Participants
head injury
The original study had five subjects who were included on two different occasions. For these subjects the first inclusion date and randomization allocation was used. Of the original 911 subjects, 1.4% (N = 13) had an incomplete PIN and could not be followed up at Statistics Sweden, 3.6% (N = 33) were too young to have graduated (under 16 year olds without compulsory school leaving grades), 2.0% (N = 18, exclusion criteria) had graduated before their head injury, and 1.6% (N = 15) were lost to follow up (