Genetic linkage and association studies in bipolar affective disorder: a time for optimism

Progress and Implications from Genetic Studies of Bipolar Disorder

With the advancements in gene sequencing technologies, including genome-wide association studies, polygenetic risk scores, and high-throughput sequencing, there has been a tremendous advantage in mapping a detailed blueprint for the genetic model of bipolar disorder (BD). To date, intriguing genetic clues have been identified to explain the development of BD, as well as the genetic association that might be applied for the development of susceptibility prediction and pharmacogenetic intervention. Risk genes of BD, such as CACNA1C, ANK3, TRANK1, and CLOCK, have been found to be involved in various pathophysiological processes correlated with BD. Although the specific roles of these genes have yet to be determined, genetic research on BD will help improve the prevention, therapeutics, and prognosis in clinical practice. The latest preclinical and clinical studies, and reviews of the genetics of BD, are analyzed in this review, aiming to summarize the progress in this intriguing field and to provide perspectives for individualized, precise, and effective clinical practice.

Confirmatory test of two factors and four subtypes of bipolar disorder based on lifetime psychiatric co-morbidity

BACKGROUND

The first aim was to use confirmatory factor analysis (CFA) to test a hypothesis that two factors (internalizing and externalizing) account for lifetime co-morbid DSM-IV diagnoses among adults with bipolar I (BPI) disorder. The second aim was to use confirmatory latent class analysis (CLCA) to test the hypothesis that four clinical subtypes are detectible: pure BPI; BPI plus internalizing disorders only; BPI plus externalizing disorders only; and BPI plus internalizing and externalizing disorders.

METHOD

A cohort of 699 multiplex BPI families was studied, ascertained and assessed (1998-2003) by the National Institute of Mental Health Genetics Initiative Bipolar Consortium: 1156 with BPI disorder (504 adult probands; 594 first-degree relatives; and 58 more distant relatives) and 563 first-degree relatives without BPI. Best-estimate consensus DSM-IV diagnoses were based on structured interviews, family history and medical records. MPLUS software was used for CFA and CLCA.

RESULTS

The two-factor CFA model fit the data very well, and could not be improved by adding or removing paths. The four-class CLCA model fit better than exploratory LCA models or post-hoc-modified CLCA models. The two factors and four classes were associated with distinctive clinical course and severity variables, adjusted for proband gender. Co-morbidity, especially more than one internalizing and/or externalizing disorder, was associated with a more severe and complicated course of illness. The four classes demonstrated significant familial aggregation, adjusted for gender and age of relatives.

CONCLUSIONS

The BPI two-factor and four-cluster hypotheses demonstrated substantial confirmatory support. These models may be useful for subtyping BPI disorders, predicting course of illness and refining the phenotype in genetic studies.

Behavioral genetics of affective and anxiety disorders

As shown by clinical genetic studies, affective and anxiety disorders are complex genetic disorders with genetic and environmental factors interactively determining their respective pathomechanism. Advances in molecular genetic techniques including linkage studies, association studies, and genome-wide association studies allow for the detailed dissection of the genetic influence on the development of these disorders. Besides the molecular genetic investigation of categorical entities according to standardized diagnostic criteria, intermediate phenotypes comprising neurobiological or neuropsychological traits (e.g., neuronal correlates of emotional processing) that are linked to the disease of interest and that are heritable, have been proposed to be closer to the underlying genotype than the overall disease phenotype. These intermediate phenotypes are dimensional and more precisely defined than the categorical disease phenotype, and therefore have attracted much interest in the genetic investigation of affective and anxiety disorders. Given the complex genetic nature of affective and anxiety disorders with an interaction of multiple risk genes and environmental influences, the interplay of genetic factors with environmental factors is investigated by means of gene-environment interaction (GxE) studies. Pharmacogenetic studies aid in the dissection of the genetically influenced heterogeneity of psychotropic drug response and may contribute to the development of a more individualized treatment of affective and anxiety disorders. Finally, there is some evidence for genetic factors potentially shared between affective and anxiety disorders pointing to a possible overlapping phenotype between anxiety disorders and depression.

