Drug Abuse?

Surfing the Milblogs, I ran across this long post...most of it I have no expertise, but as a doctor, I found this line interesting:

Fun fact: Random autopsies on dead insurgents shows a high level of opiate use.

Why opiates and not marijuana
Well, Iran has a high rate of opiate addiction...but Iran is Shiite, and the source of most of the very bad bombs in the south...whereas most of the foreign "insurgents" (read outsiders) are from Sunni areas, such as Syria or Saudi Arabia...

Now, there is a lot of under the cover drinking and drug use in Saudi arabia but are they getting their opiates there? Or from Iran? Or are the drug dealers, like the dealers in other areas of the world, apolitical, and sell to all comers?
Inquiring minds want to know...