Biological Models of Addiction

Biological models of addiction explain addictive behaviour in terms of brain chemistry, neural pathways, and genetic predisposition. These models are essential for understanding why addiction is so difficult to overcome and why pharmacological treatments can be effective. The AQA specification focuses on the role of the brain's reward system, the effects of specific substances on dopamine pathways, genetic vulnerability, and the processes of tolerance and withdrawal.

Key Definition: The mesolimbic dopamine pathway is the brain's reward circuit, running from the ventral tegmental area (VTA) through the nucleus accumbens to the prefrontal cortex. It is activated by pleasurable experiences and is hijacked by addictive substances and behaviours.

---

The Brain's Reward System

All pleasurable experiences — eating, social interaction, sex — activate the mesolimbic dopamine pathway:

1. The ventral tegmental area (VTA) in the midbrain produces dopamine
2. Dopamine is released into the nucleus accumbens (the brain's "pleasure centre")
3. The prefrontal cortex evaluates the experience and forms memories and associations

This system evolved to reinforce survival behaviours — activities that promote survival and reproduction are experienced as pleasurable, making them more likely to be repeated.

How Drugs Hijack the Reward System