Original sentence: Studies show that there is a familial transmission of the disorder which does not occur through adoptive relationships, however adoption-based studies are not reliable in this context.Twin studies indicate that the disorder is highly heritable and that genetics contribute about three quarters of the total ADHD population, though such studies are known to be heavily flawed
Edited sentence: Studies show that there is a familial transmission of the disorder which does not occur through adoptive relationships.Twin studies indicate that the disorder is highly heritable and that genetics contribute for about three quarters of the total ADHD population