Stage 1: experimentation.
It's the initial phase of substance usage. In general, it ignited by curiosity or the effort to run from current situation
Stage 2: Regular use
In this phase, users' body will start to crave the existence of the substance in their body
Stage 3: Substance abuse/Risky behavior
The substance that exist in users' system started to affect brain processing which affect users' tendency in comitting risky behavior
Stage 4: Addiction or chemical dependency
At this point, users' body will start to display some sort of pain if it sense if it stop injecting the substance regularly.