long vs. short allele of the serotonin transporter gene promoter). There is no strong or consistent support for (a) or (b). There is, however, emerging and consistent evidence for (c), and so the first hypothesis is tentatively supported, but only for (c). Most of the empirical evidence does not support the second hypothesis. Psychotherapies (cognitive-behavioral and interpersonal therapies) and SSRIs generally have equivalent efficacy, regardless of the severity of depression. The research literature also suggests a third hypothesis that remains to be evaluated: that SSRIs are more effective for treating anxiety disorders (and possibly other disorders) than they are for treating depression. If that hypothesis is supported by subsequent research, then the future of SSRIs may lie largely in the treatment of anxiety disorders, and in the management of particular subtypes of depression.

The pharmacokinetic imperative in late-life depression

Older patients frequently have a high burden of medical illness, are subject to extensive medication regimens, and often experience adverse drug events. In general, pharmacokinetic changes associated with aging result in higher and more variable drug concentrations in older patients. Nonetheless, available information on pharmacokinetics of antidepressants is inadequate particularly with regard to medical subgroups and potential drug interactions. Although age-associated pharmacodynamic changes appear to make older patients more sensitive to side effects of antidepressants, differences in pharmacodynamics are not interpretable in the absence of drug concentration data. Population pharmacokinetics provides a means for assessing antidepressant drug exposure with relative ease and precision in clinical trials.

Candidate genes for antidepressant response to selective serotonin reuptake inhibitors

Selective serotonin reuptake inhibitors (SSRIs) can safely and successfully treat major depression, although a substantial number of patients benefit only partially or not at all from treatment. Genetic polymorphisms may play a major role in determining the response to SSRI treatment. Nonetheless, it is likely that efficacy is determined by multiple genes, with individual genetic polymorphisms having a limited effect size. Initial studies have identified the promoter polymorphism in the gene coding for the serotonin reuptake transporter as moderating efficacy for several SSRIs. The goal of this review is to suggest additional plausible polymorphisms that may be involved in antidepressant efficacy. These include genes affecting intracellular transductional cascades; neuronal growth factors; stress-related hormones, such as corticotropin-releasing hormone and glucocorticoid receptors; ion channels and synaptic efficacy; and adaptations of monoaminergic pathways. Association analyses to examine these candidate genes may facilitate identification of patients for targeted alternative therapies. Determining which genes are involved may also assist in identifying future, novel treatments.

Allelic isoforms and decrease in serotonin transporter mRNA in lymphocytes of patients with major depression

Serotonin transporter, measured by the specific binding of [(3)H]paroxetine, has been reported to be reduced in circulating lymphocytes of patients with major depression. Due to this observation, the objective of the present report was to determine the levels of serotonin transporter mRNA in lymphocytes obtained from 29 major depression patients (4 men, age 33.10+/-1.63 years) and from 30 subjects included as a control group (4 men, age 37.54+/-2.18 years) using RT-PCR. The patients were diagnosed according to the criteria of the American Psychiatric Association, and had a severity of depression of 32.68+/-1.55 determined by the Hamilton Rating Scale for Depression. The DNA was submitted to polymerase chain reaction with primers for the 5' regulatory region of human serotonin transporter, which could show the long and the short allelic forms of the transporter gene for the 5 HTTLPR polymorphism. Semiquantitative analysis was performed using beta-actin as internal and external standard. Control subjects presented the two allelic forms in 9.09% and depressed patients in 8.69%. The long variant was present in 73% of controls and in 60% of patients, without significant differences. There was a significant reduction in mRNA in depressed patients expressing the long allele. The number of immunofluorescent lymphocytes, labeled with a specific antibody against serotonin transporter, was reduced in the patients, as well as CD3+ lymphocytes. Serotonin and 5-hydroxyindoleacetic acid in platelet-poor plasma or lymphocytes did not differ between depressed patients and controls. The reduction in lymphocyte serotonin transporter described in major depression might be due to a decrease in the level of its mRNA and in the number of cells expressing it. These observations might implicate that functional modifications are associated with nervous-immune interactions in depression.

Effects of serotonin transporter promoter polymorphisms on serotonin function

The serotonin transporter promoter polymorphism (5-HTTLPR) has been associated with vulnerability to stress-induced depressive symptoms and with the speed and rate of response to antidepressant treatment. The goal of the present study was to evaluate the association between the 5-HTTLPR and the functional response of the serotonin system as measured by the neuroendocrine and cerebral metabolic response to intravenous administration of the selective serotonin reuptake inhibitor citalopram in normal control subjects. Genotyping was performed for 5-HTTLPR insertion/deletion polymorphism long (l) and short (s) variant alleles. The ll genotype was compared with the combined sl+ss and with the ss genotype alone. Citalopram plasma concentrations did not differ significantly between groups. The s allele was associated with a less of an increase in prolactin and cortisol than the ll genotype. The s allele was associated with greater decreases in left frontal, precentral and middle temporal gyri compared to the ll genotype. The ll genotype was associated with greater decreases in right frontal, insula and superior temporal gyrus compared to the ss genotype. These findings suggest that 5-HTTLPR is associated with an altered functional response of the serotonin system, which may represent a neurobiologic substrate for the differential response to antidepressant treatment in late life and the emergence of neuropsychiatric symptoms in neurodegenerative disorders.

