There was a kid on my HS team with pretty bad asthma and ADD.
Funny thing was, on training runs, if you kept a conversation with the guy, he could run 5 miles in about 37 minutes until the asthma really got to him.
In races, with no one to talk to, he would usually run 30+ minutes for 5k.
His explanation at the end was just that he couldn't keep his mind on the race.
Many times he also lost the course, despite a long stream of people to follow.
Finished DFL in the league every year in XC. Similar results in track. Funny thing was, towards the end of his senior year, he gets thrown in the 400 hurdles and runs a very respectable time.
Went on to achieve some minor success in college.