View Full Version : Heritability of ADHD among Swedes

31-08-16, 15:37

"The birth year adjusted HRs were as follows: 70.45 for monozygotic twins; 8.44 for dizygotic twins; 8.27 for full siblings; 2.86 for maternal half-siblings; 2.31 for paternal half-siblings; 2.24 for full cousins; 1.47 for half cousins. Maternal half-siblings had significantly higher HR than in paternal half-siblings. The HR did not seem to be affected by index person's sex. Full siblings of index persons with ADHD diagnosis present at age 18 or older had a higher rate of ADHD (HR: 11.49) than full siblings of index persons with ADHD diagnosis only before age 18 (HR: 4.68).Conclusions

Familial aggregation of ADHD increases with increasing genetic relatedness. The familial aggregation is driven by not only genetic factors but also a small amount of shared environmental factors. Persistence of ADHD into adulthood indexes stronger familial aggregation of ADHD."

01-09-16, 13:52
Some traits like height and intelligence are inherited more strongly from one's father, while others tend to be passed on more by mothers. This is called sex-biased gene expression. Incidentally, this is why the offspring of a male lion with a female tiger (i.e. a liger (https://en.wikipedia.org/wiki/Liger)) looks quite different from that of a a male tiger with a female lion (i.e. a tigon (https://en.wikipedia.org/wiki/Tigon)).

Apparently the genes relating to ADHD (attention, emotional stability) in humans may be slightly more active when inherited from the mother. From my observations, emotions and some basic character traits relating directly to emotional reactions tend to be more strongly inherited from the mother.