Heterogeneity analysis provides evidence for a genetically homogeneous subtype of bipolar-disorder

Bipolar disorder is a highly heritable brain disorder which affects an estimated 50 million people worldwide. Due to recent advances in genotyping technology and bioinformatics methodology, as well as the increase in the overall amount of available data, our understanding of the genetic underpinnings of BD has improved. A growing consensus is that BD is polygenic and heterogeneous, but the specifics of that heterogeneity are not yet well understood. Here we use a recently developed technique to investigate the genetic heterogeneity of bipolar disorder. We find strong statistical evidence for a `bicluster': a subset of bipolar subjects that exhibits a disease-specific genetic pattern. The structure illuminated by this bicluster replicates in several other data-sets and can be used to improve BD risk-prediction algorithms. We believe that this bicluster is likely to correspond to a genetically-distinct subtype of BD. More generally, we believe that our biclustering approach is a promising means of untangling the underlying heterogeneity of complex disease without the need for reliable subphenotypic data.

Exploring the genetics of lithium response in bipolar disorders

Background

Lithium (Li) remains the treatment of choice for bipolar disorders (BP). Its mood-stabilizing effects help reduce the long-term burden of mania, depression and suicide risk in patients with BP. It also has been shown to have beneficial effects on disease-associated conditions, including sleep and cardiovascular disorders. However, the individual responses to Li treatment vary within and between diagnostic subtypes of BP (e.g. BP-I and BP-II) according to the clinical presentation. Moreover, long-term Li treatment has been linked to adverse side-effects that are a cause of concern and non-adherence, including the risk of developing chronic medical conditions such as thyroid and renal disease. In recent years, studies by the Consortium on Lithium Genetics (ConLiGen) have uncovered a number of genetic factors that contribute to the variability in Li treatment response in patients with BP. Here, we leveraged the ConLiGen cohort (N=2,064) to investigate the genetic basis of Li effects in BP. For this, we studied how Li response and linked genes associate with the psychiatric symptoms and polygenic load for medical comorbidities, placing particular emphasis on identifying differences between BP-I and BP-II.

Results

We found that clinical response to Li treatment, measured with the Alda scale, was associated with a diminished burden of mania, depression, substance and alcohol abuse, psychosis and suicidal ideation in patients with BP-I and, in patients with BP-II, of depression only. Our genetic analyses showed that a stronger clinical response to Li was modestly related to lower polygenic load for diabetes and hypertension in BP-I but not BP-II. Moreover, our results suggested that a number of genes that have been previously linked to Li response variability in BP differentially relate to the psychiatric symptomatology, particularly to the numbers of manic and depressive episodes, and to the polygenic load for comorbid conditions, including diabetes, hypertension and hypothyroidism.

Conclusions

Taken together, our findings suggest that the effects of Li on symptomatology and comorbidity in BP are partially modulated by common genetic factors, with differential effects between BP-I and BP-II.

Association of polygenic score and the involvement of cholinergic and glutamatergic pathways with lithium treatment response in patients with bipolar disorder

Lithium is regarded as the first-line treatment for bipolar disorder (BD), a severe and disabling mental health disorder that affects about 1% of the population worldwide. Nevertheless, lithium is not consistently effective, with only 30% of patients showing a favorable response to treatment. To provide personalized treatment options for bipolar patients, it is essential to identify prediction biomarkers such as polygenic scores. In this study, we developed a polygenic score for lithium treatment response (Li+PGS) in patients with BD. To gain further insights into lithium's possible molecular mechanism of action, we performed a genome-wide gene-based analysis. Using polygenic score modeling, via methods incorporating Bayesian regression and continuous shrinkage priors, Li+PGS was developed in the International Consortium of Lithium Genetics cohort (ConLi+Gen: N = 2367) and replicated in the combined PsyCourse (N = 89) and BipoLife (N = 102) studies. The associations of Li+PGS and lithium treatment response - defined in a continuous ALDA scale and a categorical outcome (good response vs. poor response) were tested using regression models, each adjusted for the covariates: age, sex, and the first four genetic principal components. Statistical significance was determined at P < 0.05. Li+PGS was positively associated with lithium treatment response in the ConLi+Gen cohort, in both the categorical (P = 9.8 × 10-12, R2 = 1.9%) and continuous (P = 6.4 × 10-9, R2 = 2.6%) outcomes. Compared to bipolar patients in the 1st decile of the risk distribution, individuals in the 10th decile had 3.47-fold (95%CI: 2.22-5.47) higher odds of responding favorably to lithium. The results were replicated in the independent cohorts for the categorical treatment outcome (P = 3.9 × 10-4, R2 = 0.9%), but not for the continuous outcome (P = 0.13). Gene-based analyses revealed 36 candidate genes that are enriched in biological pathways controlled by glutamate and acetylcholine. Li+PGS may be useful in the development of pharmacogenomic testing strategies by enabling a classification of bipolar patients according to their response to treatment.

Lithium Response in Bipolar Disorder is Associated with Focal Adhesion and PI3K-Akt Networks: A Multi-omics Replication Study

Lithium is the gold standard treatment for bipolar disorder (BD). However, its mechanism of action is incompletely understood, and prediction of treatment outcomes is limited. In our previous multi-omics study of the Pharmacogenomics of Bipolar Disorder (PGBD) sample combining transcriptomic and genomic data, we found that focal adhesion, the extracellular matrix (ECM), and PI3K-Akt signaling networks were associated with response to lithium. In this study, we replicated the results of our previous study using network propagation methods in a genome-wide association study of an independent sample of 2,039 patients from the International Consortium on Lithium Genetics (ConLiGen) study. We identified functional enrichment in focal adhesion and PI3K-Akt pathways, but we did not find an association with the ECM pathway. Our results suggest that deficits in the neuronal growth cone and PI3K-Akt signaling, but not in ECM proteins, may influence response to lithium in BD.

Immunogenetics of lithium response and psychiatric phenotypes in patients with bipolar disorder

The link between bipolar disorder (BP) and immune dysfunction remains controversial. While epidemiological studies have long suggested an association, recent research has found only limited evidence of such a relationship. To clarify this, we investigated the contributions of immune-relevant genetic factors to the response to lithium (Li) treatment and the clinical presentation of BP. First, we assessed the association of a large collection of immune-related genes (4,925) with Li response, defined by the Retrospective Assessment of the Lithium Response Phenotype Scale (Alda scale), and clinical characteristics in patients with BP from the International Consortium on Lithium Genetics (ConLi+Gen, N = 2,374). Second, we calculated here previously published polygenic scores (PGSs) for immune-related traits and evaluated their associations with Li response and clinical features. We found several genes associated with Li response at p < 1×10- 4 values, including HAS3, CNTNAP5 and NFIB. Network and functional enrichment analyses uncovered an overrepresentation of pathways involved in cell adhesion and intercellular communication, which appear to converge on the well-known Li-induced inhibition of GSK-3β. We also found various genes associated with BP's age-at-onset, number of mood episodes, and presence of psychosis, substance abuse and/or suicidal ideation at the exploratory threshold. These included RTN4, XKR4, NRXN1, NRG1/3 and GRK5. Additionally, PGS analyses suggested serum FAS, ECP, TRANCE and cytokine ligands, amongst others, might represent potential circulating biomarkers of Li response and clinical presentation. Taken together, our results support the notion of a relatively weak association between immunity and clinically relevant features of BP at the genetic level.