Genetic research into bipolar disorder: the need for a research framework that integrates sophisticated molecular biology and clinically informed phenotype characterization

Research into the genetic basis of bipolar disorder (BD) has reached a turning point. Genome-wide association studies (GWAS), encompassing several thousand samples, have produced replicated evidence for some novel susceptibility genes; however, the genetic variants implicated so far account for only a fraction of disease liability, a phenomenon not limited to psychiatric phenotypes but characteristic of all complex genetic traits studied to date. It appears that pure genomic approaches, such as GWAS alone, will not suffice to unravel the genetic basis of a complex illness like BD. Genomic approaches will need to be complemented by a variety of strategies, including phenomics, epigenomics, pharmacogenomics, and neurobiology, as well as the study of environmental factors. This review highlights the most promising findings from recent GWAS and candidate gene studies in BD. It furthermore sketches out a potential research framework integrating various lines of research into the molecular biological basis of BD.

Ethical considerations in psychiatric genetics

Ethical considerations in psychiatric genetics are highly complex and fluid. This review introduces the reader to the wide range of ethical considerations in this field by examining four characteristics of genetic information. First, genetic information may, to a greater or lesser extent, predict a person's future health. Second, learning about one's genotype may have profound psychosocial consequences. Third, genetic information pertains to a person's biological relatives and thus can affect family members, communities, and population groups. Finally, psychiatric genetics is a rapidly evolving field. None of these characteristics is necessarily "exceptional" or unique to genetics, but they provide a useful framework for teasing apart a complex set of ethical considerations. This article reviews conceptual and empirical data that speak to these four characteristics and then presents a set of conceptual frameworks that can be used to systematically analyze the ethics of psychiatric genetic research and clinical genotyping. Finally, directions for future study are described--including the urgent need to gather data on actual risks and benefits of psychiatric genetic research and clinical applications, so that their utility can be assessed and appropriate ethical safeguards identified.

Genetics of bipolar disorder

Bipolar disorder, especially the most severe type (type I), has a strong genetic component. Family studies suggest that a small number of genes of modest effect are involved in this disorder. Family-based studies have identified a number of chromosomal regions linked to bipolar disorder, and progress is currently being made in identifying positional candidate genes within those regions, À number of candidate genes have also shown evidence of association with bipolar disorder, and genome-wide association studies are now under way, using dense genetic maps. Replication studies in larger or combined datasets are needed to definitively assign a role for specific genes in this disorder. This review covers our current knowledge of the genetics of bipolar disorder, and provides a commentary on current approaches used to identify the genes involved in this complex behavioral disorder.

Will neuroimaging ever be used to diagnose pediatric bipolar disorder?

There is a great need for discovery of biological markers that could be used diagnostically for pediatric onset disorders, particularly those with potentially confusing phenomenology such as pediatric-onset bipolar disorder (BD). Obtaining these markers would help overcome current subjective diagnostic techniques of relying on parent and child interview and symptomatic history. Brain imaging may be the most logical choice for a diagnostic tool, and certain neurobiological abnormalities have already been found in pediatric BD. However, much work remains to be done before neuroimaging can be used reliably to diagnose this disorder, and because of the nature of BD and the limitations of imaging technology and technique, neuroimaging will likely at most be only a diagnostic aide in the near future. In this paper we discuss the characteristics of pediatric BD that complicate the use of biological markers as diagnostic tools, how neuroimaging techniques have been used to study pediatric BD so far, and the limitations and potential of such techniques for future diagnostic use.

Prevention of Pediatric Bipolar Disorder: Integration of Neurobiological and Psychosocial Processes

Bipolar disorder (BD) is a prevalent condition in the United States that typically begins before the age of 18 years and is being increasingly recognized in children and adolescents. Despite great efforts in discovering more effective treatments for BD, it remains a difficult-to-treat condition with high morbidity and mortality. Therefore, it appears prudent to focus energies into developing interventions designed to prevent individuals from ever fully developing BD. Such interventions early in the development of the illness might prevent inappropriate interventions that may worsen or hasten development of BD, delay the onset of first manic episode, and/or prevent development of full BD. Studies of populations at high-risk for BD development have indicated that children with strong family histories of BD, who are themselves experiencing symptoms of attention-deficit/hyperactive disorder (ADHD) and/or depression or have early mood dysregulation, may be experiencing prodromal states of BD. Understanding the neurobiological and genetic underpinnings that create risk for BD development would help with more accurate identification of this prodromal population, which could then lead to suitable preventative interventions. Such interventions could be pharmacologic or psychosocial in nature. Reductions in stress and increases in coping abilities through psychosocial interventions could decrease the chance of a future manic episode. Similarly, psychotropic medications may decrease negative sequelae of stress and have potential for neuroprotective and neurogenic effects that may contribute to prevention of fully expressed BD. Further research into the biologic and environmental mechanisms of BD development as well as controlled early intervention studies are needed to ameliorate this significant public health problem.

