Addiction affects another area of the brain called the hypothalamus. The hypothalamus has many duties. It controls body temperature, hunger, thirst, and sleep. The hypothalamus plays a key role in our response to stress. Stress regulation is highly relevant to our understanding of addiction. When an individual experiences stress, the hypothalamus releases chemicals called hormones. These hormones allow the brain and the body to respond to that stress. Unlike neurotransmitters (which are chemicals limited to the brain) hormones travel throughout the body via the blood system. Therefore, hormones can exert an effect on other body systems as well. When these chemical hormones operate in the brain, we refer to them as neuromodulators. These hormones (neuromodulators) can act just like neurotransmitters in the brain. Like neurotransmitters, they have their own receptors associated with them.
Stress is a well-known relapse trigger. It can prompt powerful cravings in addicted persons. Many of us know someone who tried to quit smoking but ultimately relapsed when they became "stressed out." Unfortunately, during the initial period of recovery withdrawal symptoms create stress. This creates an unfortunate cycle. Stress prompts addictive use, while efforts to discontinue use prompt stress. During withdrawal, these stress hormones are elevated. Even though stress levels are high, the brain's anti-stress neuromodulators appear to decrease, as do dopamine and serotonin in the nucleus accumbens. This suggests that withdrawal affected the reward system (evidenced by decreasing dopamine and serotonin). At the same time, withdrawal activates the stress and anxiety systems. This "1-2 punch" heightens the negative experience of withdrawal. This prompts people to seek relief via the addictive substance or activity (i.e., relapse).
In summary, the neurotransmitter pathways associated with the amygdala and the hypothalamus play a crucial role in sustaining the addiction process. This occurs thorough:
1. The negative emotional memory that is associated with drug withdrawal.
2. The positive emotional memory that is associated with drug cues.
3. The disruption that occurs to stress regulation.
4. The pleasurable relief from withdrawal symptoms that occurs by resuming drug use or addictive activities.