Even if "drugs" are listed as the cause of death on a death certificate, it's often a second order effect.

My friend was a veteran. He served in both the Marine Corps and the Army. He was shipped to Afganistan and Iraq.

He drank heavily and smoked a little weed every now and then, but this was a second order effect.

The bombs didn't kill him.

The bullets didn't kill him.

The booze may have been the kill shot, but he died for his government.