Convergent linkage evidence from two Latin-American population isolates supports the presence of a susceptibility locus for bipolar disorder in 5q31-34

We performed a whole genome microsatellite marker scan in six multiplex families with bipolar (BP) mood disorder ascertained in Antioquia, a historically isolated population from North West Colombia. These families were characterized clinically using the approach employed in independent ongoing studies of BP in the closely related population of the Central Valley of Costa Rica. The most consistent linkage results from parametric and non-parametric analyses of the Colombian scan involved markers on 5q31-33, a region implicated by the previous studies of BP in Costa Rica. Because of these concordant results, a follow-up study with additional markers was undertaken in an expanded set of Colombian and Costa Rican families; this provided a genome-wide significant evidence of linkage of BPI to a candidate region of approximately 10 cM in 5q31-33 (maximum non-parametric linkage score=4.395, P<0.00004). Interestingly, this region has been implicated in several previous genetic studies of schizophrenia and psychosis, including disease association with variants of the enthoprotin and gamma-aminobutyric acid receptor genes.

Lack of genetic association between the phospholipase A2 gene and bipolar mood disorder in a European multicentre case-control study

The possible association between phospholipase A2 gene and bipolar mood disorder was examined in 557 bipolar patients and 725 controls (all personally interviewed), recruited from seven countries (Belgium, Bulgaria, Croatia, Germany, Greece, Italy, and UK). The frequencies of the eight alleles that were identified did not differ between patients and control individuals in the whole population, while the power to detect an association based on our sample was relatively high. Some differences were noted among the various ethnic groups, but no significant trends existed, suggesting that population stratification by country may not be responsible for a type II error. On the basis of these results, mutations of the phospholipase A2 gene, at least in the region close to the polymorphism examined between exons 1 and 2, are not involved in the pathogenesis of bipolar mood disorder.

Genome-wide expression analysis detects eight genes with robust alterations specific to bipolar I disorder: relevance to neuronal network perturbation

The limited number of genome-wide transcriptome analyses using the postmortem brains of bipolar disorder sufferers has not produced a clear consensus on the molecular pathways affected by the disorder. To expand the knowledge in this area, we examined the expression levels of more than 12 000 genes in Brodmann's Area (BA), 46 (dorsolateral prefrontal cortex) from bipolar I disorder and control samples using Affymetrix GeneChips. This analysis detected 108 differentially expressed genes in bipolar brains. Validation studies using quantitative RT-PCR on the two original diagnostic cohorts plus tissue from schizophrenic subjects, confirmed the differential expressions of eight genes (RAP1GA1, SST, HLA-DRA, KATNB1, PURA, NDUFV2, STAR and PAFAH1B3) in a bipolar-specific manner and one gene (CCL3) which was downregulated in both bipolar and schizophrenic brains. Of these, protein levels of RAP1GA1 (RAP1 GTPase activating protein 1) showed a trend of increase in BA46 from bipolar brains, in keeping with mRNA transcript levels. Transmission disequilibrium analysis of the nine genes using 43 single nucleotide polymorphisms (SNPs) in 229 National Institute of Mental Health bipolar trios exposed nominal SNP association and modest empirical haplotypic association (P=0.033) between SST (somatostatin) and disease. Finally, gene network analysis using the currently obtained expression data highlighted cellular growth and nervous system development pathways as potential targets in the molecular pathophysiology of bipolar disorder.

Genomewide scan and fine-mapping linkage studies in four European samples with bipolar affective disorder suggest a new susceptibility locus on chromosome 1p35-p36 and provides further evidence of loci on chromosome 4q31 and 6q24

We present the findings of a large linkage study of bipolar affective disorder (BPAD) that involved genomewide analysis of 52 families (448 genotyped individuals) of Spanish, Romany, and Bulgarian descent and further fine mapping of the 1p34-p36, 4q28-q31, and 6q15-q24 regions. An additional sample of 56 German families (280 individuals) was included for this fine-mapping step. The highest nonparametric linkage scores obtained in the fine mapping were 5.49 for 4q31 and 4.87 for 6q24 in the Romany families and 3.97 for 1p35-p36 in the Spanish sample. MOD-score (LOD scores maximized over genetic model parameters) analysis provided significant evidence of linkage to 4q31 and at least borderline significance for the 1p and 6q regions. On the basis of these results and previous positive research findings, 4q31 and 6q24 should now be considered confirmed BPAD susceptibility loci, and 1p35-p36 is proposed as a new putative locus that requires confirmation in replication studies.

