Würtz Schmidt spent a long spell in the hot seat of provisional race leader after clocking 37 minutes and 10 seconds over the undulating 30-kilometre course as one of the early group of starters.
It was a time that all of the subsequent riders could not get anywhere near and the 21-year-old swapped the hot seat for the top step of the podium to receive his rainbow jersey. It is the second of Würtz Schmidt's career, having won the junior TT title in 2011.
German pair Maximilian Schachmann and Lennard Kamna secured silver and bronze - the latter's performance was particularly noteworthy as he was the last rider off and had to endure a late rainstorm and rising winds.
Welshman Doull finished in fifth, 36 seconds adrift of Würtz Schmidt, with fellow British rider Scott Davies in 34th place at 2-19. Irish hope Ryan Mullen - silver medallist last year and one of the pre-race favourites - finished in 11th place.
Earlier in the day, Chloe Dygert (USA) gave the home nation a perfect start to the 2015 Worlds with a win in the opening individual event of the championship: the junior women's individual time trial.
Dygert clocked 20 minutes and 18 seconds around a 15 kilometre course to take the title, with American compatriot Emma White claiming silver. Australian Anne-Leeza Hull completed the podium with bronze.
British riders Abby-Mae Parkinson and Elizabeth Holden finished in 23rd and 31st places respectively.
Under-23 men individual time trial, 30km
1. Mads Würtz Schmidt (Denmark) in 37-10.96
2. Maximilian Schachmann (Germany) at 12 secs
3. Lennard Kamna (Germany) at 21 secs
4. Truls Engen Korsaeth (Norway) at 36 secs
5. Owain Doull (Great Britain) at 36 secs
6. James Oram (New Zealand) at 37 secs
7. Miles Scotson (Australia) at 40 secs
8. Thery Schir (Switzerland) at 41 secs
9. Marlen Zmorka (Ukraine) at 42 secs
10. Daniel Eaton (USA) at 43 secs
11. Ryan Mullen (Ireland) at 49 secs
34. Scott Davies (Great Britain) at 2-19
38. Eddie Dunbar (Ireland) at 2-34
Junior women individual time trial, 15km
1. Chloe Dygert (USA) in 20-18.47
2. Emma White (USA) at 1-05
3. Anne-Leeza Hull (Australia) at 1-26
4. Pernille Mathiesen (Denmark) at 1-30
5. Juliette Labous (France) at 1-35
6. Aafke Soet (Netherlands) at 1-40
7. Daria Pikulik (Poland) at 1-41
8. Gillian Ellsay (Canada) at 1-45
9. Agnieszka Skalniak (Poland) at 1-47
10. Emeliah Harvie (Canada) at 1-49
23. Abby-Mae Parkinson (Great Britain) at 2-22
31. Elizabeth Holden (Great Britain) at 3-06
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