03 août 2008

Algunas personas enfocan su vida de modo que vivan con entremeses y guarniciones. El plato principal nunca lo conocen.

Francisco de Goya y Lucientes, El tres de Mayo de 1808, 1814.

Bipolar and unipolar conditions genetically overlap

After the original studies by Leonhard and by Perris reported that familial diVerences between recurrent depressive illness and manic-depressive illness, subsequent family and genetic studies commonly reported an overlap between the two forms of mood disorder, supporting a unitary construct. Both forms of illness occur with increased frequency in the families of patients with manic-depressive illness. When recurrent depressive illness is defined as melancholia, families have an increased risk for manic depression.

Twin studies show this overlap. In an analysis of 30 monozygotic and 37 dizygotic twin pairs, the proband concordance was higher for monozygotic than for dizygotic twins, with heritability estimated at 89%.66 In almost 29% of the monozygotic pairs, one twin had both manic and depressive episodes while the other had recurrent depressive illness. Among the dizygotic pairs 13.5% had a mixed concordance. The investigators tested several liability models and concluded that manic-depressive illness was not simply a more severe form of recurrent depressive illness, but that nevertheless, there was substantial genetic overlap between the twoforms (about 30%) that may represent the risk for depressive illness.