Meta-analysis of serotonin transporter polymorphisms and affective disorders

Polymorphisms in the promoter region (5-HTTLPR) of the serotonin transporter and a variable number of tandem repeats polymorphism in the second intron have been widely studied. However, the results of association studies examining unipolar depression (MDD) or bipolar disorder depression (BPD) have been mixed. To precisely ascertain small associations with both polymorphisms, a meta-analysis was performed involving several thousand subjects, using random-effects modeling. For MDD, the effect of the 5-HTTLPR genotype was significant (chi2=6.1, P<0.05), with 21% of MDD subjects and 17% of controls homozygous for the short (S) allele (odds ratio, 1.16). Similar findings were noted in BPD, with a higher frequency of S/S genotypes in affected patients, although the results did not reach statistical significance. Results of transmission disequilibrium tests trended in a similar direction but also did not reach statistical significance. No consistent effect of the variable number of tandem repeats polymorphism was revealed for either MDD or BPD. The results suggest that the S allele, or a neighboring allele in linkage disequilibrium, is recessive for MDD and possibly BPD. Notably, the association is very small. With these small associations, confounding issues such as population stratification require addressing. Significant heterogeneity between studies was also evident, possibly reflecting differences in diagnosis, different control populations, and different ethnic populations. These factors should Influence the interpretation of the association found in this analysis.

Eating disorders, serotonin transporter polymorphisms and potential treatment response

Anorexia nervosa, bulimia nervosa, and binge eating disorder are eating disorders with common clinical and psychological features, potentially shared mechanisms, significant morbidity and, at least for anorexia nervosa, a high mortality rate. Among the numerous risk factors involved, the importance of a genetic vulnerability has been demonstrated, and the heritability, in the broad sense, has being estimated to be between 50 and 70%. Studies have thus focused on different candidate genes. Serotonin transmission and regulation has been extensively studied with regard to its role in core mechanisms such as feeding and fasting, but also in different clinical characteristics of eating disorders. The serotonin transporter (5-HTT), encoded by the SLC6A4 gene, may also have an important role in eating disorders, as its availability is decreased in patients with bulimia nervosa and binge eating disorder. The promoter region contains a functional insertion/deletion polymorphism with two common alleles that have been designated the short (*S) and long (*L) alleles. The frequency of the SLC6A4*S allele has been assessed in four independent samples of patients with anorexia nervosa, but gave discrepant results. A meta-analysis was performed, which showed that the *S allele could represent a moderate but significant risk factor that increases the risk of anorexia nervosa (odds ratio [OR] = 1.38, 95% confidence interval [CI] 1.16-1.72). Eating disorders are treated using different types of psychotherapy and pharmacotherapy with antidepressants; serotonin reuptake inhibitors being the most frequently prescribed. High doses of selective serotonin reuptake inhibitors (SSRIs) are usually prescribed in eating disorders. The prevalence of non-responders (roughly one out of two), and the presence of a functional genetic polymorphism in the promotor region of SLC6A4, emphasizes the potential utility of psychopharmacogenetics in prescribing SSRIs in the treatment of patients with weight-restored anorexia nervosa. Information about genetic variations of cytochrome P450 could also facilitate pharmacotherapy by preventing the administration of high doses in poor metabolizers and identify rapid metabolizes who may require higher doses for efficacy. SLC6A4 genotyping would allow physicians to individualize selective serotonin reuptake therapy for their patients.

Influence of SERTPR and STin2 in the serotonin transporter gene on the effect of selective serotonin reuptake inhibitors in depression: a systematic review

Large differences in clinical response to selective serotonin reuptake inhibitors (SSRIs) are observed in depressive patients with different genotypes. Quantification of these differences is needed to decide if genetic testing prior to antidepressant treatment is useful. We conducted a systematic review of the literature on the influence of polymorphisms in the serotonin transporter gene (SERTPR (or 5-HTTLPR) and STin2) on SSRI response. Studies were identified by the use of MEDLINE, EmBase and PsycINFO, references of articles, reviews and information from pharmaceutical companies. Nine studies assessing the influence of SERTPR or STin2 on treatment response were included. Outcome was expressed as the percentage of decrease in depression score (HAM-D or MADRS) or as the percentage of responders (> or =50% reduction on the depression scale). Both study methodologies and study outcomes showed large heterogeneity. Weighted mean decreases in depression score for patients with the s/s, s/l and l/l genotypes were 35.4, 46.3 and 48.0% at week 4, respectively, and 53.9, 54.6 and 48.3% at week 6. Among Caucasian patients, both mean decrease in depression score and response rate were lowest in the s/s group, while among Asian patients, results were inconsistent. Weighted response rates were 36.1% for the 10/12 genotype of the STin2 polymorphism and 80.7% for the 12/12 genotype (chi2=27.8, P<0.001) (only Asians). The available evidence points to a less favourable response to SSRI treatment among Caucasian patients with the SERTPR s/s genotype and among (Asian) patients with the STin2 10/12 genotype. In view of the scarcity and heterogeneity of the studies, however, current information is insufficiently reliable as a basis for implementing genetic testing in the diagnostic work-up of the depressive patient.

