Informing DSM-5: biological boundaries between bipolar I disorder, schizoaffective disorder, and schizophrenia
© Cosgrove and Suppes; licensee BioMed Central Ltd. 2013
Received: 8 February 2013
Accepted: 19 April 2013
Published: 14 May 2013
The fifth version of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) opted to retain existing diagnostic boundaries between bipolar I disorder, schizoaffective disorder, and schizophrenia. The debate preceding this decision focused on understanding the biologic basis of these major mental illnesses. Evidence from genetics, neuroscience, and pharmacotherapeutics informed the DSM-5 development process. The following discussion will emphasize some of the key factors at the forefront of the debate.
Family studies suggest a clear genetic link between bipolar I disorder, schizoaffective disorder, and schizophrenia. However, large-scale genome-wide association studies have not been successful in identifying susceptibility genes that make substantial etiological contributions. Boundaries between psychotic disorders are not further clarified by looking at brain morphology. The fact that symptoms of bipolar I disorder, but not schizophrenia, are often responsive to medications such as lithium and other anticonvulsants must be interpreted within a larger framework of biological research.
For DSM-5, existing nosological boundaries between bipolar I disorder and schizophrenia were retained and schizoaffective disorder preserved as an independent diagnosis since the biological data are not yet compelling enough to justify a move to a more neurodevelopmentally continuous model of psychosis.
KeywordsBipolar disorder Hallucinations Delusions Schizoaffective disorder Schizophrenia DSM- 5 Genes Psychiatric medication Brain function
Schizophrenia, which occurs in approximately 1% of the population, may be characterized by dramatic symptoms of delusions and hallucinations, affective flattening and amotivation, or negative symptoms. While individuals with schizophrenia may need ongoing support to maintain themselves independently, recovery initiatives have demonstrated that achievement of personal or professional goals and expansion of self-concept are attainable for individuals with schizophrenia [8, 9]. By comparison, BD I occurs in about 1% of the population and is notable for its episodic nature with severe but periodic symptoms of mania and depression. A common manic presentation includes reports of minimal sleep accompanied by increased energy, changes in mood and judgment, and impulsivity. About 50% of manic episodes contain psychotic elements such as grandiosity, frank delusions and hallucinations, or paranoia . Even in cases where manic episodes manifest psychotic content, many individuals may be responsive to medications and essentially return to full functioning with ongoing treatment. Schizoaffective disorder, estimated to occur in less than 1% of the population, appears to represent a midpoint on the pathologic spectrum between BD I and schizophrenia with psychotic symptoms predominant and mood symptoms of mania and depression less evident (see Figure 1) [11, 12]. Individuals meeting criteria for this diagnosis report at least a two-week period without evidence of mood instability and persistent psychotic symptoms. In the DSM-IV TR categorization scheme, schizoaffective disorder includes both psychotic symptoms and severe mood episodes; however, by definition, there must be periods of psychosis without any disturbance in mood.
Hallucinations and delusions are typically considered the hallmark of schizophrenia and mood fluctuations central to BD I; however, psychotic symptoms may be present in both. Although bipolar mood episodes may have an inherent episodic rhythm, schizophrenia, schizoaffective disorder, and BD I can all be chronic, lifelong conditions that cause significant functional impairment.
Since both psychosis and mood disturbance may constitute core features of schizophrenia, BD I, and schizoaffective disorder, a debate arose during the early pre-DSM-5 development process about the idea of merging diagnoses in the revised manual . A substantial body of research has focused on the genetic and neuroscientific etiological mechanisms of psychosis given that symptoms occur in schizophrenia in addition to schizoaffective disorder and BD I, among other psychiatric illnesses (major depression not being considered here) [13–15]. The argument in favor of merging diagnostic entities is based, in part, on the idea that schizoaffective disorder has proven to be a challenging differential diagnosis in clinical realms. Its diagnostic reliability across both clinicians and treatment settings is poor, and data promoting effective schizoaffective disorder-specific treatments are very limited .
Our aim in this paper is to first briefly and concisely review existing lines of biological evidence from behavioral and molecular genetics, neuroscience, and psychopharmacotherapeutics in order to determine whether they support or refute the idea of merging diagnoses involving psychosis in DSM-5. Given that DSM-5 has chosen to retain DSM-IV-TR’s operative criteria for BD I, schizoaffective disorder, and schizophrenia, the subsequent discussion will in part emphasize some of the key factors that may have informed the decision to sustain separation of nosologic and diagnostic criteria for BD I, schizoaffective disorder, and schizophrenia. Revisions in DSM-5 to all psychiatric diagnoses were made only after balancing tensions in creating a manual of psychiatric nosology that both adheres to the medical model of psychiatry  and is at once accurate, useful, and contemporary [17–20].