Association of Polygenic Score and the involvement of Cholinergic and Glutamatergic Pathways with Lithium Treatment Response in Patients with Bipolar Disorder

Lithium is regarded as the first-line treatment for bipolar disorder (BD), a severe and disabling mental disorder that affects about 1% of the population worldwide. Nevertheless, lithium is not consistently effective, with only 30% of patients showing a favorable response to treatment. To provide personalized treatment options for bipolar patients, it is essential to identify prediction biomarkers such as polygenic scores. In this study, we developed a polygenic score for lithium treatment response (Li+PGS) in patients with BD. To gain further insights into lithium's possible molecular mechanism of action, we performed a genome-wide gene-based analysis. Using polygenic score modeling, via methods incorporating Bayesian regression and continuous shrinkage priors, Li+PGS was developed in the International Consortium of Lithium Genetics cohort (ConLi+Gen: N=2,367) and replicated in the combined PsyCourse (N=89) and BipoLife (N=102) studies. The associations of Li+PGS and lithium treatment response - defined in a continuous ALDA scale and a categorical outcome (good response vs. poor response) were tested using regression models, each adjusted for the covariates: age, sex, and the first four genetic principal components. Statistical significance was determined at P<����������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������.

Using polygenic scores and clinical data for bipolar disorder patient stratification and lithium response prediction: machine learning approach

BACKGROUND

Response to lithium in patients with bipolar disorder is associated with clinical and transdiagnostic genetic factors. The predictive combination of these variables might help clinicians better predict which patients will respond to lithium treatment.

AIMS

To use a combination of transdiagnostic genetic and clinical factors to predict lithium response in patients with bipolar disorder.

METHOD

This study utilised genetic and clinical data (n = 1034) collected as part of the International Consortium on Lithium Genetics (ConLi+Gen) project. Polygenic risk scores (PRS) were computed for schizophrenia and major depressive disorder, and then combined with clinical variables using a cross-validated machine-learning regression approach. Unimodal, multimodal and genetically stratified models were trained and validated using ridge, elastic net and random forest regression on 692 patients with bipolar disorder from ten study sites using leave-site-out cross-validation. All models were then tested on an independent test set of 342 patients. The best performing models were then tested in a classification framework.

RESULTS

The best performing linear model explained 5.1% (P = 0.0001) of variance in lithium response and was composed of clinical variables, PRS variables and interaction terms between them. The best performing non-linear model used only clinical variables and explained 8.1% (P = 0.0001) of variance in lithium response. A priori genomic stratification improved non-linear model performance to 13.7% (P = 0.0001) and improved the binary classification of lithium response. This model stratified patients based on their meta-polygenic loadings for major depressive disorder and schizophrenia and was then trained using clinical data.

CONCLUSIONS

Using PRS to first stratify patients genetically and then train machine-learning models with clinical predictors led to large improvements in lithium response prediction. When used with other PRS and biological markers in the future this approach may help inform which patients are most likely to respond to lithium treatment.

Sex-Dependent Shared and Nonshared Genetic Architecture Across Mood and Psychotic Disorders

BACKGROUND

Sex differences in incidence and/or presentation of schizophrenia (SCZ), major depressive disorder (MDD), and bipolar disorder (BIP) are pervasive. Previous evidence for shared genetic risk and sex differences in brain abnormalities across disorders suggest possible shared sex-dependent genetic risk.

METHODS

We conducted the largest to date genome-wide genotype-by-sex (G×S) interaction of risk for these disorders using 85,735 cases (33,403 SCZ, 19,924 BIP, and 32,408 MDD) and 109,946 controls from the PGC (Psychiatric Genomics Consortium) and iPSYCH.

RESULTS

Across disorders, genome-wide significant single nucleotide polymorphism-by-sex interaction was detected for a locus encompassing NKAIN2 (rs117780815, p = 3.2 × 10-8), which interacts with sodium/potassium-transporting ATPase (adenosine triphosphatase) enzymes, implicating neuronal excitability. Three additional loci showed evidence (p < 1 × 10-6) for cross-disorder G×S interaction (rs7302529, p = 1.6 × 10-7; rs73033497, p = 8.8 × 10-7; rs7914279, p = 6.4 × 10-7), implicating various functions. Gene-based analyses identified G×S interaction across disorders (p = 8.97 × 10-7) with transcriptional inhibitor SLTM. Most significant in SCZ was a MOCOS gene locus (rs11665282, p = 1.5 × 10-7), implicating vascular endothelial cells. Secondary analysis of the PGC-SCZ dataset detected an interaction (rs13265509, p = 1.1 × 10-7) in a locus containing IDO2, a kynurenine pathway enzyme with immunoregulatory functions implicated in SCZ, BIP, and MDD. Pathway enrichment analysis detected significant G×S interaction of genes regulating vascular endothelial growth factor receptor signaling in MDD (false discovery rate-corrected p < .05).

CONCLUSIONS

In the largest genome-wide G×S analysis of mood and psychotic disorders to date, there was substantial genetic overlap between the sexes. However, significant sex-dependent effects were enriched for genes related to neuronal development and immune and vascular functions across and within SCZ, BIP, and MDD at the variant, gene, and pathway levels.

Prediction of lithium response using genomic data

Predicting lithium response prior to treatment could both expedite therapy and avoid exposure to side effects. Since lithium responsiveness may be heritable, its predictability based on genomic data is of interest. We thus evaluate the degree to which lithium response can be predicted with a machine learning (ML) approach using genomic data. Using the largest existing genomic dataset in the lithium response literature (n = 2210 across 14 international sites; 29% responders), we evaluated the degree to which lithium response could be predicted based on 47,465 genotyped single nucleotide polymorphisms using a supervised ML approach. Under appropriate cross-validation procedures, lithium response could be predicted to above-chance levels in two constituent sites (Halifax, Cohen’s kappa 0.15, 95% confidence interval, CI [0.07, 0.24]; and Würzburg, kappa 0.2 [0.1, 0.3]). Variants with shared importance in these models showed over-representation of postsynaptic membrane related genes. Lithium response was not predictable in the pooled dataset (kappa 0.02 [− 0.01, 0.04]), although non-trivial performance was achieved within a restricted dataset including only those patients followed prospectively (kappa 0.09 [0.04, 0.14]). Genomic classification of lithium response remains a promising but difficult task. Classification performance could potentially be improved by further harmonization of data collection procedures.

Decreased core symptoms of mania and utilization of lithium/mood stabilizing anticonvulsants in U.S. bipolar I patients of African vs European ancestry

OBJECTIVE

Misdiagnosis is common in bipolar disorder and disproportionally affects racial and ethnic minorities. There is interest in better understanding the contribution of differential symptomatic illness presentation to misdiagnosis.