A novel RNA splicing-mediated gene silencing mechanism potential for genome evolution

Over 90% of the human genome consists of non-protein-coding regions. Introns constitute most of the non-coding regions located in precursor messenger RNAs (pre-mRNAs). During pre-mRNA maturation, the introns are excised out of mRNA and thought to be completely digested prior to translation. If the introns were merely metabolic "leavings," why would the genome hold such a large amount of extraneous genetic materials? Here we show a novel posttranscriptional gene silencing system identified within mammalian introns. By packaging human spliceosome-recognition sites along with an exonic insert into an artificial intron, we observed that the splicing and processing of such an exon-containing intron in either sense or antisense conformation produced equivalent gene silencing effects, while a palindromic hairpin insert containing both sense and antisense strands resulted in synergistic effects. These findings may explain how cells respond to the presence of transgenic introns that are homologous to pre-existing exons during genomic evolution.

Serotonin transporter polymorphisms and adverse effects with fluoxetine treatment

BACKGROUND

The short (S) allele of the serotonin transporter gene-linked polymorphic region (5HTTLPR) has been associated with poorer antidepressant response in major depressive disorder (MDD) and with antidepressant-induced mania. This study investigated a possible association with treatment-emergent insomnia or agitation.

METHODS

Thirty-six outpatients with MDD were genotyped at 5HTTLPR and treated with open-label fluoxetine up to 60 mg/day. Treatment-emergent adverse effects were assessed at each study visit.

RESULTS

Of nine subjects homozygous for the "S" allele, seven (78%) developed new or worsening insomnia, versus 6 of 27 (22%) non-"S"-homozygous subjects (Fisher's exact p =.005). Similarly, six of nine subjects homozygous for the "S" allele (67%) developed agitation, versus 2 of 27 (7%) of non-"S"-homozygous subjects (Fisher's exact p =.001).

CONCLUSIONS

The "S" allele of the 5HTTLPR may identify patients at risk for developing insomnia or agitation with fluoxetine treatment. This preliminary result requires confirmation in larger samples.

Serotonin transporter promoter polymorphism in African Americans : allele frequencies and implications for treatment

BACKGROUND

Americans of African ancestry are less likely to receive a selective serotonin reuptake inhibitor (SSRI) for treatment of major depressive disorder than Americans of European ancestry. A functional insertion/deletion polymorphism in the promoter of the serotonin transporter (5-HTT) gene SLC6A4 has been shown to modulate SLC6A4 transcription, affecting response to SSRIs. Several studies in populations of predominantly European ancestry have consistently found that the SLC6A4 promoter polymorphism (referred to as the 5-HTT-linked polymorphic region; 5-HTTLPR) long (L) allele is associated with better response to SSRI treatment than the short (S) allele.

OBJECTIVE

The frequency of SLC6A4 (5-HTTLPR) alleles in 865 black Americans and Afro-Caribbeans was examined to assess possible implications for treatment.

STUDY DESIGN AND METHODS

SLC6A4 (5-HTTLPR) genotypes were determined in individuals with self-identified African ancestry from South Carolina (n = 489), western Pennsylvania (n = 207), and Tobago (n = 169). Frequencies were compared using chi-square analyses.

RESULTS

It was verified that the L allele is highly prevalent in Americans of African ancestry, ranging from 77% in western Pennsylvania to 87% in South Carolina. The frequency of the SLC6A4-(L) allele is significantly higher in African-Americans than has been reported for European-Americans (typically 56-60%). There are both statistically significant geographic differences and slight deviations from Hardy-Weinberg equilibrium.

CONCLUSIONS

Given the potential influence on treatment response, these findings have implications for the use of SSRIs in this population. The results suggest that additional studies to examine the impact of these alleles on treatment response in African-Americans are warranted.

Pharmacogenomics of psychiatric drug treatment

It is the goal of pharmacogenomics in psychiatry to establish predictive relationships between polymorphisms of candidate genes and therapeutic response to drug treatment. Polymorphisms of candidate genes related to drug mechanisms and pathophysiology of illness and defined clinical phenotype are the foundations for pharmacogenomic studies. Pharmacogenomic studies of antipsychotic response have focused on polymorphisms of genes for dopamine and serotonin receptors with most positive results reported for polymorphisms of genes of the 5HT2a and 5HT2c serotonin receptor subtypes. Although the goal of establishing individualized medicine predicated on an individual patient's genetic code has yet to be achieved, the fundamentals are now in place for second-generation investigation and more application to health care.