Overstimulation of D2 receptors in the brain will lead to decreased levels of dopamine and upregulation of dopamine receptors. the body is in homeostasis. If you use cocaine long time the body adapts. When you indulge in cocaine, there is no way back so to speak. Now if you cant buy crack anymore, there are all these dopamine receptors waiting for their dopamine. It never comes. Now you start too worry. Maybe it is my fault. What willl other people say? I have to leave this place! Now this process can be multiplied through taking chemicals or through genetically moderated levels of naturally occuring neurotransmitters.

The framework of the aberrant salience and the mesolimbic salience system, and dopaminergic trasmission have a role in the delusionals symptoms. It can be useful to add that not only dopaminergic drugs like cocaine play a role, but also cannabinoid like drugs ( that have receptors on their own ) can cause some typical psychotic symptom.