METHODS

Utilizing the Genetic Association Information Network (GAIN) public database, this study compared clinical phenomenology between bipolar patients of African vs European ancestry (AA = 415 vs EA = 480). The Diagnostic Interview for Genetic Studies (DIGS) was utilized to evaluate symptom endorsement contributing to diagnostic confirmation of bipolar I disorder (BPI) and lifetime medication use.

RESULTS

Elevated/euphoric mood was less endorsed in AA vs EA participants (p = 0.03). During the most severe episode of mania, AA participants, in comparison to EA participants, had a lower sum of manic symptoms (p = 0.006) and a higher rate of hallucinations (p = 0.01). During lifetime psychosis, AA participants, in comparison to EA participants, had a higher lifetime sum of delusions (p = 0.01) and hallucinations (p < 0.0001). AA participants reported lower use of lithium (p < 0.0001) and mood stabilizing anticonvulsants (p = 0.0003).

CONCLUSIONS

The differential rate of manic and psychotic symptom endorsement from a semi-structured diagnostic interview may represent differential illness presentation based on biological differences or racial or study biases (e.g. ascertainment). Increased minority recruitment in bipolar research is therefore a necessary future direction.

LIMITATIONS

Recall and interviewer bias may affect study results, but are likely diminished by the alignment of symptom endorsement and medication use.

GWAS of Suicide Attempt in Psychiatric Disorders and Association With Major Depression Polygenic Risk Scores

OBJECTIVE

More than 90% of people who attempt suicide have a psychiatric diagnosis; however, twin and family studies suggest that the genetic etiology of suicide attempt is partially distinct from that of the psychiatric disorders themselves. The authors present the largest genome-wide association study (GWAS) on suicide attempt, using cohorts of individuals with major depressive disorder, bipolar disorder, and schizophrenia from the Psychiatric Genomics Consortium.

METHODS

The samples comprised 1,622 suicide attempters and 8,786 nonattempters with major depressive disorder; 3,264 attempters and 5,500 nonattempters with bipolar disorder; and 1,683 attempters and 2,946 nonattempters with schizophrenia. A GWAS on suicide attempt was performed by comparing attempters to nonattempters with each disorder, followed by a meta-analysis across disorders. Polygenic risk scoring was used to investigate the genetic relationship between suicide attempt and the psychiatric disorders.

RESULTS

Three genome-wide significant loci for suicide attempt were found: one associated with suicide attempt in major depressive disorder, one associated with suicide attempt in bipolar disorder, and one in the meta-analysis of suicide attempt in mood disorders. These associations were not replicated in independent mood disorder cohorts from the UK Biobank and iPSYCH. No significant associations were found in the meta-analysis of all three disorders. Polygenic risk scores for major depression were significantly associated with suicide attempt in major depressive disorder (R²=0.25%), bipolar disorder (R²=0.24%), and schizophrenia (R²=0.40%).

CONCLUSIONS

This study provides new information on genetic associations and demonstrates that genetic liability for major depression increases risk for suicide attempt across psychiatric disorders. Further collaborative efforts to increase sample size may help to robustly identify genetic associations and provide biological insights into the etiology of suicide attempt.

Genome-wide association study identifies 30 loci associated with bipolar disorder

Bipolar disorder is a highly heritable psychiatric disorder. We performed a genome-wide association study (GWAS) including 20,352 cases and 31,358 controls of European descent, with follow-up analysis of 822 variants with P < 1 × 10-4 in an additional 9,412 cases and 137,760 controls. Eight of the 19 variants that were genome-wide significant (P < 5 × 10-8) in the discovery GWAS were not genome-wide significant in the combined analysis, consistent with small effect sizes and limited power but also with genetic heterogeneity. In the combined analysis, 30 loci were genome-wide significant, including 20 newly identified loci. The significant loci contain genes encoding ion channels, neurotransmitter transporters and synaptic components. Pathway analysis revealed nine significantly enriched gene sets, including regulation of insulin secretion and endocannabinoid signaling. Bipolar I disorder is strongly genetically correlated with schizophrenia, driven by psychosis, whereas bipolar II disorder is more strongly correlated with major depressive disorder. These findings address key clinical questions and provide potential biological mechanisms for bipolar disorder.

Investigating polygenic burden in age at disease onset in bipolar disorder: Findings from an international multicentric study

OBJECTIVES

Bipolar disorder (BD) with early disease onset is associated with an unfavorable clinical outcome and constitutes a clinically and biologically homogenous subgroup within the heterogeneous BD spectrum. Previous studies have found an accumulation of early age at onset (AAO) in BD families and have therefore hypothesized that there is a larger genetic contribution to the early-onset cases than to late onset BD. To investigate the genetic background of this subphenotype, we evaluated whether an increased polygenic burden of BD- and schizophrenia (SCZ)-associated risk variants is associated with an earlier AAO in BD patients.

METHODS

A total of 1995 BD type 1 patients from the Consortium of Lithium Genetics (ConLiGen), PsyCourse and Bonn-Mannheim samples were genotyped and their BD and SCZ polygenic risk scores (PRSs) were calculated using the summary statistics of the Psychiatric Genomics Consortium as a training data set. AAO was either separated into onset groups of clinical interest (childhood and adolescence [≤18 years] vs adulthood [>18 years]) or considered as a continuous measure. The associations between BD- and SCZ-PRSs and AAO were evaluated with regression models.

RESULTS

BD- and SCZ-PRSs were not significantly associated with age at disease onset. Results remained the same when analyses were stratified by site of recruitment.

CONCLUSIONS

The current study is the largest conducted so far to investigate the association between the cumulative BD and SCZ polygenic risk and AAO in BD patients. The reported negative results suggest that such a polygenic influence, if there is any, is not large, and highlight the importance of conducting further, larger scale studies to obtain more information on the genetic architecture of this clinically relevant phenotype.

Detecting significant genotype-phenotype association rules in bipolar disorder: market research meets complex genetics

Background

Disentangling the etiology of common, complex diseases is a major challenge in genetic research. For bipolar disorder (BD), several genome-wide association studies (GWAS) have been performed. Similar to other complex disorders, major breakthroughs in explaining the high heritability of BD through GWAS have remained elusive. To overcome this dilemma, genetic research into BD, has embraced a variety of strategies such as the formation of large consortia to increase sample size and sequencing approaches. Here we advocate a complementary approach making use of already existing GWAS data: a novel data mining procedure to identify yet undetected genotype–phenotype relationships. We adapted association rule mining, a data mining technique traditionally used in retail market research, to identify frequent and characteristic genotype patterns showing strong associations to phenotype clusters. We applied this strategy to three independent GWAS datasets from 2835 phenotypically characterized patients with BD. In a discovery step, 20,882 candidate association rules were extracted.

Results

Two of these rules—one associated with eating disorder and the other with anxiety—remained significant in an independent dataset after robust correction for multiple testing. Both showed considerable effect sizes (odds ratio ~ 3.4 and 3.0, respectively) and support previously reported molecular biological findings.

Conclusion

Our approach detected novel specific genotype–phenotype relationships in BD that were missed by standard analyses like GWAS. While we developed and applied our method within the context of BD gene discovery, it may facilitate identifying highly specific genotype–phenotype relationships in subsets of genome-wide data sets of other complex phenotype with similar epidemiological properties and challenges to gene discovery efforts.