It is helpful to consider competing nosological models involving mood and psychotic disorders before attempting to critically evaluate biological evidence. Kraepelin’s dichotomous classification of psychosis into dementia praecox and manic-depressive insanity has informed earlier iterations of the DSM . However, the National Institute of Mental Health’s (NIMH’s) Research Domain Criteria, or RDoC, may be a more useful lens through which to examine data linking biology and behavior in psychosis . The RDoC framework purports a full spectrum, neurodevelopmentally continuous model for understanding psychiatric illness that is dimensional in nature and encourages assessment of behavior at genetic, molecular, cellular, and physiological levels. In other words, RDoC is a way to digest the relatively common findings that risk genes for one psychiatric disorder are associated with risk for many psychiatric disorders or that similar changes in brain structure or function are observed in many psychiatric disorders .
Summary of key evidence at the forefront of the boundaries of schizophrenia, schizoaffective disorder, and bipolar I disorder debate
Increased risk for bipolar disorder in families of individuals with schizophrenia and for schizophrenia in families of individuals with bipolar disorder
Schizophrenia and bipolar disorder linked to unipolar depression
Kendler et al., 1998 
Roscommon Family Study; vulnerability to psychosis may extend across schizophrenia, major depression, and bipolar disorder
Cardno et al., 2002 
Significant genetic correlations between schizophrenia, schizoaffective disorder, and mania
Genome wide association studies (GWAS)
ZNF804A and CACNA1C may influence risk for both schizophrenia and bipolar disorder
Some overlapping white and gray matter deficits, but cortical reductions exclusive to schizophrenia
McIntosh et al., 2006 
Genetic liability for gray matter reductions in DLPRC and VLPFC exclusively in schizophrenia
Hulshoff et al., 2012 
Overlapping white matter volume and areas of thin cortex suggest shared neurodevelopment
Lithium can be used as monotherapy or for augmentation of antipsychotics in bipolar disorder but ineffective in schizophrenia
Casey et al., 2003 
Divalproex prescribed for acute mania but minimal efficacy in schizophrenia
Initial reports of lamotrigine positive in add-on schizophrenia, but no better than placebo in multicenter, randomized trials
Post et al., 1999 
Unexpected broad efficacy across psychotic disorders for second generation antipsychotics
Strength of evidence for biological factors supporting merging in some way schizophrenia, schizoaffective and bipolar I disorder
Strength of evidence
Pharmacotherapeutics—lithium, divalproex, lamotrigine, antipsychotics
Genetic investigations offer a unique vantage point from which to consider the shared etiology of psychotic disorders. Aggregation within families of both schizophrenia and bipolar disorder has long been proposed as proof for continuity between the two disorders, and indeed its evidence spans multiple decades and is strong. Bipolar disorder, it seems, occurs more frequently than expected by chance in families of affected individuals and vice versa [26, 29, 30]. This same finding is observed in entire nations. Two large and important population-based studies—one based on data from the Danish Civil Registration System  and the other from the multi-generation and hospital-based registers in Sweden  both concluded that first-degree relatives of individuals with bipolar disorder were at higher risk for schizophrenia as well as bipolar disorder in several million families.
Twin studies provide further insight. Since monozygotic twins share 100% of their genes but dizygotic twins only 50%, on average, behavioral differences between the two can largely be attributed to environmental influences. The Maudsley Twin Registry studies are the only scientific investigation specifically focused on disentangling the genetic and environmental influences on different types of psychosis . Findings confirm a shared genetic liability between psychosis in schizophrenia, schizoaffective disorder, and bipolar I mania. Additionally, genetic contributions to schizoaffective disorder appear to be entirely shared with those contributing to schizophrenia and mania, shedding substantial doubt on the accuracy of an independent schizoaffective disorder diagnosis .
Given the robust evidence of shared genetic etiology between schizophrenia and bipolar disorder amassed from family studies, a ‘hopeful’ energy drove the search for specific candidate genes related to psychosis in the late 1990s and early 2000s. However, this exploration—first using single-gene association methodology and later, genome-wide association studies (GWAS)—has proven difficult and largely yielded disappointing and inconclusive findings . It has not been challenging to identify genetic variants common to both schizophrenia-spectrum and bipolar disorders; however, their relative etiological contributions seem to be very small. In recent years, two risk genes have repeatedly emerged as critical and common to psychosis in both disorders. First, an intron of zinc finger binding protein 804A (ZNF804A) on chromosome 6, a protein sequence potentially involved in brain connectivity, has been implicated. Based on odds ratios, ZNF804A appears to act as a susceptibility site for psychosis although its contribution is likely very small [14, 37]. Second, an intron of the L-type voltage dependent calcium channel alpha 1C subunit (CACNA1 C), potentially involved in neuronal calcium-dependent processes, has also repeatedly been identified as a gene conferring a small but detectable increased risk in both schizophrenia and bipolar disorder 
One glaring criticism of many genetic investigations has been that very few make a phenotypic distinction between psychotic and non-psychotic BD I when making comparisons with schizophrenia. For example, Green and colleagues  report that 66% of their bipolar disorder cases endorsed a positive history of psychotic symptoms; however, their subsequent genetic analyses involving CACNA1 C do not differentiate this subgroup. Since psychotic symptoms occur generally in about 50% of manic episodes of BDI, it is difficult to know whether a susceptibility locus such as CACNA1 C confers risk for psychosis or other features shared between the two disorders (that is., anhedonia, cognitive impairment, and so on).