Family, twin, adoption, and molecular genetic studies of juvenile bipolar disorder

Juvenile bipolar disorder (JBD) has been a subject of significant research and debate. Phenotypic differences between JBD and adult-onset bipolar disorder have led researchers to question whether or not similar neuropathologic mechanisms will be found. While much is known about the genetic and environmental contributions to the adult-onset phenotype, less is known about their contributions to JBD. Here, we review family, twin, adoption, and molecular genetic studies of JBD. Behavioral genetic data suggest both genetic and environmental contributions to JBD, while molecular genetic studies find linkage to age of onset of bipolar disorder to chromosomes 12p, 14q, and 15q. Additionally, changes associated with symptom age of onset have been recently reported in the brain-derived neurotrophic factor (BDNF) and glycogen synthase kinase 3-beta (GSK3-beta) genes. We contend that further progress in discovering the precise genetic and environmental contributions to JBD may depend on advances in phenotypic refinement, an increased appreciation of comorbid conditions, and more investigation of the longitudinal course of the disorder.

Gene expression and association analyses of LIM (PDLIM5) in bipolar disorder and schizophrenia

We previously reported that expression level of LIM (ENH, PDLIM5) was significantly and commonly increased in the brains of patients with bipolar disorder, schizophrenia, and major depression. Expression of LIM was decreased in the lymphoblastoid cells derived from patients with bipolar disorders and schizophrenia. LIM protein reportedly plays an important role in linking protein kinase C with calcium channel. These findings suggested the role of LIM in the pathophysiology of bipolar disorder and schizophrenia. To further investigate the role of LIM in these mental disorders, we performed a replication study of gene expression analysis and performed genetic association studies. Upregulation of LIM was confirmed in the independent sample set obtained from Stanley Array Collection. No effect of sample pH or medication was observed. Genetic association study revealed the association of single nucleotide polymorphism (SNP)1 (rs10008257) with bipolar disorder. In an independent sample set, SNP2 (rs2433320) close to SNP1 was associated with bipolar disorder. In total samples, haplotype of these two SNPs was associated with bipolar disorder. No association was observed in case-control analysis and family-based association analysis in schizophrenia. These results suggest that SNPs in the upstream region of LIM may confer the genetic risk for bipolar disorder.

No evidence for an association between variants at the proline dehydrogenase locus and schizophrenia or bipolar affective disorder

The proline dehydrogenase locus must be considered as a positional and functional candidate in schizophrenia. It is located in the chromosomal region of the velocardiofacial syndrome on 22q11 that is suspected to contain genes relevant to schizophrenia, and is involved in the metabolism of neurotransmitters. Positive association between single-nucleotide polymorphisms at the proline dehydrogenase locus and schizophrenia further supported the role of proline dehydrogenase in the development of schizophrenia. In order to replicate these findings, we analyzed three single-nucleotide polymorphisms in a sample comprising 299 schizophrenic patients and 300 controls. In addition, we assessed whether proline dehydrogenase also contributes to bipolar affective disorder, because chromosome 22q11 is also implicated in bipolar affective disorder. We therefore included 300 patients with bipolar affective disorder. This is the first study on a potential involvement of the proline dehydrogenase locus in bipolar affective disorder. Neither single marker nor haplotype analysis revealed an association between variants at the proline dehydrogenase locus and schizophrenia or bipolar affective disorder.

Evidence for a relationship between genetic variants at the brain-derived neurotrophic factor (BDNF) locus and major depression

BACKGROUND

Previous genetic studies investigating a possible involvement of variations at the brain derived neurotrophic factor (BDNF) gene locus in major depressive disorder (MDD), bipolar affective disorder (BPAD), and schizophrenia have provided inconsistent results.

METHODS

We performed single-marker and haplotype analyses using three BDNF polymorphisms in 2,376 individuals (465 MDD, 281 BPAD, 533 schizophrenia, and 1,097 control subjects).

RESULTS

Single-marker analysis did not provide strong evidence for association. Haplotype analysis of marker combination rs988748-(GT)n-rs6265 produced nominally significant associations for all investigated phenotypes (global p values: MDD p = .00006, BPAD p = .0057, schizophrenia p = .016). Association with MDD was the most robust finding and could be replicated in a second German sample of MDD patients and control subjects (p = .0092, uncorrected). Stratification of our schizophrenia sample according to the presence or absence of a lifetime history of depressive symptoms showed that our finding in schizophrenia might be attributable mainly to the presence of depressive symptoms.