Electronic supplementary material

The online version of this article (10.1186/s40345-018-0132-x) contains supplementary material, which is available to authorized users.

Pharmacogenetic profile and major depressive and/or bipolar disorder treatment: a retrospective, cross-sectional study

Aim: To compare pharmacogenetic test predictions with self-reported treatment experience and side effect tolerability among patients with depression taking psychotherapeutic medications. Methods: Subjects completed a survey recalling medication effectiveness and side effects and then underwent pharmacogenetic testing. Results: Our 15 gene pharmacogenetic panel predicted efficacy (p < 0.001) but did not predict side effect tolerability (p = 0.70) in a group of 352 patients. The pharmacogenetic panel and reported efficacy corresponded 60% of the time and medication tolerability agreed 71% of the time. Conclusion: Pharmacogenetic testing may be a useful adjunct to predict efficacy of medications used to treat depression.

A loop-counting method for covariate-corrected low-rank biclustering of gene-expression and genome-wide association study data

A common goal in data-analysis is to sift through a large data-matrix and detect any significant submatrices (i.e., biclusters) that have a low numerical rank. We present a simple algorithm for tackling this biclustering problem. Our algorithm accumulates information about 2-by-2 submatrices (i.e., 'loops') within the data-matrix, and focuses on rows and columns of the data-matrix that participate in an abundance of low-rank loops. We demonstrate, through analysis and numerical-experiments, that this loop-counting method performs well in a variety of scenarios, outperforming simple spectral methods in many situations of interest. Another important feature of our method is that it can easily be modified to account for aspects of experimental design which commonly arise in practice. For example, our algorithm can be modified to correct for controls, categorical- and continuous-covariates, as well as sparsity within the data. We demonstrate these practical features with two examples; the first drawn from gene-expression analysis and the second drawn from a much larger genome-wide-association-study (GWAS).

Association of Polygenic Score for Schizophrenia and HLA Antigen and Inflammation Genes With Response to Lithium in Bipolar Affective Disorder: A Genome-Wide Association Study

IMPORTANCE

Lithium is a first-line mood stabilizer for the treatment of bipolar affective disorder (BPAD). However, the efficacy of lithium varies widely, with a nonresponse rate of up to 30%. Biological response markers are lacking. Genetic factors are thought to mediate treatment response to lithium, and there is a previously reported genetic overlap between BPAD and schizophrenia (SCZ).

OBJECTIVES

To test whether a polygenic score for SCZ is associated with treatment response to lithium in BPAD and to explore the potential molecular underpinnings of this association.

DESIGN, SETTING, AND PARTICIPANTS

A total of 2586 patients with BPAD who had undergone lithium treatment were genotyped and assessed for long-term response to treatment between 2008 and 2013. Weighted SCZ polygenic scores were computed at different P value thresholds using summary statistics from an international multicenter genome-wide association study (GWAS) of 36 989 individuals with SCZ and genotype data from patients with BPAD from the Consortium on Lithium Genetics. For functional exploration, a cross-trait meta-GWAS and pathway analysis was performed, combining GWAS summary statistics on SCZ and response to treatment with lithium. Data analysis was performed from September 2016 to February 2017.

MAIN OUTCOMES AND MEASURES

Treatment response to lithium was defined on both the categorical and continuous scales using the Retrospective Criteria of Long-Term Treatment Response in Research Subjects with Bipolar Disorder score. The effect measures include odds ratios and the proportion of variance explained.

RESULTS

Of the 2586 patients in the study (mean [SD] age, 47.2 [13.9] years), 1478 were women and 1108 were men. The polygenic score for SCZ was inversely associated with lithium treatment response in the categorical outcome, at a threshold P < 5 × 10-2. Patients with BPAD who had a low polygenic load for SCZ responded better to lithium, with odds ratios for lithium response ranging from 3.46 (95% CI, 1.42-8.41) at the first decile to 2.03 (95% CI, 0.86-4.81) at the ninth decile, compared with the patients in the 10th decile of SCZ risk. In the cross-trait meta-GWAS, 15 genetic loci that may have overlapping effects on lithium treatment response and susceptibility to SCZ were identified. Functional pathway and network analysis of these loci point to the HLA antigen complex and inflammatory cytokines.

CONCLUSIONS AND RELEVANCE

This study provides evidence for a negative association between high genetic loading for SCZ and poor response to lithium in patients with BPAD. These results suggest the potential for translational research aimed at personalized prescribing of lithium.

Exome sequencing in the knockin mice generated using the CRISPR/Cas system

Knockin (KI) mouse carrying a point mutation has been an invaluable tool for disease modeling and analysis. Genome editing technologies using the CRISPR/Cas system has emerged as an alternative way to create KI mice. However, if the mice carry nucleotide insertions and/or deletions (InDels) in other genes, which could have unintentionally occurred during the establishment of the KI mouse line and potentially have larger impact than a point mutation, it would confound phenotyping of the KI mice. In this study, we performed whole exome sequencing of multiple lines of F1 heterozygous Ntrk1 KI mice generated using the CRISPR/Cas system in comparison to that of a wild-type mouse used as a control. We found three InDels in four KI mice but not in a control mouse. In vitro digestion assay suggested that each InDel occurred as a de novo mutation, was carried-over from the parental mice, or was incorporated through the Cas9 nuclease mediated off-target cleavage. These results suggest that frequency of InDels found in KI mice generated by the CRISPR/Cas technology is not high, but cannot be neglected and careful assessment of these mutations is warranted.

The pharmacodynamic properties of lurasidone and their role in its antidepressant efficacy in bipolar disorder

The treatment of bipolar depression is one of the most challenging issues in contemporary psychiatry. Currently only quetiapine, the olanzapine-fluoxetine combination and recently lurasidone are officially FDA-approved against this condition. The neurobiology of bipolar depression and the possible targets of bipolar antidepressant therapy remain elusive. The current study investigated whether the pharmacodynamic properties of lurasidone fit to a previously developed model which was the first to be derived on the basis of the strict combination of clinical and preclinical data with no input from theory or opinion. The authors performed a complete and systematic review of the literature to identify the pharmacodynamic properties of lurasidone. The original model suggests that a constellation of effects on different receptors are necessary but the serotonin reuptake inhibition does not seem to play a significant role for bipolar depression. On the contrary norepinephrine activity seems to be very important. Probably the early antidepressant effect can be achieved through an agonistic activity at 5HT-1A and antagonism at alpha1 noradrenergic and 5-HT2A receptors, but the presence of a norepinephrine reuptake inhibition is essential in order to sustain it. Overall the properties of lurasidone fit well the model and add to its validity. A point that needs clarification is norepinephrine reuptake inhibition which is not yet studied for lurasidone.

