Addiction : The Neurochemical Explanation Of Nicotine Addiction Flashcards
Why is smoking rewarding?
- After nicotine enters the bloodstream it is transported to a part of the brain called the VTA. Here it binds with and causes excitation of receptors, called nicotine receptors, on the dendrites of the VTA.
- The VTA is a part of the brains reward pathway. It is responsible for generating feels or pleasure or the feeling of anticipation for an expected reward.
- The excitation of the nicotine receptors in the VTA leads to the release of dopamine into another part of the brains reward pathway called nucleus accumbens. The release of dopamine into the nucleus accumbens creates the rewarding feeling of pleasure. Explaining why smoking a cigarette is rewarding.
Why do smokers develop a tolerance?
- The longer a smoker smokes, the more nicotine they will need in order to get the same sense of reward from smoking. This indicates that tolerance has developed.
- Tolerance occurs because through repeated exposure to nicotine, the nicotine receptors become less responsive to nicotine (desensitisation). This means the binding of nicotine with the nicotine receptors causes progressively less excitation over time, which in turn means less dopamine is released into the nucleus accumbens. Consequently, a nicotine user needs to increase their nicotine intake so they can increase the activation of desensitised nicotine receptors.
Why do smokers experience withdrawal syndrome/become physically dependent?
- When a chronic smoker abstains from using nicotine for a sustained period, they can experience symptoms of nicotine withdrawal syndrome. This is evidence they have become physically dependant on nicotine.
- Withdrawal syndrome happens because chronic nicotine use causes the nicotine receptors in the VTA to become desensitised. Once the nicotine user then abstains, the combination of no nicotine and desensitised nicotine receptors means the body will struggle to activate there receptors with only its natural neurotransmitters. Consequently, the lack of activator on of the nicotine receptors in the VTA means there will be less dopamine than normal released into the nucleus accumbens, and this results in the negative feelings, like low mood, anxiety and cravings for nicotine, associated with nicotine withdrawal syndrome.
- To be physically dependant on nicotine, a persons body has to undergo physiological changes. One of these is the desensitisation of the nicotine receptors. Another is an increase in the numbers of nicotine receptors. This happens through a process called up regulation. Essentially, the brain compensates for the desensitized nicotine receptors by creating new receptors. This is called upregulation, as it leads to an increase in the number of available receptors. But after a while these new receptors will also be desensitised too. This results in more receptors being created, which in turn become desensitized too. This cycle continues, resulting in chronic nicotine users having many more nicotine receptors than non users.
What happens to smokers brain if they manage to quit for a sustained period?
It can take several months for the neurons in a chronic smoker to return to normal after they quit. Over these months, the nicotine receptors in the VTA return to their normal sensitivity, and the brain compensates for this by reducing the number of available receptors in the VTA (a process called downregulation). Through these changes, the reward pathway returns to a normal state of activity. This means the ex-smoker no longer has to have nicotine in order to feel reward and avoid withdrawal symptoms. It also means their tolerance to nicotine will be reduced (so if they do smoke again, they will need less nicotine
to experience the desired effect)
Why does neurochemistry provide a limited explanation for nicotine addiction?
For example, Karcher and Finn found that social factors, such as if an adolescent’s parents, siblings or close friends smoked, significantly increased the probability that the adolescent would also smoke. This finding demonstrates the importance of social factors for explaining why some people
develop a nicotine addiction. These social factors – along with all non-neurochemical factors – are
unaccounted for by the neurochemical explanation for addiction, demonstrating it offers only a partial explanation for nicotine addiction. However, just because the neurochemical level of explanation is not a sufficient explanation for nicotine addiction, it’s still a necessary part of the overall explanation. This is evident in the biopsychosocial model for addiction, which proposes that addiction be understood using a holistic approach, taking account of multiple levels of explanation that include biological (e.g., neurochemistry), psychological (e.g., cognitive) and social factors. Therefore, although the neurochemical explanation for nicotine addiction cannot fully explain nicotine addiction, it nonetheless provides an important part of the overall explanation for addiction.
What is a strength of the neurochemical explanation for nicotine addiction?
It has produced real life applications. These applications include drug treatments for addiction. For example, the drug varenicline has been shown to be three times more effective in helping people quit than placebo treatments. The effectiveness of drug treatments, like varenicline, for treating nicotine addiction demonstrate that the neurochemical explanation has been of practical use to society. This is because without an understanding of the neurochemistry of nicotine addiction, it would not have been possible to develop drug treatments, like varenicline, to treat the addiction. This also illustrates the economic implications of the neurochemical explanation for addiction. Nicotine addictions –primarily smoking – are very harmful to people’s health, and the illness this results in is a huge financial burden on countries like the UK. The fact that the neurochemical explanation can produce effective drug treatments will mean there will be fewer smokers and therefore less of a financial cost to the UK in terms of smoking related illnesses.
What is a strength of the neurochemical explanation for nicotine addiction?
It can work with the learning theory explanation to explain smoking behaviour in terms of compulsion loops. Compulsion loops occur when a person experiences an anticipation of reward when exposed to an environmental cue, leading them to complete a behaviour (e.g., smoking), which produces a reward that then reinforces the anticipation of reward associated with the original cue. Understanding brain neurochemistry helps partially explain the compulsion loop, as both the anticipation and feeling of reward can be explained by the release of dopamine in the reward pathway. Learning theory completes the explanation by showing how environmental cues (e.g., places like the pub) can, through classical conditioning, become associated with the rewarding feeling nicotine produces, leading to the cue reactivity experienced by smokers that initiates the compulsion loop. This illustrates of taking an interactionist approach to explaining addiction, one that considers the interaction of nature and nurture to give rise to a behaviour like nicotine addiction.