Evidence from investigations of brain morphology does little to clarify the boundaries between various psychotic disorders. Rather, it seems that in addition to some disorder-specific changes, psychosis occurring as a result of BD I or schizophrenia appears to be related to patterns of morphological changes in brain regions that seem to be involved in both of these disorders . While reductions in cortical volume and thickness appear to be specific for schizophrenia, and not BD I , decreases in total brain mass have been reported in both disorders . Further, consonant gray matter reductions in paralimbic regions including the anterior cingulate and insula, thought to be involved in emotional processing, have been observed in schizophrenia and bipolar disorder . Again, none of these studies differentiates between psychotic and non-psychotic BD I, and some even fail to differentiate between bipolar I and bipolar II, a form of the illness not involving manic episodes and with less psychotic burden of these disorders.
Combining family-based behavioral genetic methodologies with brain morphometry techniques has led to findings that in part point to shared biological origins, although there remains confusion. While two recent studies suggest that prefrontal cortical grey matter reductions  and reduced hippocampal volumes  may be correlated to increased genetic susceptibility to schizophrenia but not BD I, others suggest shared genetic liabilities for potentially pathognomic factors that may affect differing brain regions and networks. McDonald and colleagues observed that both schizophrenia and bipolar disorder were related to white matter deficits in overlapping regions of the brain but that deficits in grey matter appeared in completely separate regions . It is worth noting that their sample of individuals with bipolar disorder consisted only of those who had experienced psychotic symptoms. By far, the most convincing evidence linking genetic susceptibility and brain structure was reported in a recent twin study of monozygotic and dizygotic twin pairs concordant or discordant for schizophrenia or bipolar disorder . Absence of psychosis was not exclusionary, but genetic liability for both disorders was associated with reduction in white matter volume as well as thinner areas of the cortex in similar areas of the brain.
Response patterns to medication across different psychiatric diagnostic categories are complex. There is more than one clear case, for example, of medications being fully effective to treat all symptoms including mania and psychosis for BD I and ineffective to treat patients with schizophrenia or schizoaffective disorder. As well, individuals exhibiting the same diagnostic profile and with similar presenting symptoms may respond differently to the same medications. There are still too few clear guideposts to predict optimal treatment response. Psychophamacological response data interpreted in isolation are inherently inferential in nature and thus, must be comprehended with caution. Interpretation must be integrated within a larger framework of research that defines underlying mediators or moderators of treatment response, such as behavioral or molecular genetic profiles, neuroanatomy or brain functioning. Importantly, in this section we have elected to discuss clinically observed and studied impacts of medications in broad use that highlight differences across current diagnostic categories. We will not discuss cellular receptor differences between these different medications as these are beyond the scope of this manuscript. For review and discussion of purported medication mechanisms, we refer you to Steven Stahl’s Essential Psychopharmacology work .
One such example of different response patterns across psychotic disorders is lithium, approved by the Food and Drug Administration (FDA) in 1971 for treatment of mania and soon afterward considered a first-line treatment for bipolar disorder . Despite clear strong effectiveness studies in BD I, lithium utilized as monotherapy or as augmentation of antipsychotic medication for individuals with schizophrenia appears to be largely ineffective [61, 62]. A pivotal study analyzing recurrence of bipolar episodes following discontinuation of lithium maintenance treatment demonstrated that patients relapsed into mania or depression more quickly following lithium discontinuation than the individual’s normal course of illness might predict . In other words, patients with bipolar disorder tend to show ‘rebound’ effects from abrupt discontinuation of lithium whereas patients with schizophrenia treated with lithium do not .
Divalproex, an anticonvulsant, was introduced by the FDA in 1995 for treatment of BD I mania. Similar to lithium, divalproex has minimal benefit in the treatment of schizophrenia or schizoaffective disorder. In combination with olanzapine and risperidone, divalproex resulted in an accelerated, initial decrease in psychotic symptoms . However, a recent Cochrane analysis concluded that there were no available data to substantiate the use of divalproex as monotherapy in schizophrenia .
Response to lamotrigine in different psychotic disorders is also pertinent to a discussion about potentially merging schizophrenia and BD I. Lamotrigine was approved by the FDA in 2003 for the prevention of new episodes of mania or depression in BD I . Although early reports of adjunctive use of lamotrigine to treat schizophrenia were positive , it was, in fact, shown to be no more efficacious than placebo (as an add-on agent) in two recently conducted trials .
