There have been many studies done on dopamine's effect on the brain. While these studies have not ended in absolutely conclusive results, the findings have been illuminating as to dopamine's role in addiction. Dopamine is a neurotransmitter in the brain affecting numerous functions, but the two most significant roles it plays in addiction are pleasure and impulsiveness. Pleasure and impulsiveness are particularly relevant to an individual's mental health.

When the brain is functioning well, it signals a positive reward in the form of pleasure from dopamine in such activities as eating, drinking or having sex. This is all well, good and healthy. Everyone enjoys these dopamine-induced bursts of pleasurable sensations. Many will go out of their way to keep the happiness going. Since dopamine also influences impulse control, it is not difficult to imagine that when these two get together in the brain, addiction can be the inevitable result.

Dopamine and Pleasure

Alcohol and drugs like cocaine, stimulants and heroin increase the output of dopamine in some way. Not only do these substances increase dopamine output, they also alter the way dopamine functions in the body. Some drugs change the flow of neurotransmitters, others bypass them and act directly on receptors in the brain altering the signals these receptors produce. Such changes occur in people who abuse drugs to the point of addiction. Short-term use of these same drugs simply produce the same pleasurable reward and afterwards things get back to normal for most people.

However, for addicts, the long-term effects alter the brain in a more permanent manner. The drugs and alcohol that once stimulated the production of dopamine are now a necessity to produce pleasure and elation because the brain has ceased to do it on its own.

As the brain becomes accustomed to receiving drugs, it is possible that the dopamine output decreases. Also, this change in brain function has an impact on the ability to process other pleasurable experiences. Food, sex and favorite activities or being with loved ones lose their pleasurable sensations. A decrease in the release of dopamine can numb a person to life's everyday rewards.

Dopamine and Impulse Control

Scientific studies found that lower dopamine activity in the mid-brain also leads to increased impulsivity. This can lead the addict to further substance abuse and more risky behaviors.

The research also found that the tendency to substance abuse behavior lies in an individual's innate tendency toward impulsiveness, which is linked to faulty regulation of dopamine in the mid-brain.

At the core of the study model conducted by Joshua Buckholtz, Ph.D. Department of Psychology at Harvard University, is an understanding of how the brain signals for dopamine to be released. The dopamine-containing neurons are in the mid-brain area. Some of these cells release dopamine into the striatum, a mid-brain region known to be involved in motivation and reward.

So when an individual experiences something rewarding or even sees something that is learned to produce a reward, these mid-brain dopamine neurons activate. They then release more dopamine triggering activity in the reward center of the brain.

To keep the cells from inundating the area with an overload of dopamine, special regulatory sensors called D2 auto receptors shut the flow down when they sense the proper level of dopamine has been reached. Think of it as similar to the way a thermostat works in home heating. Ergo, impulsive people have a broken dopamine thermostat.

Dopamine has long been implicated in impulsivity, but the exact mechanisms involved remain somewhat murky. The ability to deliberate on the consequences of one's actions is crucial to human behavior. However, human beings differ widely in their ability for such deliberation, and a sizeable percentage of the population persistently makes rash, spontaneous and, very often, destructive decisions. Such differences strongly predict liability for a range of behavioral disorders including Attention Deficit Hyperactive Disorder (ADHD), antisocial personality disorder and substance abuse.

Clearly more research needs to be done on the effects of dopamine on the human brain. While much good has come from those already underway, dopamine deserves more in-depth research to study its effects not only on addiction, but other behavior disorders and diseases such as Parkinson's.

Sources:

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4108583

[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3161413

[3] https://link.springer.com/article/10.1007/s00213-006-0578-x

[4] https://www.inspiremalibu.com/blog/drug-addiction/dopamine-and-addiction