Mitochondrial mutations and polymorphisms in psychiatric disorders

Mitochondrial deficiencies with unknown causes have been observed in schizophrenia (SZ) and bipolar disorder (BD) in imaging and postmortem studies. Polymorphisms and somatic mutations in mitochondrial DNA (mtDNA) were investigated as potential causes with next generation sequencing of mtDNA (mtDNA-Seq) and genotyping arrays in subjects with SZ, BD, major depressive disorder (MDD), and controls. The common deletion of 4,977 bp in mtDNA was compared between SZ and controls in 11 different vulnerable brain regions and in blood samples, and in dorsolateral prefrontal cortex (DLPFC) of BD, SZ, and controls. In a separate analysis, association of mitochondria SNPs (mtSNPs) with SZ and BD in European ancestry individuals (n = 6,040) was tested using Genetic Association Information Network (GAIN) and Wellcome Trust Case Control Consortium 2 (WTCCC2) datasets. The common deletion levels were highly variable across brain regions, with a 40-fold increase in some regions (nucleus accumbens, caudate nucleus and amygdala), increased with age, and showed little change in blood samples from the same subjects. The common deletion levels were increased in the DLPFC for BD compared to controls, but not in SZ. Full mtDNA genome resequencing of 23 subjects, showed seven novel homoplasmic mutations, five were novel synonymous coding mutations. By logistic regression analysis there were no significant mtSNPs associated with BD or SZ after genome wide correction. However, nominal association of mtSNPs (p < 0.05) to SZ and BD were found in the hypervariable region of mtDNA to T195C and T16519C. The results confirm prior reports that certain brain regions accumulate somatic mutations at higher levels than blood. The study in mtDNA of common polymorphisms, somatic mutations, and rare mutations in larger populations may lead to a better understanding of the pathophysiology of psychiatric disorders.

Genomewide association studies: history, rationale, and prospects for psychiatric disorders

OBJECTIVE

The authors conducted a review of the history and empirical basis of genomewide association studies (GWAS), the rationale for GWAS of psychiatric disorders, results to date, limitations, and plans for GWAS meta-analyses.

METHOD

A literature review was carried out, power and other issues discussed, and planned studies assessed.

RESULTS

Most of the genomic DNA sequence differences between any two people are common (frequency >5%) single nucleotide polymorphisms (SNPs). Because of localized patterns of correlation (linkage disequilibrium), 500,000 to 1,000,000 of these SNPs can test the hypothesis that one or more common variants explain part of the genetic risk for a disease. GWAS technologies can also detect some of the copy number variants (deletions and duplications) in the genome. Systematic study of rare variants will require large-scale resequencing analyses. GWAS methods have detected a remarkable number of robust genetic associations for dozens of common diseases and traits, leading to new pathophysiological hypotheses, although only small proportions of genetic variance have been explained thus far and therapeutic applications will require substantial further effort. Study design issues, power, and limitations are discussed. For psychiatric disorders, there are initial significant findings for common SNPs and for rare copy number variants, and many other studies are in progress.

CONCLUSIONS

GWAS of large samples have detected associations of common SNPs and of rare copy number variants with psychiatric disorders. More findings are likely, since larger GWAS samples detect larger numbers of common susceptibility variants, with smaller effects. The Psychiatric GWAS Consortium is conducting GWAS meta-analyses for schizophrenia, bipolar disorder, major depressive disorder, autism, and attention deficit hyperactivity disorder. Based on results for other diseases, larger samples will be required. The contribution of GWAS will depend on the true genetic architecture of each disorder.

Association analysis of GRK3 gene promoter variants in cocaine abuse

The G protein-coupled receptor kinase 3 gene (GRK3) is a candidate gene for cocaine addiction because it is involved in the regulation of several neurotransmitter receptors, including the response to dopaminergic agonists such as methamphetamine and cocaine. We hypothesized that genetic variants in the GRK3 gene might be associated with an increased risk of cocaine addiction. To test this, we genotyped three variants located in 5' untranslated and promoter regions of the gene in a sample of 711 cocaine users and 862 healthy control individuals from Sao Paulo, Brazil. Genotypic, allelic and haplotypic analyses provided no evidence for an association between alleles at these polymorphisms and cocaine abuse in this sample. Population stratification was tested for and its effect corrected for, but this did not affect the association test results. In conclusion, our results do not support a major role for GRK3 gene promoter variants in cocaine addiction.

A dopamine transporter gene functional variant associated with cocaine abuse in a Brazilian sample

The dopamine (DA) transporter DAT1 is a major target bound by cocaine in brain. We examined the influence of functional genetic variants in DAT1 on cocaine addiction. Repeat polymorphisms, including a 30-bp variable-number tandem repeat (VNTR) in intron 8 (Int8 VNTR) with two common alleles, were genotyped in cocaine-dependent abusers (n = 699) and in controls with no past history of drug abuse (n = 866) from São Paulo, Brazil. Positive association was observed with allele 3 of the Int8 VNTR and cocaine abuse (allele odds ratio = 1.2, 95% confidence interval = 1.01-1.37, P = 0.036; 3/3 homozygote odds ratio = 1.45, 95% confidence interval = 1.18-1.78, P = 0.0008). Population stratification was assessed and did not affect the results. Haplotypic analyses using additional polymorphisms indicated that the Int8 VNTR is responsible for the observed association. Functional analyses in reporter-gene constructs, demonstrated that allele 3 mediates significant (P < 0.05) but small reduced expression compared with the "protective" allele 2. This difference increased when 1 and 10 muM cocaine was added to the cell culture ( approximately 40% reduction of the 3 allele expression versus the 2 allele). The 3 allele also demonstrated approximately 3-fold-increased expression over the 2 allele in response to KCl plus forskolin challenge. We demonstrate a robust association between cocaine dependence and a VNTR allele in SLC6A3, conferring a small but detectable effect, and we show that this VNTR may be functional. This study suggests that DAT1 gene variation may play a role in cocaine dependence etiology.

Affective state and EEG sleep profile in response to rapid tryptophan depletion in recently recovered nonmedicated depressed individuals

BACKGROUND

The current study examines whether a tryptophan-free amino acid drink (TFD) causes a transient mood relapse in unmedicated patients recently recovered from major depression. TFD is thought to reduce cerebral serotonin, a neurotransmitter implicated in depression. Some studies report that TFD reverses the antidepressant and REM-suppression effects of selective serotonin reuptake inhibitors (SSRIs).

METHODS

Following an average of 10 weeks of Cognitive Behavioral Therapy (CBT), 13 recovered patients who achieved 50% or greater reduction on the initial Hamilton Rating Scale of Depression (HRSD) underwent a double-blind challenge with the TFD and a control drink. In order to demonstrate the central physiological effects of the TFD on REM sleep in these patients, all night polygraphic sleep recordings were obtained before and after the TFD and control drink.

RESULTS

Relative to the control drink, TFD decreased REM latency and plasma concentrations of tryptophan but had no statistically significant effect on mood symptoms as measured by the HRSD, Beck Depression Inventory (BDI), and Profile of Mood States (POMS).

LIMITATIONS

High participant attrition, a physiologically active control drink, physical side effects in response to both drinks, and low statistical power may be methodological considerations that limit interpretation of findings.

CONCLUSIONS

The failure to find a transient mood relapse after the TFD may suggest that: (a) nonpharmacological recovery from depression does not occur via serotonergic mechanisms, (b) participant variables may be operating, or (c) CBT alters psychological responses to unfavorable biological states.