Finally, the use of both typical and second generation (atypical) antipsychotics in the treatment of various psychotic disorders should be considered. From the 1960s to 1980s, before lithium was approved by the FDA and widely used, typical antipsychotics, such as haloperidol or fluphenazine, were generally regarded as the only available first-line medications for the treatment of mania . Some evidence suggests that patients with BD I treated with typical antipsychotics may be more sensitive to serious side effect profiles including neuroleptic malignant syndrome than patients with schizophrenia . Because of unexpected, broad effectiveness and—at least before potential metabolic side effects were noted—comparably favorable side effect profiles, second generation antipsychotics are frequent choices in schizophrenia, schizoaffective disorder, and BD I. At a minimum, all work reasonably well as antipsychotic agents in treating these disorders, despite acting across a range of receptor systems (for example, serotonin, dopaminergic, and so on), and having heterogenous side effect profiles.
With regard to DSM-5, the biological data are not yet compelling enough to warrant embracing a more neurodevelopmentally continuous model of psychosis consistent with RDoC and not yet strong enough on their own to currently warrant a radical change to psychiatric nosology, such as merging schizophrenia and psychotic BD I. For DSM-5, existing nosological boundaries between the two were retained and schizoaffective disorder preserved as an independent diagnosis. While a shared genetic liability among psychotic disorders is likely, the real biological evidence still largely stems from family studies and is not routinely supported by candidate gene or GWAS investigations. It is still not possible to make a definitive statement about what genes are primarily responsible for this genetic risk, since confirming roles for putative genes has not panned out on a molecular level in the way behavioral geneticists had hoped. GWAS findings have demonstrated likely small roles for ZNF804A and CACNA1 C; however, mechanistically these are not well understood.
Response to medication, an area of extensive research, indicates we do not yet understand the biological basis of these illnesses. Some researchers consider psychotic phenomena to be epiphenomena to the primary illness. Thus, under this idea, lithium treats the underlying condition in BD I, resolving psychotic manic symptoms, but is ineffective in schizophrenia given its inability to treat the underlying pathophysiology of this illness.
Even after linking genetic risk to both disorders with structural changes in the brain and considering response to psychotropic medications, the biological evidence falls short of the requisite durability necessary to warrant a DSM-5 change that will likely command diagnosis in both clinical practice and research investigations for at least a decade to come.
Still, in spite of the shortcomings of the existing biological evidence, an RDoC-inspired model for psychosis integrating evidence from multiple modalities seems probable for DSM revisions of the future. To what extent these lines of evidence will influence future psychiatric nosology depends largely on how our understanding of brain function changes as science advances. As technology develops, it is to be hoped it will become easier and cheaper to investigate the complex alliances between brain circuits and genes that lead to the neurodevelopment of psychosis. Clear, replicable phenotyping of illness characteristics will be most critical to these efforts.
- BD I:
bipolar I disorder
Diagnostic and Statistical Manual of Mental Disorders, 5th edition
Food and Drug Administration
genome wide association studies
research domain criteria.
- Deconstructing Psychosis: Refining the Research Agenda for DSM-V. Edited by: Tamminga CA, Sirovatka PJ, Regier DA, Os J van. 2010, Arlington, VA: American Psychiatric Association
- Kendler KS: An historical framework for psychiatric nosology. Psychol Med. 2009, 39: 1935-1941. 10.1017/S0033291709005753.View ArticlePubMedPubMed CentralGoogle Scholar
