While tobacco addiction exhibits a similar biological mechanism among smokers, Duke University researchers have found for the first time that those mechanisms can vary among individuals according to the reasons they ascribe to their craving.
The research, published online in March in the journal Neuropharmacology and funded by Phillip Morris USA, could help with tailoring better smoking cessation treatments, according to investigators.
In the study, 15 smokers (averaging 22 cigarettes per day) were deprived of nicotine at varying levels for two weeks. Researchers using FDG-PET found increased activity associated with addictive craving in the thalamus, striatum, and anterior cingular cortex, validating previous findings.
The researchers then examined written questionnaires for reasons subjects said they wanted cigarettes such as to reduce hunger or alleviate stress. They found a striking correlation between these specific reasons and isolated FDG activity in these three brain regions.
Led by Jed E. Rose, Ph.D., the researchers from the departments of psychiatry and radiology found that changes in the thalamus were most dramatic among those who said they smoked to calm down when under stress. The thalamus plays an important role in sensory gating. The increase in thalamic activity accompanying deprivation may reflect a deficit in sensory gating and possibly would result in a reduced ability to cope with stressful stimuli, especially in the most highly dependent smokers for whom calming effects were important, according to the study.
Changes in the striatum were most notable in people who smoked to satisfy craving and for pleasurable relaxation. The anterior cingulate cortex, a region vital to self-control and concentration, was noticeably activated in people who smoked to manage their weight.
Smokers trying to quit are hit with multiple psychological challenges rooted in biological processes. They may suffer from impaired self-regulation due to changes in anterior cingulate functioning, excessive sensitivity to craving via dysregulated striatal dopamine reward pathways, altered emotional responses from disruptions in amygdala activity, and an inability to cope with stress due to a deficit in the thalamic filtering system.
"This multiplicity of deficits might account for the difficulty smokers report with continual thoughts of smoking that they cannot rid themselves of...," the study said.
Researchers concluded that the findings show important differences among smokers in brain responses that underlie the smoking habit. Such brain scans may yield diagnostic tests for predicting which smokers will benefit most from particular quitting methods.
Their next step for researchers is to use PET to scan smokers undergoing nicotine replacement therapy and examine the brain activity associated with it.
For more information from the Diagnostic Imaging archives:
PET proves one puff isn't enough
PET lights up brain circuitries of tobacco dependence
Brain damage from alcohol worsens with tobacco use
CT exams help smokers kick the habit