CONCLUSIONS

Association studies of genetic variants of the BDNF gene with various psychiatric disorders have been published with reports of associations and nonreplications. Our findings suggest that BDNF may be a susceptibility gene for MDD and schizophrenia-in particular, in a subgroup of patients with schizophrenia with a lifetime history of depressive symptoms.

[Alpha-thalassemias and bipolar disorders: a genetic link?]

After a previous paper discussing the possible association between beta-thalassemias and bipolar disorder, this article considers a possible association between alpha-thalassemia and the bipolar disorder. We report the case of a 36 year old woman with bipolar disorder and alpha-thalassemia. The patient, native of Reunion Island, has a family history of bipolar disorder (both parents, one brother, and a paternal uncle). The severity of the bipolar disorder type I in her family, is illustrated by the suicides of both parents, one brother and the paternal uncle, in intervals of only a few years. After a Medline review (1980-2004) we found only two studies suggesting a possible relationship between bipolar disorders and alpha-thalassemias, but without clinical case report information. Some genetic studies described the existence of possible genetic susceptibility for bipolar disorder on the short arm of chromosome 16, close to the gene involved in certain alpha-thalassemias, on the region 16p13.3. An interesting finding is that the sequencing of 258 kb of the chromosome region 16p13.3 not only allowed the identification of genes involved in the alpha-thalassemia and in the vulnerability to bipolar disorders, but also the identification of genes implicated in tuberous sclerosis, in polycystic kidney disease, in cataract with microophtalmia, and in vulnerability genetic factors for ATR-16 syndrome, asthma, epilepsy, certain forms of autism and mental retardation. Numerous clinical descriptions and some familial studies on linkage suggested a possible relationship between tuberous sclerosis, polycystic kidney disease, cataract with microophtalmia, ATR-16 syndrome, asthma, epilepsy, certain forms of autism, mental retardation and bipolar disorder, given the closeness of these vulnerability genes on the short arm of the chromosome 16. A vulnerability gene of alcohol dependence was also identified on this same chromosome region (16p13.3), by a study concerning 105 families. Taking into account the methodological difficulties due to the clinical and genetic heterogeneity of bipolar disorder, we suggest that linkage techniques should be used to confirm the presence of susceptibility genetic factor for bipolar disorders on chromosome 16. Thus a known genetic disease (alpha-thalassemia) could contribute to confirming the presence on the short arm of chromosome 16 of a susceptibility genetic factor for bipolar disorders. Linkage studies should be performed in families with a strong association for both diseases. Thanks to linkage techniques, one could hope for an improvement in understanding the physiopathology of bipolar disorder, with possible implications at a therapeutic level.

Neuropsychological dysfunction in bipolar affective disorder: a critical opinion

Data from the imaging literature have led to suggestions that permanent structural brain changes may be associated with bipolar disorder. Individuals diagnosed with bipolar disorder display deficits on a range of neuropsychological tasks in both the acute and euthymic phases of illness, and correlations between experienced number of affective episodes and task performance are commonly reported. These findings have renewed interest in the neuropsychological profile of individuals with bipolar disorder, with deficits of attention, learning and memory, and executive function, asserted to be present. This paper critically reviews five different potential causes of neurocognitive dysfunction in bipolar disorder: (i) iatrogenic, (ii) acute functional changes associated with depression or mania, (iii) permanent structural lesions of a neurodegenerative origin, (iv) permanent structural lesions that are neurodevelopmental in origin, and (v) permanent functional changes that are most likely genetic in origin. Although the potential cognitive effects of residual symptomatology and long-term medication use cannot be entirely excluded, we conclude that functional changes associated with genetically driven population variation in critical neural networks underpin both the neurocognitive and affective symptoms of bipolar disorder. The philosophical implications of this conclusion for neuropsychology are briefly discussed.