- Kawa S, Giordano J: A brief historicity of the Diagnostic and Statistical Manual of Mental Disorders: issues and implications for the future of psychiatric canon and practice. Philos Ethics Humanit Med. 2012, 7: 2-10.1186/1747-5341-7-2.View ArticlePubMedPubMed CentralGoogle Scholar
- Patil T, Giordano J: On the ontological assumptions of the medical model of psychiatry: philosophical considerations and pragmatic tasks. Philos Ethics Humanit Med. 2010, 5: 3-10.1186/1747-5341-5-3.View ArticlePubMedPubMed CentralGoogle Scholar
- Farah MJ, Gillihan SJ: The puzzle of neuroimaging and psychiatric diagnosis: technology and nosology in an evolving discipline. AJOB Neurosci. 2012, 3: 31-41.View ArticlePubMedPubMed CentralGoogle Scholar
- Robins E, Guze SB: Establishment of diagnostic validity in psychiatric illness: its application to schizophrenia. Am J Psychiatry. 1970, 126: 983-987.View ArticlePubMedGoogle Scholar
- Radden JH: Recognition rights, mental health consumers and reconstructive cultural semantics. Philos Ethics Humanit Med. 2012, 7: 6-10.1186/1747-5341-7-6.View ArticlePubMedPubMed CentralGoogle Scholar
- Silverstein SM, Bellack AS: A scientific agenda for the concept of recovery as it applies to schizophrenia. Clin Psychol Rev. 2008, 28: 1108-1124. 10.1016/j.cpr.2008.03.004.View ArticlePubMedGoogle Scholar
- Lysaker PH, Roe D, Buck KD: Recovery and wellness amidst schizophrenia: definitions, evidence, and the implications for clinical practice. J Am Psychiatr Nurses Assoc. 2010, 16: 36-42. 10.1177/1078390309353943.View ArticlePubMedGoogle Scholar
- Rosen LN, Rosenthal NE, Dunner DL, Fieve RR: Social outcome compared in psychotic and nonpsychotic bipolar I patients. J Nerv Ment Dis. 1983, 171: 272-275. 10.1097/00005053-198305000-00002.View ArticlePubMedGoogle Scholar
- Abrams DJ, Rojas DC, Arciniegas DB: Is schizoaffective disorder a distinct categorical diagnosis? A critical review of the literature. Neuropsychiatr Dis Treat. 2008, 4: 1089-1109.View ArticlePubMedPubMed CentralGoogle Scholar
- Malhi GS, Green M, Fagiolini A, Peselow ED, Kumari V: Schizoaffective disorder: diagnostic issues and future recommendations. Bipolar Disord. 2008, 10: 215-230. 10.1111/j.1399-5618.2007.00564.x.View ArticlePubMedGoogle Scholar
- Ivleva EI, Morris DW, Moates AF, Suppes T, Thaker GK, Tamminga CA: Genetics and intermediate phenotypes of the schizophrenia–bipolar disorder boundary. Neurosci Biobehav Rev. 2010, 34: 897-921. 10.1016/j.neubiorev.2009.11.022.View ArticlePubMedGoogle Scholar
- O’Donovan MC, Craddock NJ, Owen MJ: Genetics of psychosis; insights from views across the genome. Hum Genet. 2009, 126: 3-12. 10.1007/s00439-009-0703-0.View ArticlePubMedGoogle Scholar
- Gur RE, Keshavan MS, Lawrie SM: Deconstructing psychosis with human brain imaging. Schizophr Bull. 2007, 33: 921-931. 10.1093/schbul/sbm045.View ArticlePubMedPubMed CentralGoogle Scholar
- Jäger M, Haack S, Becker T, Frasch K: Schizoaffective disorder–an ongoing challenge for psychiatric nosology. Eur Psychiatry. 2011, 26: 159-165.View ArticlePubMedGoogle Scholar
- Phillips J, Frances A, Cerullo MA, Chardavoyne J, Decker HS, First MB, Ghaemi N, Greenberg G, Hinderliter AC, Kinghorn WA, LoBello SG, Martin EB, Mishara AL, Paris J, Pierre JM, Pies RW, Pincus HA, Porter D, Pouncey C, Schwartz MA, Szasz T, Wakefield JC, Waterman GS, Whooley O, Zachar P: The six most essential questions in psychiatric diagnosis: a pluralogue part 1: conceptual and definitional issues in psychiatric diagnosis. Philos Ethics Humanit Med. 2012, 7: 3-10.1186/1747-5341-7-3.View ArticlePubMedPubMed CentralGoogle Scholar
- Phillips J, Frances A, Cerullo MA, Chardavoyne J, Decker HS, First MB, Ghaemi N, Greenberg G, Hinderliter AC, Kinghorn WA, LoBello SG, Martin EB, Mishara AL, Paris J, Pierre JM, Pies RW, Pincus HA, Porter D, Pouncey C, Schwartz MA, Szasz T, Wakefield JC, Waterman GS, Whooley O, Zachar P: The six most essential questions in psychiatric diagnosis: a pluralogue part 2: Issues of conservatism and pragmatism in psychiatric diagnosis. Philos Ethics Humanit Med. 2012, 7: 8-10.1186/1747-5341-7-8.View ArticlePubMedPubMed CentralGoogle Scholar
