Bipolar disorder, previously known as manic depression, is a mental disorder characterized by periods of depression and periods of abnormally elevated mood that last from days to weeks each. Bipolar twin studies show that one twin can have the condition while the other does not. Research suggests there is a strong genetic component in bipolar disorder. Family, twin, and adoption studies have been essential in defining the genetic epidemiology of bipolar disorder over the past several decades. Twin studies have established that bipolar disorder is among the most heritable of medical disorders and efforts to identify specific susceptibility genes have intensified over the past two decades. Mol Psychiatry. Family History: Bipolar disorder tends to run in families. It is a disorder that has been thought for some time to have a heritable component. Family, twin, and adoption studies have been essential in defining the genetic epidemiology of bipolar disorder over the past several decades. 15 However, most adoption studies produce lower heritability estimates than found in twin analyses for the same phenotype. The likelihood of an identical twin developing bipolar disorder if their twin has the condition is between 40–70%. A review of the evidence from family, twin and adoption studies for a genetic contribution to adult psychiatric disorders. 7(4):405-11. . Badner JA, Gershon ES. At the same time, the investigation of the causes of the disease is continuing, because it will allow developing effective methods of prevention and treatment. Family studies had to include a comparison group. Bipolar disorder (BPD) is associated with altered regional brain function during the performance of cognitive tasks. Our estimate of the heritability of bipolar disorder (0.44) is lower than estimates from prior twin samples 13,14 and the estimate from a large, Swedish twin-sibling study: 0.59.  Because identical twins share 100% of their DNA, the fact that the numbers vary so greatly suggests that environmental factors also play a role and that carrying genes associated with bipolar disorder does not necessarily mean someone will develop this condition. Bipolar Disorder 1 Genetics of bipolar disorder Nick Craddock, Pamela Sklar Studies of families and twins show the importance of genetic factors aff ecting susceptibility to bipolar disorder and suggest substantial genetic and phenotypic complexity. Up to 50% of untreated patients attempt suicide at least once, a NAMI study reveals. Epigenetics refers to changes in genes that do not affect the inherited sequence of DNA, but affect how easily the DNA is transcribed to produce proteins. Twin studies have found that when one identical twin has the condition, the likelihood that their twin sibling will also have it is around 40%. Bipolar disease features states of severe depression that usually fluctuate with at least one episode of intense elation or mania. Studies of families and twins show the importance of genetic factors affecting susceptibility to bipolar disorder and suggest substantial genetic and phenotypic complexity. The relative contribution of genetic and environmental risk factors for BPD to these changes has not yet been quantified. 2004 Nov. 16(4):260-83. . Twin studies have the advantage of taking into account both genetic and environmental factors, and may be more likely to outline the genetic basis of cognitive deficits in HR. To date, there are no published twin studies in pediatric offspring of parents with BD, or even on pediatric BD. Psychological Medicine, Vol. Twin studies for the investigation of the relationships between genetic factors and brain abnormalities in bipolar disorder - Volume 25 Issue 6 - L. Squarcina, C. Fagnani, M. Bellani, C. A. Altamura, P. Brambilla Background Twin studies of bipolar affective disorder (BPD) have either been small or have not used explicit diagnostic criteria. The nosological status of schizoaffective disorders remains controversial. Bipolar disorder, previously known as manic depression, is a mental disorder characterized by periods of depression and periods of abnormally elevated mood that last from days to "Because of twins studies, we now know that genes account for the same amount of variability in eating disorders as they do in schizophrenia and bipolar disorder. If the elevated mood is severe or associated with psychosis, it is called mania; if it is less severe, it is called hypomania. 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