Principles of haplotype mapping and potential applications to attention-deficit/hyperactivity disorder

Approaches to the study of common, complex genetic disorders like attention-deficit/hyperactivity disorder (ADHD) are evolving rapidly. Traditional linkage and association mapping each have distinct roles to play. Rapid advances in genomic information and technologies make association studies more attractive, including the possibility in the near future of whole genome association scans. This review covers the following broad topics: 1) the principles of linkage and association analyses as they apply to ADHD, and 2) the implications of genome architecture for association studies of complex diseases like ADHD. The structure of linkage disequilibrium is approached through review of the statistical measures of allelic associations and their relationship to observed haplotypes. The patterns of haplotypes across the human genome are discussed, as well as the implications of linkage disequilibrium mapping for association studies in general and ADHD specifically. Finally, the extent to which the allelic architecture of a candidate ADHD gene is publicly available and the web resources to access this information are covered. Today, the wealth of polymorphism data available on the worldwide web enables researchers to focus powerful methodologic tools on candidate genes and regions of interest. Coupling this with larger patient collections and more refined phenotyping will move forward the identification of disease-associated polymorphisms and ultimately the development of genetically based pharmaceuticals and diagnostic tests.

Recent findings on the genetic basis of bipolar disorder

What began as a search for a specific gene for bipolar disorder has now become a search for multiple susceptibility genes as it has be-come clear that the genetic basis of bipolar disorder probably involves multiple genes interacting with each other and with environmental components in as-yet mysterious ways. This article reviews the most recent findings and the emerging picture in the genetics of bipolar disorder.

The power of sample size and homogenous sampling: association between the 5-HTTLPR serotonin transporter polymorphism and major depressive disorder

BACKGROUND

Several lines of evidence indicate that abnormalities in the functioning of the central serotonergic system are involved in the pathogenesis of affective illness. A 44-base-pair insertion/deletion polymorphism in the 5' regulatory region of the serotonin transporter gene (5-HTTLPR), which influences expression of the serotonin transporter, has been the focus of intensive research since an initial report on an association between 5-HTTLPR and depression-related personality traits. Consistently replicated evidence for an involvement of this polymorphism in the etiology of mood disorders, particularly in major depressive disorder (MDD), remains scant.

METHODS

We assessed a potential association between 5-HTTLPR and MDD, using the largest reported sample to date (466 patients, 836 control subjects). Individuals were all of German descent. Patients were systematically recruited from consecutive inpatient admissions. Control subjects were drawn from random lists of the local Census Bureau and screened for psychiatric disorders.

RESULTS

The short allele of 5-HTTLPR was significantly more frequent in patients than in control subjects (45.5% vs. 39.9%; p = .006; odds ratio = 1.26).

CONCLUSIONS

These results support an involvement of 5-HTTLPR in the etiology of MDD. They also demonstrate that the detection of small genetic effects requires very large and homogenous samples.

Molecular genetics of affective disorders

Evidence for familial aggregation in Affective Disorders (AD) has been provided in classical studies. Linkage and association genetic studies have been proposed to detect genetic factors implicated in AD. However, findings from molecular genetic studies remain inconclusive. Nevertheless, current research is focusing on the phenotypes, both sub- and endophenotypes. In addition, recent advances in technology, such as microarrays, provide new tools in psychiatric genetics. These different approaches offer a new optimism era in the search of genetic factors in AD.

Emerging experimental therapeutics for bipolar disorder: clues from the molecular pathophysiology

Bipolar affective disorder (manic-depressive illness) is a common, severe, chronic, and often life-threatening illness, associated with significant comorbidity. The recognition of the significant morbidity and mortality of patients with bipolar disorder, as well as the growing appreciation that a high percentage of patients respond poorly to existing treatments, has made the task of discovering new therapeutic agents, that are both efficacious and have few side effects increasingly more important. Most recent agents introduced into the pharmacopeia for the treatment of bipolar disorder have been anticonvulsants and atypical antipsychotics. We propose that novel treatments developed specifically for bipolar disorder will arise from (1) understanding more precisely the molecular mechanisms of treatments that are clearly efficacious or (2) developing medications based on the knowledge obtained of the underlying pathophysiology of bipolar disorder. Knowledge with regard to the underlying pathophysiology of bipolar disorder is increasing at a rapid pace, including alterations in intracellular signaling cascades as well as impairments of cellular plasticity and resilience in critical neuronal circuits. We propose that therapeutics designed to enhance cellular plasticity and resilience and that counter maladaptive stress-responsive systems may have considerable utility for the treatment of bipolar disorder. Therapeutic strategies designed to address cellular resilience and plasticity include the regulation of neurotrophic pathways, glucocorticoid signaling, phosphodiesterase activity, and glutamatergic throughput and mitochondrial function. While the task of developing novel medications for bipolar disorder is truly daunting, these and similar approaches will ultimately lead to better medications for the millions who suffer from this devastating illness.