This study will be conducted as a randomized, double blind, placebo-controlled superiority trial. Three parallel treatment groups will be examined with a 1:1:1 allocation: 1) sublingual placebo, 2) sublingual Melatonin 3mg, and 3) sublingual Melatonin 10mg. Groups will be allocated using a randomization sequence that will be created in variable random block sizes (multiples of 3: 3, 6, and 9) to aid in concealment of next allocation, using random number generating software. The primary endpoint is the change on the Post-Concussion Symptom Inventory Score for parent and adolescent. The design allows for dose dependent response assessment.