- Phillips J, Frances A, Cerullo MA, Chardavoyne J, Decker HS, First MB, Ghaemi N, Greenberg G, Hinderliter AC, Kinghorn WA, LoBello SG, Martin EB, Mishara AL, Paris J, Pierre JM, Pies RW, Pincus HA, Porter D, Pouncey C, Schwartz MA, Szasz T, Wakefield JC, Waterman GS, Whooley O, Zachar P: The six most essential questions in psychiatric diagnosis: a pluralogue part 3: issues of utility and alternative approaches in psychiatric diagnosis. Philos Ethics Humanit Med. 2012, 7: 9-10.1186/1747-5341-7-9.View ArticlePubMedPubMed CentralGoogle Scholar
- Phillips J, Frances A, Cerullo MA, Chardavoyne J, Decker HS, First MB, Ghaemi N, Greenberg G, Hinderliter AC, Kinghorn WA, LoBello SG, Martin EB, Mishara AL, Paris J, Pierre JM, Pies RW, Pincus HA, Porter D, Pouncey C, Schwartz MA, Szasz T, Wakefield JC, Waterman GS, Whooley O, Zachar P: The six most essential questions in psychiatric diagnosis: a pluralogue. Part 4: general conclusion. Philos Ethics Humanit Med. 2012, 7: 14-10.1186/1747-5341-7-14.View ArticlePubMedPubMed CentralGoogle Scholar
- Kraepelin E: Psychiatrie. 1899, Leipzig: Barth, 6Google Scholar
- Insel T, Cuthbert B, Garvey M, Heinssen R, Pine DS, Quinn K, Sanislow C, Wang P: Research domain criteria (RDoC): toward a new classification framework for research on mental disorders. Am J Psychiatry. 2010, 167: 748-751. 10.1176/appi.ajp.2010.09091379.View ArticlePubMedGoogle Scholar
- Caspi A, Moffitt TE: Gene-environment interactions in psychiatry: joining forces with neuroscience. Nat Rev Neurosci. 2006, 7: 583-590.View ArticlePubMedGoogle Scholar
- Wurzman R, Giordano J: Differential susceptibility to plasticity: a ‘missing link’ between gene-culture co-evolution and neuropsychiatric spectrum disorders?. BMC Med. 2012, 10: 37-10.1186/1741-7015-10-37.View ArticlePubMedPubMed CentralGoogle Scholar
- Belsky J, Pluess M: Beyond diathesis stress: differential susceptibility to environmental influences. Psychol Bull. 2009, 135: 885-908.View ArticlePubMedGoogle Scholar
- Tsuang MT, Winokur G, Crowe RR: Morbidity risks of schizophrenia and affective disorders among first degree relatives of patients with schizophrenia, mania, depression and surgical conditions. Br J Psychiatry. 1980, 137: 497-504. 10.1192/bjp.137.6.497.View ArticlePubMedGoogle Scholar
- Mortensen PB, Pedersen CB, Melbye M, Mors O, Ewald H: Individual and familial risk factors for bipolar affective disorders in Denmark. Arch Gen Psychiatry. 2003, 60: 1209-1215. 10.1001/archpsyc.60.12.1209.View ArticlePubMedGoogle Scholar
- Lichtenstein P, Yip BH, Björk C, Pawitan Y, Cannon TD, Sullivan PF, Hultman CM: Common genetic determinants of schizophrenia and bipolar disorder in Swedish families: a population-based study. Lancet. 2009, 373: 234-239. 10.1016/S0140-6736(09)60072-6.View ArticlePubMedGoogle Scholar
- Van Snellenberg JX, De Candia T: Meta-analytic evidence for familial coaggregation of schizophrenia and bipolar disorder. Arch Gen Psychiatry. 2009, 66: 748-755. 10.1001/archgenpsychiatry.2009.64.View ArticlePubMedGoogle Scholar
- Dean K, Stevens H, Mortensen PB, Murray RM, Walsh E, Pedersen CB: Full spectrum of psychiatric outcomes among offspring with parental history of mental disorder. Arch Gen Psychiatry. 2010, 67: 822-829. 10.1001/archgenpsychiatry.2010.86.View ArticlePubMedGoogle Scholar
- Gershon ES, Hamovit J, Guroff JJ, Dibble E, Leckman JF, Sceery W, Targum SD, Nurnberger JI, Goldin LR, Bunney WE: A family study of schizoaffective, bipolar I, bipolar II, unipolar, and normal control probands. Arch Gen Psychiatry. 1982, 39: 1157-10.1001/archpsyc.1982.04290100031006.View ArticlePubMedGoogle Scholar
- Maier W, Lichtermann D, Minges J, Hallmayer J, Heun R, Benkert O, Levinson DF: Continuity and discontinuity of affective disorders and schizophrenia. Results of a controlled family study. Arch Gen Psychiatry. 1993, 50: 871-10.1001/archpsyc.1993.01820230041004.View ArticlePubMedGoogle Scholar
- Kendler KS, Karkowski LM, Walsh D: The structure of psychosis: latent class analysis of probands from the Roscommon Family Study. Arch Gen Psychiatry. 1998, 55: 492-499. 10.1001/archpsyc.55.6.492.View ArticlePubMedGoogle Scholar
