Addiction and Brain Changes

Attached a link Abnormal Brain Structure Implicated in Stimulant Drug Addiction to an interesting article published in a recent edition of Science. The authors report that they discovered abnormalities in fronto-striatal brain systems implicated in self-control in both stimulant-dependent individuals and their biological siblings who have no history of chronic drug abuse; these findings support the idea of an underlying neurocognitive endophenotype for stimulant drug addiction.
Drug dependence is increasingly recognized as a “relapsing brain disorder”and, in support of this view, marked structural changes in striatal and prefrontal brain regions have been reported in people dependent on stimulant drugs . These reports, however, raise the question of whether these brain abnormalities may have predated drug-taking, rendering individuals vulnerable for the development of dependence.
Individuals at risk for drug dependence typically have deficits in self-control, which may reflect a diminished ability to recruit prefrontal networks for regulating behavior. Stimulant drugs are highly reinforcing, because they directly affect brain systems implicated in motivated behavior, such as the basal ganglia and the limbic system, and they modulate control systems in the prefrontal cortex. Malfunction of these circuitries may increase the susceptibility for stimulant-induced neuroadaptive changes and facilitate the development of drug dependence.
In the study they compared brain structure and the ability to regulate behavior in 50 biological sibling pairs; within each pair, one sibling satisfied the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria for dependence on stimulant drugs and the other had no history of chronic drug or alcohol abuse. The sib-pairs were also compared with 50 unrelated healthy volunteers matched for age and intelligence quotient.
The findings indicate that gray matter changes in the dorsal striatum, together with abnormal inferior prefrontal cortical connectivity, underlie an increased risk for developing stimulant drug dependence. However, the almost equivalent impairments in SSRT (Stop-Signal Reaction Time) in both the stimulant-dependent individuals and their unaffected siblings need careful interpretation, as they do not reflect the classic pattern for endophenotypes, i.e., that the first-degree relatives have trait values intermediate between the patients and the unrelated healthy volunteers. Presumably, the siblings must have some other resilience factors that counteract the familial vulnerability to drug dependence. The identification of these brain and behavioral biomarkers for familial risk of drug dependence demonstrates that an individual’s predisposition to become addicted to stimulant drugs may be mediated by brain abnormalities linked to impaired self-control.