A quantitative neuromotor predictor of antidepressant non-response in patients with major depression

Predicting response to antidepressant medication has been a challenge to clinicians and researchers for decades. Attention has been paid to the role of motor retardation as a putative indicator of treatment response, yet previous findings have been mixed. One reason for this inconsistency may be related to the subjective nature of motor retardation and how it is assessed. In the present study, we adopted a measure of motor programming previously shown to characterize parkinsonian bradykinesia to test whether neuromotor function could predict response to antidepressant treatment. Twenty-eight patients (14 males and 14 females with a mean age of 42.0 years) meeting DSM-IV criteria for a depressive disorder were randomized to receive 8 weeks of treatment with one of three antidepressant medications (sertraline, phenelzine, or bupropion). Treatment outcomes were assessed using the 17-item version of the Hamilton Rating Scale for Depression (HRSD). Patients were considered asymptomatic if their post-treatment HRSD total score was equal to or less than 7. Treatment responders (n=15) had significantly less baseline impairment (P=0.01) on the neuromotor measure than non-responders (n=13). There was a significant relationship between amount of improvement on the HRSD and severity of baseline neuromotor function (r=-0.51; P=0.006). No significant group effects were found for baseline psychomotor slowing or clinical ratings of motor retardation. These results demonstrate that a quantitative measure of motor programming may be a useful predictor of antidepressant non-response.

Linkage disequilibrium mapping at DAT1, DRD5 and DBH narrows the search for ADHD susceptibility alleles at these loci

Abnormalities in dopaminergic neurotransmission are now accepted as factors in predisposing to ADHD. Evidence of associations between dopamine transporter gene polymorphism and ADHD was first reported by Cook et al. We confirmed the DAT1 association and also identified two additional susceptibility loci at the DRD5 and DBH. Notably, none of the associated variants at these three genes are known to be expressed. Other variants within or closely mapped to the associated alleles are likely to be relevant. In this investigation, we analyse additional markers creating a high-density map across and flanking these genes, and measure intermarker linkage disequilibrium (LD). None of the newly examined markers were more strongly associated with ADHD. At DAT1, the pattern of intermarker LD and haplotype association with the phenotype between exon 9 and the 3' of the gene suggests that the functional variant at DAT1 may be located to this region. For DRD5, three markers, covering a region of approximately 68 kb including the single DRD5 exon are all associated with disease, and thus do not provide localizing information. However, the data for DBH point to a region close to the centre of the gene. Correlation between D' and physical distance was observed between markers at DAT1 and DRD5 for distances less than 50 kb. This was not the case for DBH, where LD breakdown was observed between the intron 5 and intron 9 polymorphisms although they are only 9 kb apart. Further genetic analysis is unlikely to refine the location of susceptibility variants and functional assessment of variants within associated regions is required.

Effects of rapid tryptophan depletion on sleep electroencephalogram and mood in subjects with partially remitted depression on bupropion

Serotonin has been implicated in both sleep and mood regulation. When central serotonin was depleted with a tryptophan-free amino acid drink (TFD), some studies have reported that the antidepressant benefits were reversed in partially remitted patients treated with SSRIs. Other studies showed that the TFD increased rapid eye movement (REM) sleep in both normal males and in remitted depression patients on selective serotonin reuptake inhibitors (SSRIs) without affecting mood. In this study, we administered a TFD to patients with remitted depression who were being treated with bupropion, an antidepressant whose mechanism of action apparently does not affect the serotonin system. We hypothesized that the TFD would increase the propensity for REM sleep without affecting depression ratings. Eight partially remitted depression subjects on bupropion were administered a TFD and a control drink containing tryptophan in double-blind, random order on separate days. The effects of these drinks were monitored with sleep electroencephalograms, mood ratings, and plasma tryptophan measures comparing baseline, TFD, and control nights. The TFDs reduced REM latency and stage 2 percent and increased REM time and percent. Subjective measures of elation, vigor, and friendliness significantly decreased on both TFD and control drinks but depression ratings did not. Plasma levels of tryptophan decreased with the TFD. Although the TFD altered REM sleep, certain mood measures, and plasma tryptophan levels, no relapses into depression were seen with our subjects. Bupropion alone did not affect sleep measures.

Genetics of affective disorders

Despite substantial evidence for heritability in affective disorders the contributing genes have proven elusive. Here we discuss the genetic epidemiology of depression, as well as methodological issues and results from molecular genetic studies. There has been rapid advances in genetics, genomics and statistical modelling, facilitating the search for molecular mechanisms underlying affective disorders and several strategies reviewed in this paper hold promise to provide progress in the field. Considering the poorly understood biological basis of vulnerability to affective disorders, the identification of genes involved in the pathophysiology will unravel mechanisms and pathways that could permit more personalized therapeutic strategies and result in new targets for pharmacological intervention.

Rapid tryptophan depletion plus a serotonin 1A agonist: competing effects on sleep in healthy men

In the present study, we hypothesized that the REM-suppressing effects of 5-HT(1A) receptor stimulation would counteract the REM-disinhibiting effects of rapid tryptophan depletion (RTD), and vice versa. We administered RTD plus ipsapirone (10 mg, p.o.) or RTD plus placebo to 10 healthy men. In contrast to our previous findings but partially consistent with other studies, RTD in combination with placebo did not produce a significant enhancement of any REM sleep measure. The combination of RTD and ipsapirone produced a significant suppression of REM sleep that was remarkably similar to the effect of ipsapirone alone. These data appear to deepen the mystery of variable and inconsistent RTD-induced responses in healthy subjects. In the case of REM sleep measures, this differs markedly from the consistent RTD-induced REM-disinhibiting effect seen in medicated depressed patients.

An open-label, 12-week clinical and sleep EEG study of nefazodone in chronic combat-related posttraumatic stress disorder

BACKGROUND

We examined the effects of nefazodone on polysomnographic sleep measures and subjective reports of sleep quality and nightmares. as well as other symptoms, in patients with chronic combat-related posttraumatic stress disorder (PTSD) during a 12-week, open-label clinical trial. To our knowledge, this is the first polysomnographic study of treatment in patients with PTSD.

METHOD

The subjects were 12 male veterans (mean age = 54 years) who met DSM-IV diagnostic criteria for PTSD (mean duration = 30 years). All but I patient also met DSM-IV criteria for major depressive disorder. Patients were evaluated weekly with clinical ratings in an open-label clinical trial. Polysomnographic recordings for 2 consecutive nights were obtained before treatment and at 2, 4, 8, and 12 weeks. The dose of nefazodone was adjusted according to individual clinical needs. Final mean daily dose was 441 mg.

RESULTS

The patients reported significantly fewer nightmares and sleep problems during treatment. Nevertheless, contrary to studies in depressed patients, nefazodone did not significantly affect polysomnographic sleep measures compared with baseline. In addition, the patients showed significant improvement in the Clinical Global Impressions of PTSD symptoms (global score, hyperarousals and intrusions subscales), the Clinician-Administered PTSD Scale (global, hyperarousal, and intrusions subscales), the Hamilton Rating Scale for Depression (HAM-D). and the Beck Depression Inventory (BDI).