- Cardno AG, Rijsdijk FV, Sham PC, Murray RM, McGuffin P: A twin study of genetic relationships between psychotic symptoms. Am J Psychiatry. 2002, 159: 539-545. 10.1176/appi.ajp.159.4.539.View ArticlePubMedGoogle Scholar
- Green EK, Grozeva D, Jones I, Jones L, Kirov G, Caesar S, Gordon-Smith K, Fraser C, Forty L, Russell E, Hamshere ML, Moskvina V, Nikolov I, Farmer A, McGuffin P, Holmans PA, Owen MJ, O'Donovan MC, Craddock N: The bipolar disorder risk allele at CACNA1C also confers risk of recurrent major depression and of schizophrenia. Mol Psychiatry. 2009, 15: 101698.Google Scholar
- Williams HJ, Craddock N, Russo G, Hamshere ML, Moskvina V, Dwyer S, Smith RL, Green E, Grozeva D, Holmans P, Owen MJ, O'Donovan M: Most genome-wide significant susceptibility loci for schizophrenia and bipolar disorder reported to date cross-traditional diagnostic boundaries. Hum Mol Genet. 2010, [cited 2013 May 4]; Available from: http://hmg.oxfordjournals.org/content/early/2010/11/22/hmg.ddq471 Google Scholar
- Lee KW, Woon PS, Teo YY, Sim K: Genome wide association studies (GWAS) and copy number variation (CNV) studies of the major psychoses: what have we learnt?. Neurosci Biobehav Rev. 2012, 36: 556-571. 10.1016/j.neubiorev.2011.09.001.View ArticlePubMedGoogle Scholar
- Ellison-Wright I, Bullmore E: Anatomy of bipolar disorder and schizophrenia: a meta-analysis. Schizophr Res. 2010, 11: 1-12.View ArticleGoogle Scholar
- Arnone D, Cavanagh J, Gerber D, Lawrie SM, Ebmeier KP, McIntosh AM: Magnetic resonance imaging studies in bipolar disorder and schizophrenia: meta-analysis. Br J Psychiatry. 2009, 195: 194-201. 10.1192/bjp.bp.108.059717.View ArticlePubMedGoogle Scholar
- Rimol LM, Nesvåg R, Hagler DJ, Bergmann O, Fennema-Notestine C, Hartberg CB, Haukvik UK, Lange E, Pung CJ, Server A, Melle I, Andreassen OA, Agartz I, Dale AM: Cortical volume, surface area, and thickness in schizophrenia and bipolar disorder. Biol Psychiatry. 2012, 71: 552-560. 10.1016/j.biopsych.2011.11.026.View ArticlePubMedGoogle Scholar
- McIntosh AM, Job DE, Moorhead WJ, Harrison LK, Whalley HC, Johnstone EC, Lawrie SM: Genetic liability to schizophrenia or bipolar disorder and its relationship to brain structure. Am J Med Genet B Neuropsychiatr Genet. 2006, 141B: 76-83. 10.1002/ajmg.b.30254.View ArticlePubMedGoogle Scholar
- Hulshoff Pol HE, Van Baal GCM, Schnack HG, Brans RGH, Van der Schot AC, Brouwer RM, van Haren NE, Lepage C, Collins DL, Evans AC, Boomsma DI, Nolen W, Kahn RS: Overlapping and segregating structural brain abnormalities in twins with schizophrenia or bipolar disorder. Arch Gen Psychiatry. 2012, 69: 349-359. 10.1001/archgenpsychiatry.2011.1615.View ArticlePubMedGoogle Scholar
- Suppes T, Baldessarini RJ, Faedda GL, Tohen M: Risk of recurrence following discontinuation of lithium treatment in bipolar disorder. Arch Gen Psychiatry. 1991, 48: 1082-1088. 10.1001/archpsyc.1991.01810360046007.View ArticlePubMedGoogle Scholar
- Schulz SC, Thompson PA, Jacobs M, Ninan PT, Robinson D, Weiden PJ, Yadalam K, Glick ID, Odbert CL: Lithium augmentation fails to reduce symptoms in poorly responsive schizophrenic outpatients. J Clin Psychiatry. 1999, 60: 366.View ArticlePubMedGoogle Scholar
- Baldessarini RJ, Viguera AC, Tondo L: Discontinuing psychotropic agents. J Psychopharmacol. 1999, 13: 292-293. 10.1177/026988119901300314. discussion 299View ArticlePubMedGoogle Scholar
- Leucht S, Kissling W, McGrath J: Lithium for schizophrenia. Cochrane Database Syst Rev. 2007, 3: CD003834Google Scholar
- Casey DE, Daniel DG, Wassef AA, Tracy KA, Wozniak P, Sommerville KW: Effect of divalproex combined with olanzapine or risperidone in patients with an acute exacerbation of schizophrenia. Neuropsychopharmacology. 2003, 28: 182-192. 10.1038/sj.npp.1300023.View ArticlePubMedGoogle Scholar
- Tiihonen J, Hallikainen T, Ryynänen O-P, Repo-Tiihonen E, Kotilainen I, Eronen M, Toivonen P, Wahlbeck K, Putkonen A: Lamotrigine in treatment-resistant schizophrenia: a randomized placebo-controlled crossover trial. Biol Psychiatry. 2003, 54: 1241-1248. 10.1016/S0006-3223(03)00524-9.View ArticlePubMedGoogle Scholar
