Addiction as a Brain Disease

Addiction is a disorder that involves complex interactions between genes, development and the social environment.  Studies employing neuroimaging technology paired with behavioral measurements have led to extraordinary progress in elucidating many of the neurochemical and functional changes that occur in the brains of addicted subjects.  Although large and rapid increases in dopamine have been linked with the rewarding properties of drugs, the addicted state, in striking contrast, is marked by significant decreases in brain dopamine function.  Such decreases are associated with dysfunction of prefrontal regions (ie orbitofrontal cortex, cingulate gyrus and dorsolateral prefrontal cortex) that are necessary for self-control, which could explain the impulsive and the high risk behaviors observed in drug users.  In addiction, disturbances in salience attribution result in an enhanced incentive value given to drugs and drug-related stimuli at the expense of decreased sensitivity for non-drug reinforcers.  Dysfunction in inhibitory control systems, by decreasing the addict’s ability to refrain from seeking and consuming drugs, ultimately results in the compulsive drug intake that characterizes the disease. Discovery of such disruptions in the fine balance that normally exists between brain circuits underling reward, motivation, memory and self-control have important implications for designing multi-pronged therapies for treating addictive disorders. Successfully treating addiction is paramount to effective HIV/AIDS prevention. Since the inception of the HIV epidemic, drugs of abuse have had a large impact on its expansion. Though injection drug use is the most commonly recognized vector for transmission of HIV by drugs, the intoxicating effects of drugs on the brain by interfering with self-control mechanisms also promote risk-taking behaviors that increase the likelihood of HIV infection.  Drug abuse also impacts the trajectory of the infection; some drugs through their deleterious effects to the immune system (ie. opiates, alcohol) or through their interactions with HAART (ie alcohol) but also by affecting compliance with HIV treatment regimes can result in worse clinical outcomes.   While interventions such as needle exchange programs (NEP), community outreach, and drug abuse treatment have been found to be effective HIV prevention strategies for drug users, proactive seeking of drug abusers for testing their HIV status; and for those that are HIV positive their engagement both in HAART and substance abuse treatments has been shown to be effective in improving patient outcomes and also in preventing HIV transmission in the larger community.