According to the US National Library of Medicine and National Institutes of Health, prolonged use of opiates creates long-lasting changes in the brain that will most likely lead to drug addiction. Many factors, primarily neurobiological, take effect on the brain’s natural reward system, creating a dependency, known as addiction.
The same way a key fits a lock, particular neurotransmitters activate specific receptor molecules. When opiates like heroin, Vicodin, and Oxycontin enter the blood stream, the brain reacts in a way that hijacks the pain receptors, activating neurotransmitters, sending a pleasure response to the brain and body. Immediate relief is exchanged for a drop in mood, which occurs when the chemicals in the body are no longer stimulated, providing that euphoric sensation. Higher dosages are then needed to achieve the same effect, as receptors become saturated from overuse.
One theory called the “changed set point” model describes the process of addiction from a point of view, which states that drug abuse alters the physiological setting or baseline of an individual. First, the neurobiology of dopamine, a neurotransmitter present in the brain regions that regulates movement, emotion, motivation, and the feeling of pleasure, has been altered, in addition to the ventral tegmental area (VTA), a group of dopamine-containing neurons that make up a key part of the brain reward system. In addition to these areas, noradrenaline (NA), a neurotransmitter produced in the brain that is involved in arousal and regulation of blood pressure, sleep, and mood (also known as norepinephrine) has been severely altered during early phases of withdrawal and abstinence, making it that much harder to quit an opiate addiction, once it has already gone underway.
Another explanation shares the cognitive deficit model of drug addiction, which proposes that individuals who develop disorders have abnormalities in an area of the brain called the prefrontal cortex (PFC). Important in regulating judgment, planning, and other executive functions, the PFC helps us overcome impulses for immediate gratification in favor of more rewarding, long-term goals; however, with some people, the PFC signaling to the mesolimbic reward system has been compromised.
Despite side effects like constipation, nausea and “pin-point” pupils, addicts continue to increase their dosage, escalating the level of dependence. Susceptibility to withdrawal becomes an increasing concern, as tolerance goes up, and the amount consumed increases significantly. Unfortunately, withdrawal is an inevitable phase in the recovery process from opiate addiction. Fortunately, there are other drugs like methadone, which are used to lessen the severity of the side effects of withdrawal.
The pleasure-reward system in the brain was designed to encourage particular “feel-good” behaviors inherent to natural life. Taking a bath, going on a walk, spending time with loved ones; these are all activities that reward the brain with dopamine. When the brain chemistry of an individual has been hijacked by opiates, providing a synthetic, more extreme high, the readjustment period may take some time. The addict may not feel the same highs as they once did as a result of the manufactured happiness. The long-term effects of enjoying life as it was meant to be experienced are well worth the adjustment — as is the acceptance of life in its most natural sense.