CONCLUSION

These patients with chronic, treatment-resistant, combat-related PTSD showed significant improvement of subjective symptoms of nightmares and sleep disturbance, as well as depression and PTSD symptoms. in this 12-week open-label clinical trial. Nevertheless, objective polysomnographic sleep measures did not change. Further studies, including double-blind. placebo-controlled trials, are needed to extend these findings and to understand the relationships between the physiology of sleep and symptoms of poor sleep and nightmares.

A pedigree of one family with delayed sleep phase syndrome

The prevalence of delayed sleep phase syndrome (DSPS) has been estimated to be quite low. Although no genetic inheritance pattern has been described, it has been reported that close to 50% of DSPS patients have biological relatives with similar symptoms. A pedigree of one extended family with symptoms suggestive of DSPS has been identified. Morningness-eveningness questionnaires were administered to all first- and second-degree relatives of a proband identified with DSPS. A total of 51 (86%) questionnaires were returned, and 6 adult biological relatives of 27 (22%) showed a preference for eveningness, which is much higher than reported in the general population. Both the paternal and maternal branches contained affected individuals, suggesting the possibility of a bilineal mode of inheritance. While the trait did not obey simple Mendelian inheritance, the vertical patterns of transmission were consistent with either an autosomal dominant mode of inheritance with incomplete penetrance or a multifactorial mode of inheritance. These data provide some preliminary support to the notion that eveningness, and thus DSPS, may have a genetic component. The prevalence of symptoms suggestive of DSPS is higher in this family than reported in the general population. Case reports such as this support the utility of larger, more systematic studies. It is unclear whether this degree of familiarity is representative of that in the general population.

Relationship of mood disturbance to cigarette smoking status among 252 patients with a current mood disorder

BACKGROUND

The relationship between cigarette smoking and mood has received increasing attention. This retrospective study evaluated the relationship between mood disturbance and cigarette smoking status among patients with a current mood disorder. The association between level of nicotine dependence and severity of mood disturbance was also evaluated among current smokers.

METHOD

Retrospective data for 252 patients (63.5% male, 85.0% white) admitted for treatment of a mood disorder at the San Diego Veteran Affairs Mental Health Clinical Research Center between November 1988 and June 1997 were studied. All current cigarette smokers at admission (N = 126) were matched with nonsmokers (N = 126) on the primary DSM-IV Axis I mood disorder diagnosis, admission status (inpatient or outpatient), gender, age (+/- 5 years), and ethnicity. The Hamilton Rating Scale for Depression (HAM-D), the Beck Depression Inventory, and the Profile of Mood States (POMS) were administered to patients on admission. Conditional logistic regression analysis for matched sets with a backward elimination was used to identify factors independently predictive of current smoking status.

RESULTS

A greater number of cups of coffee consumed per day (p = .002), a history of alcoholism (p = .004), and higher POMS fatigue subscale scores (p = .007) were predictive of current smoking status. Among current smokers, the HAM-D terminal insomnia item was positively associated with mean number of cigarettes smoked per day (p = .012).

CONCLUSION

Cigarette smoking should be addressed in the treatment of patients with a current mood disorder. Smokers experience greater levels of fatigue than nonsmokers. In addition, higher cigarette consumption levels are associated with mild-to-severe symptoms of terminal insomnia.

The effects of transdermal nicotine therapy for smoking cessation on depressive symptoms in patients with major depression

This study examines the effects of transdermal nicotine patches for smoking cessation on depressive and withdrawal symptoms among 38 non-medicated subjects with Major Depressive Disorder. The study was conducted over a 29-day period, which included a 7 day baseline phase, a 14 day treatment phase, and an 8 day placebo phase. During the treatment phase subjects received either active nicotine patches (N = 18) or placebo patches (N = 20) that were administered in a randomized, double-blind fashion. The target quit date (TQD) was day 8. Significantly, more subjects in the placebo group than in the nicotine group resumed smoking following the TQD (50% vs. 22%). There was little evidence for effects of active nicotine patches on measures of mood (HRSD, BDI, POMS) or withdrawal symptoms among subjects that remained abstinent throughout the study (N = 24). Those who resumed smoking had more severe withdrawal symptoms than those who remained abstinent. One patient in the placebo group (n = 20) became more depressed after 2 weeks of abstinence. None of the patients in the nicotine group (n = 18) became more depressed.

Clinical and physiological consequences of rapid tryptophan depletion

We review here the rapid tryptophan depletion (RTD) methodology and its controversial association with depressive relapse. RTD has been used over the past decade to deplete serotonin (5-hydroxy-tryptamine, or 5-HT) in humans and to probe the role of the central serotonin system in a variety of psychiatric conditions. Its current popularity was stimulated by reports that RTD reversed the antidepressant effects of selective serotonin reuptake inhibitors (SSRIs) and monoamine oxidase inhibitors (MAOIs) in remitted patients with a history of depression but not in patients treated with antidepressants which promote catecholaminergic rather than serotonergic neurotransmission (such as tricyclic antidepressants or buproprion). However, RTD has inconsistent effects in terms of full clinical relapse in depressed patients. Pooling the data from all published reports, patients who are either unmedicated and/or fully remitted are much less likely to experience relapse (7 of 61, or approximately 9%) than patients who are recently medicated and partially remitted (63 of 133, or approximately 47%; although, the numbers here may reflect patient overlap between reports). Recently remitted patients who have been treated with non-pharmacological therapies such as total sleep deprivation, electroconvulsive therapy, or bright light therapy also do not commonly show full clinical relapse with RTD. We briefly review RTD effects in other psychiatric disorders, many of which are treated with SSRIs. There is accumulating evidence to suggest that RTD affects central serotonergic neurotransmission. Nevertheless, many questions remain about the ability of RTD to reverse the beneficial effects of SSRIs or MAOIs, or to induce symptoms in unmedicated symptomatic or asymptomatic patients.

Rapid tryptophan depletion, sleep electroencephalogram, and mood in men with remitted depression on serotonin reuptake inhibitors

BACKGROUND

In previous studies, depletion of brain serotonin by administration of a tryptophan-free amino acid drink (TFD) (1) temporarily reversed the antidepressant effects of selective serotonin reuptake inhibitors (SSRIs) in euthymic patients who had a history of major depression, and (2) enhanced rapid eye movement (REM) sleep in normal volunteers. In this study, we hypothesized that the TFD would not only increase depressive symptoms but also the propensity for REM sleep in euthymic patients treated with SSRIs.

METHODS

Ten fully remitted, medicated male patients who had a history of major depressive episode ingested a 100-g TFD (the experimental dose) or a 25-g TFD (designed to be the control drink) in double-blind, random order on separate days. The effects were assessed with mood ratings, plasma tryptophan concentrations, and an all-night sleep electroencephalogram.

RESULTS

The TFDs produced a dose-dependent reduction in plasma tryptophan concentrations, sleep latency, and REM latency, as well as increased REM percentage, REM minutes, REM density, and total sleep time. Neither strength of TFD altered mood to a clinically significant degree.