- Kremer I, Vass A, Gorelik I, Bar G, Blanaru M, Javitt DC, Heresco-Levy U: Placebo-controlled trial of lamotrigine added to conventional and atypical antipsychotics in schizophrenia. Biol Psychiatry. 2004, 56: 441-446. 10.1016/j.biopsych.2004.06.029.View ArticlePubMedGoogle Scholar
- Zoccali R, Muscatello MR, Bruno A, Cambria R, Micentional , Meduri M: The effect of lamotrigine augmentation of clozapine in a sample of treatment-resistant schizophrenic patients: a double-blind, placebo-controlled study. Schizophr Res. 2007, 93: 109-116. 10.1016/j.schres.2007.02.009.View ArticlePubMedGoogle Scholar
- Goff DC, Keefe R, Citrome L, Davy K, Krystal JH, Large C, Thompson TR, Volavka J, Webster EL: Lamotrigine as add-on therapy in schizophrenia: results of 2 placebo-controlled trials. J Clin Psychopharmacol. 2007, 27: 582-589. 10.1097/jcp.0b013e31815abf34.View ArticlePubMedGoogle Scholar
- Post RM: Comparative pharmacology of bipolar disorder and schizophrenia. Schizophr Res. 1999, 39: 153-158. 10.1016/S0920-9964(99)00115-2. discussion 163View ArticlePubMedGoogle Scholar
- Cardno AG, Marshall EJ, Coid B, Macdonald AM, Ribchester TR, Davies NJ, Venturi P, Jones LA, Lewis SW, Sham PC, Gottesman II, Farmer AE, McGuffin P, Reveley AM, Murray RM: Heritability estimates for psychotic disorders: the Maudsley twin psychosis series. Arch Gen Psychiatry. 1999, 56: 162-168. 10.1001/archpsyc.56.2.162.View ArticlePubMedGoogle Scholar
- Sullivan PF: The psychiatric GWAS consortium: big science comes to psychiatry. Neuron. 2010, 68: 182-186. 10.1016/j.neuron.2010.10.003.View ArticlePubMedPubMed CentralGoogle Scholar
- Green EK, Grozeva D, Jones I, Jones L, Kirov G, Caesar S, Gordon-Smith K, Fraser C, Forty L, Russell E, Hamshere ML, Moskvina V, Nikolov I, Farmer A, McGuffin P, Holmans PA, Owen MJ, O'Donovan MC, Craddock N, Wellcome Trust Case Control Consortium: The bipolar disorder risk allele at CACNA1C also confers risk of recurrent major depression and of schizophrenia. Mol Psychiatry. 2009, 15: 1016-1022.View ArticlePubMedPubMed CentralGoogle Scholar
- McDonald C, Bullmore E, Sham P, Chitnis X, Suckling J, MacCabe J, Walshe M, Murray RM: Regional volume deviations of brain structure in schizophrenia and psychotic bipolar disorder: computational morphometry study. Br J Psychiatry. 2005, 186: 369-377. 10.1192/bjp.186.5.369.View ArticlePubMedGoogle Scholar
- McDonald C, Marshall N, Sham PC, Bullmore ET, Schulze K, Chapple B, Bramon E, Filbey F, Quraishi S, Walshe M, Murray RM: Regional brain morphometry in patients with schizophrenia or bipolar disorder and their unaffected relatives. Am J Psychiatry. 2006, 163: 478-487. 10.1176/appi.ajp.163.3.478.View ArticlePubMedGoogle Scholar
- McDonald C, Bullmore ET, Sham PC, Chitnis X, Wickham H, Bramon E, Murray RM: Association of genetic risks for schizophrenia and bipolar disorder with specific and generic brain structural endophenotypes. Arch Gen Psychiatry. 2004, 61: 974-984. 10.1001/archpsyc.61.10.974.View ArticlePubMedGoogle Scholar
- Stahl SM: Stahl’s Essential Psychopharmacology: Neuroscientific Basis and Practical Applications. 2008, Cambridge, UK: Cambridge University PressGoogle Scholar
- Goodwin FK: Rationale for long-term treatment of bipolar disorder and evidence for long-term lithium treatment. J Clin Psychiatry. 2002, 63: 5-12.PubMedGoogle Scholar
- Schwarz C, Volz A, Li C, Leucht S: Valproate for schizophrenia. Cochrane Database Syst Rev. 2008, 3: CD004028Google Scholar
- Amann B, Born C, Crespo JM, Pomarol-Clotet E, McKenna P: Lamotrigine: when and where does it act in affective disorders? A systematic review. J Psychopharmacol. 2011, 25: 1289-1294. 10.1177/0269881110376695.View ArticlePubMedGoogle Scholar
- Goodwin FK, Jamison KR: Manic-Depressive Illness: Bipolar Disorders and Recurrent Depression. 2007, New York: Oxford University Press, 2Google Scholar
- The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1741-7015/11/127/prepub
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