A 2015 book, “Hijacked Brains: Experience and Science of Chronic Addiction,” by Harvard Medical School physician Henrietta Robin Barnes, makes a strong case against the stigmatization, blame and discrimination society directs toward addicts, and argues that those attitudes fly in the face of 50 years of addiction science.

Drawing on her 30 years of experience working with patients with chronic addictions, Barnes concludes that " … established addiction is neither a pleasure nor a choice. Any illness that deprives a person of his ability to perceive reality, to make reasonable decisions, to feel in control of his own life, and to have hope for the future is a heavy burden indeed."

Backing up those claims with the latest in neurology, she explains that disruptions in the regulation of brain networks involved in the experience of reward cause behaviors associated with addiction.

In a healthy brain, behaviors that repeatedly bring about feelings of reward are self-reinforcing. Positive reinforcement leads to memory and learning, and eventually the series of behaviors that lead to the reward become habituated, freeing up the cognitive areas of the brain for more important work.

Environmental cues can activate the expectation for a reward, which in turn sets in motion the automatic behaviors to obtain it. In this process, areas in the cognitive part of the brain called the prefrontal cortex compare benefits and risks of the reward. The prefrontal cortex can cut short the process if it finds it is outweighed by other priorities.

Barnes quotes Dr. Stephen Hyman who says, "Mechanisms that evolved to motivate survival behaviors, the pursuit of natural rewards, are usurped by the potent and abnormal dopamine signal produced by addictive drugs."

It is widely understood that the neurotransmitter dopamine plays a role in addiction. However, Barnes argues it may not be as simple as causing addicts to feel pleasure when using the drug and lack of pleasure for other activities.

She describes a new model, supported by studies, which places dopamine as a key player in the process of expectation, learning, memory formation and relearning. Its levels in the brain are affected by comparison of an outcome with an expectation: more dopamine is released for a greater-than-expected reward experience (leading to some stress hormones making you more alert and ready to learn), lower levels for worse-than-expected outcomes, and no change in levels for rewards that match the expectation. Learning occurs, regarding behavior related the reward, when there is a difference between the expectation and the outcome.

Every addictive drug studied, Barnes said, has been found to increase dopamine levels in the brain, causing every experience with the drug to be perceived as better than expected. This teaches the user to increase the behavior that led to it. Through conditioning, the behavior becomes automatic.

The prefrontal cortex then becomes less involved in the actions, as do its processes of self control, behavior monitoring, emotional regulation, motivation, attention, insight, learning, memory, decision-making and attribution of importance.

The orbitofrontal cortex also reacts to the waves of dopamine by reducing its number of dopamine receptors which blunts responses to natural pleasures, disrupts its ability to prioritize different rewards, and makes the drug's reward with its high dopamine levels the most important of all to the individual.

At this point, "the only salient motivator is the drug itself or its environmental cue," which, as in a healthy brain, can trigger habitual behavior, Barnes says.

At the same time, the cognitive brain has less regulatory control over the behavior. Based on brain imaging studies, she says, "the neural processes that conduct sensory impulses to the neurons in performing behaviors do not appear to be subject to the dictates of conscious will or willpower."

Other theories suggest a negative reward cycle is also in play, causing negative feelings to trigger the drug-seeking behavior. If these findings are true, Barnes argues, it would be more productive as a society to offer better treatment for addiction rather than discrimination, judgment and punishment.