How are opiates addictive? what effects do they have on the body and brain?

Hard to answer: Opiates bind to "receptors" in teh brain and nervous system which gives them their analgesic and euphoric effects. People to become addicted to the euphoria. When taken for long periods for chronic pain, a dependency may develop which may not be related to the euphoria effects. Hard to explain in detail. Speak to your physican.

Complicated: Opiates change mood and neurotransmitters in the brain. They can cause euphoria, sleepinesses, spaciness, addiction is very complicated and can occurr for many different reasons. Usually does not occurr if opiates are taken as prescribed.