CONSANGUINITY AS A RISK FACTOR FOR SEVERE MENTAL DISORDER: HISTORICAL STUDY OF HALF-SIBLINGS
The role of consanguinity as a risk factor for serious mental illness continues to be a subject of debate today. There are 2 basic techniques to study this problem: the so-called Runs of Homozygosity (ROH), and the study of genealogical trees. The first one has been applied to large samples of population and has not confirmed this relationship. The study of genealogical trees has obtained inconclusive results, perhaps due to the fact that, in general, studies have been limited to a maximum of 6 generations. This problem could be overcome by studying the ancestors of the royal families, in which there is no such limitation.
This work studies the coefficient of inbreeding in 8 pairs of siblings with only one common parent (half-brothers) belonging to European royal families, in which one of them might have been affected by a mental illness.
To determine if the coefficient of inbreeding is higher in the sick sibling than in the healthy one.
A historical study was conducted about possible mental illnesses in European royal families, with special attention to cases involving half-brothers. Genealogical trees were created using the PED-PRO program, with a database of 25,178 individuals, calculating the coefficient of inbreeding (F) for 24 generations.
FI Sick sibling FI Healthy sibling
Joanna of Castile, “the Mad” / Alonso de Aragón 3.3304 0
Fernando VI of Spain / Charles III of Spain 9.5022 3,8264
Peter of Castile / Henry II of Castile 15.6372 0.9737
Charles V, Holy Roman Emperor / Catherine of Austria, Queen of Portugal 20.242 0.8949
Mariana of Austria / Eleanor of Austria, Queen of Poland 15.2609 3.2473
John V of Portugal / Isabel Luísa, Princess of Beira 0.2566 0.0844
Rudolph, Prince of Anhalt-Zerbst / Elisabeth of Anhalt-Zerbst 2.8214 1.6876
Henry VI of England / Edmund Tudor, 1st Earl of Richmond 1.1314 0.0803
- The coefficient of inbreeding is greater in the sick half-brother than in the healthy one.
- The study of large genealogical trees of royal families provides greater detail in the determination of the coefficient of inbreeding and its risks.
- According to these results, consanguinity is a risk factor for serious mental illness.