The influence of genes and environment on the development of bipolar disorder: A twin study

Bipolar disorder (or manic-depressive disorder) is a severe mood disorder in which episodes of (hypo) mania (e.g. elevated mood en hyperactivity) and depression (e.g. decreased mood and reduced activity) alternate with periods of normal mood and functioning. Genetic factors as well as environmental factors play a role in the development of bipolar disorder. A serious problem for bipolar disorder is a delay of several years between the first mood episode(s) and the diagnosis. Afterwards it can take several years before starting the right treatment. This twin study shows that the genetic vulnerability for bipolar disorder can appear in several ways and in several phases of life.
•Early during intrauterine life between the 10th and the 17th weeks of gestation an abnormal development of the embryonal ectoderm tissue can lead to changes in palmar dermatoglyphics, which are associated to structural brain abnormalities in adult life.
•MRI scans of the brain of the adult bipolar twins show white matter abnormalities
•In early adolescence (temporary) under performance in school can be a marker of the genetic vulnerability to develop bipolar disorder.
•There is genetic overlap between the development of bipolar disorder and an auto-immune disease of the thyroid. This auto-immune thyroiditis can be seen as an endophenotype of bipolar disorder.

Endophenotypes can be useful to identify people with a higher risk for developing bipolar disorder, to diagnose them earlier and to start the treatment more soon (and probably even preventive).