CONCLUSIONS

Although the TFD affected plasma tryptophan concentrations and various sleep measures, our study did not confirm previous reports that TFD temporarily reversed the antidepressant effects of SSRIs in euthymic patients. Our patients, however, had been treated for a longer period with SSRIs and were more fully remitted at the time of the study. Our results suggest that TFD-induced relapse in SSRI-treated patients in remission decreases as a function of treatment duration, degree of remission, or both.

Effects of a tryptophan-free amino acid drink challenge on normal human sleep electroencephalogram and mood

BACKGROUND

Serotonin has been implicated in the regulation of sleep and mood. In animals a tryptophan-free amino acid drink (TFD) challenge has been found to reduce brain serotonin. We hypothesized this TFD would produce alterations in electroencephalographic (EEG) sleep commonly associated with depression, i.e. an enhancement of rapid eye movement (REM) sleep, and adversely affect mood ratings in humans.

METHODS

We investigated the effects of a TFD challenge in 11 healthy male subjects on EEG sleep and mood (assessed by Profile of Mood States). All subjects received on separate occasions an experimental drink containing approximately 100 g of an amino acid mixture (100% TFD) and a control drink containing one fourth strength (25% TFD) of the experimental drink 5 hours prior to sleep (6:00 PM).

RESULTS

Both drinks significantly decreased plasma tryptophan levels 5 hours postchallenge (11:00 PM). Both drinks significantly decreased REM latency, and the 25% TFD also increased REM time and REM% compared to baseline. No significant changes were found in subjective ratings of depression; however, subjects reported confusion and tension and a decrease in elation, vigor, and friendliness compared with baseline.

CONCLUSIONS

These TFD findings further support the involvement of serotonin deficiency in EEG sleep findings commonly seen in depression.

Lack of association of catechol-O-methyltransferase (COMT) functional polymorphism in bipolar affective disorder

Abnormal catecholamine transmission has been implicated in the pathogenesis of mood disorders. Consequently, alterations in genes that are involved in catecholamine metabolism could be potential candidates for bipolar affective disorder (BPD) vulnerability. One such candidate is catechol-O-methyltransferase (COMT). A functional polymorphism has recently been characterized that is responsible for substantial variability in COMT enzymatic activity. A relatively low activity allele is associated with a methionine residue at amino acid 158 of membrane bound COMT whereas a high activity variant has a valine at this site. We have now screened 63 unrelated patients with BPD for this functional polymorphism. However, no significant association was detected. This suggests that the codon 158 COMT polymorphism is not a susceptibility gene in BPD.

Ipsapirone, a 5-HT1A agonist, suppresses REM sleep equally in unmedicated depressed patients and normal controls

To determine whether ipsapirone, a 5-HT1A agonist, differentially suppresses REM sleep in depressed patients compared with normal controls, we administered placebo, ipsapirone 10 mg, or ipsapirone 20 mg in a double-blind, random order before bedtime in 18 unmedicated patients with depression and 16 age-matched, gender-matched normal controls. Compared to placebo, ipsapirone affected REM sleep measures equally in depressed patients and controls as follows: (1) increased REM latency; (2) reduced total REM percent, REM time, and REM density; and (3) delayed the onset of REM sleep. In addition, ipsapirone had similar effects in patients and controls in other sleep measures: (1) reduced total sleep time; (2) delayed sleep onset time; and (3) increased sleep latency, stage 1%, stage 2%, the amount of stage 3 & 4 sleep in the first non-REM period, and wake time after sleep onset. The study does not support the hypothesis that downregulated 5-HT1A receptors mediate the pathophysiology or sleep disturbances of depression, although further studies are needed as these patients did not differ from controls in baseline sleep measures.

Comparison of descriptive variables for symptomatic volunteers and clinical patients with anxiety disorders

Worry about the generalizability of findings derived from clinical trials is a nagging problem. Because most clinical trials use individuals recruited by advertisements rather than patients solicited from clinical practice, bias in subject recruitment is a major concern. This paper compares and contrasts the demographic characteristics, symptomatologies, functional disabilities, health beliefs, and health expectations of clinical outpatients to those of subjects recruited from the media (symptomatic volunteers) for pharmacologic trials. Clinical patients were slightly younger, better educated, wealthier, and were more likely to be married. They had more recent exposure to benzodiazepines and antidepressants and were more likely to view their current condition as amenable to psychotherapy. They were more likely to feel that their symptoms would get worse without some type of treatment and to believe that treatment would cure them. The symptomatic volunteers had more presenting symptoms than the clinical patients. The two groups had similar Sheehan Disability Scale scores. These results suggest that further study is warranted of the characteristics of clinical patients and symptomatic volunteers.

The cholinergic REM sleep induction test with pilocarpine in mildly depressed patients and normal controls

Previous studies suggested that depressed patients enter rapid-eye movement (REM) sleep more quickly than normal controls following the administration of muscarinic agonists such as arecoline or RS 86. We recently reported that pilocarpine, an orally active muscarinic agonist, induced REM sleep and reduced Stage 3 & 4 (Delta) sleep in young normal volunteers. In this study we present preliminary evidence that pilocarpine had similar effects on REM latency, REM percentage, and Delta (Stages 3 & 4) sleep percentage in depressed patients and controls. Pilocarpine, however, decreased stage-4 sleep in controls more than in depressed patients. Because this group of patients were only mildly depressed at the time of the study, had a high frequency of comorbid substance abuse diagnoses, and had normal electroencephalogram (EEG) sleep patterns under placebo conditions, further studies are necessary to test the hypothesis that depressed patients show hypersensitive cholinergic REM sleep induction.

The cholinergic rapid eye movement induction test with arecoline in depression

The cholinergic rapid eye movement (REM) induction test using arecoline hydrobromide, a cholinergic muscarinic receptor agonist, was studied in patients with affective disorder and in normal controls to determine whether or not depression is associated with enhanced induction of REM sleep by muscarinic agonists. Arecoline induced REM sleep in a dose-dependent fashion in both patients and controls compared with placebo infusions. Compared with normal controls, patients entered REM sleep significantly more rapidly following intravenous administration of 1.0 mg of arecoline hydrobromide than they did following administration of 0.5 mg of arecoline hydrobromide or placebo. These results, as well as those of previous studies, support the hypothesis that patients with affective disorder show a functional supersensitive induction of REM sleep in response to muscarinic receptor agonists and may be consistent with the hypothesis that functional muscarinic receptor "up regulation" is associated with depression.

Effects of the acute administration of caffeine in patients with schizophrenia

Caffeine, 10 mg/kg, was administered to 13 schizophrenic patients in a double-blind placebo-controlled study of its behavioral effects. Some measures of psychopathology were significantly increased: Brief Psychiatric Rating Scale (BPRS) total, BPRS subscales thought disorder, unusual thought content, and euphoria-activation, and several individual BPRS items. Nurses' Bunney-Hamberg ratings of psychosis and mania, comparing the day before with the day after pharmacological challenge, increased significantly. Compared to placebo, caffeine also produced significant increases of diastolic blood pressure and cortisol. Thus, these findings indicate that caffeine increases arousal and has a psychotogenic effect when administered to schizophrenic patients. The possible roles of various neurotransmitters is discussed with special emphasis on caffeine's actions on dopaminergic and adenosinergic systems.