you should have his testosterone level checked. his anger may be due to this being off which can occur from a concussion. Negative thoughts is also a symptom of low testosterone. I have seen that one before at low levels. make sure you get the results so you can compare to acceptable ranges for the age group of your son. regular doctors are truly clueless about hormones. if your son is 8-25 he should be at the top end of the range. if hes low he could manifest other low testosterone symptoms like depression, fatigue brain fog, low libido etc (google low testosterone)