[McGavin999]

Being mentally strong would have nothing to do with a physical reaction to the drug. The fact that he had brainstem problems makes it highly likely that the drug was responsible for his actions.

Actually, it makes far more sense that it was the drug than that a Spec Ops guy would suffer from cowardice.

[somemoreequalthanothers]

Being mentally strong would have everything to do with overcoming a physical reaction. That is what advanced training teaches, overcoming cold, heat, pain, fear, etc. with the mind. A drug should not immediately render all that useless.