Positron emission tomography (PET) imaging of brain functioning indicates that dopamine is associated with substance use (126, 127). However, measuring brain dopamine markers involves radioligands, limiting their use. Functional MRI (fMRI) produces structural and functional data, but few fMRI or PET studies have differentiated brain functioning predating and consequent to onset of substance use disorders (128). Furthermore, brain imaging findings based on group differences are not specific enough to use as diagnostic markers in individual cases. Finally, abnormalities in brain regions and functioning that are associated with substance use disorders overlap with other psychiatric disorders. In sum, biomarkers are not yet appropriate as diagnostic tests for substance use disorders. Continued research in this area is important.
