Friday, February 22, 2019
Ã¯Â»Â¿Genetic explanations Essay
transmittable explanations for the Initiation of addictionsHeritability of addictions such as alcoholism and frolic can be studied through family and twin studies. The presumptions of twin and family studies argon that if family members partake in similar demeanors, thus the degree to which the demeanors be slipd by divisortical factors can be examined. There ar two types of check, identical and non-identical. resembling tally are monozygotic (MZ) as they came from the analogous egg, and therefore share an identical set of genes. Non-identical twins are dizygotic (DZ) as they light from two different eggs that were fertilised at the same time, and as a result their genes are no more alike than any sidekick or sisters. Twins can also differ in the environs that they are brought up in. Some twins whitethorn, rarely, be separated at birth and therefore have very different upbringings. If researchers are able to find MZ twins who have been raised apart (i.e. same gen es but different environments) then they will be able to name among the influence of genes and environment on a certain demeanour.If MZ twins who have been raised apart booth show the same demeanour, then the behavior is probably genetic but if only one of them has that demeanor then it may well be caused by the environment. The degree to which twins and family members share a behaviour is termed a agreement rate, with 1 (or speed of light%) being entirely genetic, and 0 (or 0%) being entirely environmental. McGue (1999) ap prove a concordance rate of 50-60% for alcohol addiction, and Agrawal & Lynskey (2006) found a concordance rate of 45-79% for addiction to illicit doses. This means that just over half(prenominal) of the factors that cause addiction to alcohol are genetic in origin, as are half to three-quarters of the factors causation addiction to illegal medicates. A paradox with this conclusion, however, is that the genetic link may be for behaviour disorders rather than addiction, and these behaviour disorders may manifest as some anti well-disposed behaviours including alcohol and drug use.The sensitiveness of the dopamine system is one biological explanation for the imitation, sustainment and relapse of habit-forming behaviours (see below), and so it would make sense for researchers to look for genes that are responsible for causing particularly sensitive or insensitive dopamine systems. One such gene is called the DRD2 gene (or dopamine receptor niggardliness 2 gene). The DRD2 gene codes for the number of dopamine receptors available in the mesolimbic dopamine system.A person with fewer dopamine receptors isunable to feel the effectuate of dopamine as well as someone with a higher(prenominal) number of dopamine receptors, and so call fors higher levels of dopamine to realize the same effect as a person with more dopamine receptors. People with the DRD2 A1 variant of the gene have fewer dopamine receptors, and also seem more v ulnerable to addictions. Evaluation for genetic explanations of habit-forming behaviourGenetic inheritance may explains individual differences in addiction Genetic inheritance can, through the diathesis-stress influence, explain why some people arrive addicted whereas former(a)s in the same environmental situation do not. The diathesis-stress model is the idea that a genetic vulnerability may manifest in the right circumstance e.g. if a person who is susceptible to becoming addicted, delinquent to their genetic inheritance, is suffering from some form of stress or boredom due to environmental factors, then they may partake in an addictive activity. further this is a very deterministic view of human behaviour that ignores environmental factors, as not all people with the A1 variant of the DDR2 gene become addicted even if they partake in a potentially addictive activity.Inconsistent research findings linking specific genes to addictions Noble (1998) found affirm for the DRD2 A1 gene being linked to alcoholism (the gene was found to be carried by 48% of severe alcoholics, 32% of less severe alcoholics, and 16% of non-alcoholic controls), but many other studies have failed to find such a link. Specific genes are linked to other disorders as well as addiction The DDR2 A1 gene is also common in people with autism and Tourettes, as well as in people with addictions. Autism and Tourettes sufferers are not enjoyment seekers and do not tend to suffer from addictions, and so the link between the A1 variant of the DDR2 gene and addictions is unclear and far more complex than exclusively claiming that the gene causes addiction.The dopamine model of addictionInitiation of addictive behaviourDopamine is released in the mesolimbic dopamine system of the brain, to signal reinforcer and pleasure. If a behaviour causes dopamine release then the brain knows to do it once more e.g. eating, drinking, keeping warm, having sex these are adaptive behaviours in evolutiona ry ground as they help anorganism/species to survive in its environment. Unfortunately other non-adaptive behaviours (i.e. behaviours that do not necessarily aid survival) can release colossal amounts of dopamine (e.g. gambling and drug taking). Certain chemicals (e.g. amphetamines, alcohol, cocaine) can directly cause huge amounts of dopamine to be released. The effect of this dopamine release is to disunite the brain that the behaviour is desirable and that it should seek to DO IT AGAIN And check to incentive sensitisation theory, desire for the rewarding magnetic core or behaviour persists even in the absence of the substance or behaviour.Maintenance of addictive behaviourRepeated exposure to an addictive behaviour or substance causes reduced sensitivity to the dopamine release through a branch known as down regulation. This means that more of the behaviour is necessitate to cause the same pleasurable psychological effect in the mesolimbic dopamine system. Stopping the beh aviour altogether creates a state of disequilibrium in the dopamine system, and leads to withdrawal symptoms that can only be reduced by reiterate the (now learned) behaviour. This disequilibrium, an increased need for dopamine stimulation, and the unpleasant withdrawal symptoms it causes now social movement behaviour so that it is no longer pleasure (positive reinforcement), but the need to reduce withdrawal symptoms (negative reinforcement) that drives the addicts behaviour.Relapse of addictive behaviourWhen an addict finally manages to stop engaging in a behaviour or taking a substance, they are at risk of relapse. harmonize to the dopamine model, relapse can be explained by addiction causing permanent brain changes that lead to lasting memories of the substance or behaviour. environmental reminders of the addiction (e.g. being in a pub, watching horse racing, returning(a) to a location where drugs were taken, being under stress) can release broken amounts of dopamine, which in turn lead to the addicted person desiring a great dopamine reward that can only be obtained by re-engaging in the addictive behaviour Evaluation for the dopamine model of addiction moderate for the dopamine model of addictionSupport for the dopamine model comes from many experimental studies, such asa study into the effects of methylphenidatee (Volkow, 2001). Volkow gave a drug called ritalin to healthy volunteers and correlate their subjective experience of the drug with the density of dopamine receptors in their mesolimbic dopamine systems. Those that reported pleasurable feelings with ritalin had fewer dopamine receptors than those that hated its effects. This supports the theory that some people are more vulnerable to the effect of dopamine-releasing drugs than others.Neurochemical explanations ignore social factorsAn important point to note is that neurochemical explanations for addiction (e.g. the dopamine model) ignore social and environmental factors that may also contri bute to addictive behaviour. However, they can lead to effective treatments for addictions, e.g. permutation cigarettes with nicotine patches.Implications from animal researchGrant et al (1998) found that animals that lost social status also lost dopamine receptors, and offers therefore a assertable explanation for social-class based addictions (e.g smoking in lower socio-economic groups). However, animal studies may not be generalisable to human addictive behaviour. Inevitability of dopamine sensitivity leading to addiction The dopamine model suggests that reduced dopamine sensitivity, as caused by fewer dopamine receptors, inevitably leads to addictive behaviour. However, there is believably to be a complex interaction between an individuals specific environment and whether or not dopamine sensitivity leads to addiction. A stimulating environment may provide enough dopamine reward to protect people from addiction, whereas a dull or boring environment may not (Volkow, 2003).Neur ochemical explanations are reductionistNeurochemical explanations for addiction reduce addictive behaviour to a simple variance in the structure of the dopamine system, and so ignore social and cognitive factors that can influence addictions. However they can lead to effective treatments, so in this case it is useable to be reductionist.