Addiction Triptych 1.3: Withdrawal

Fully ensnared by dependence, our protagonist develops tolerance to the compound in question due to downregulation of endogenous neurotransmitter production.

Dopamine downregulation for example results because the brain notes the excessive dopamine levels released by an addictive chemical agent and tries to compensate by producing less dopamine total in an effort to bring the system back to its normal equilibrium. When the chemical stimulus is removed the brain is still making significantly less dopamine, and now - absent the surfeit of the neurotransmitter released by the chemical - there are inadequate levels of dopamine for normal function.

Withdrawal symptoms are thus a consequence of uncompensated for downregulation in the sudden absence of a chemical that artificially increases tissue levels.