The biological model into addiction

The biological model into addiction

1. Relapse: PFC and withdrawal symptoms

   • A01
     • Pre frontal cortex thought to serve an executive function in the brain, by acting as a 'gate'
     • PFC inhibits/moderates the drive to respond to immediate reinforcements which may have LT negative effects
     • Addicts are thought to have an impaired PFC, and so are unable to make good decisions
       • End up relapsing due to poor decision making
     • The abstinence from the addictive behaviour can cause witthdrawal symptoms
       • The desire to eliminate these withdrawal symptoms causes the addict to then relapse (-ve reinforcement)
   • A02
     • Claridge and Davis: Unclear whether the impaired PFC is a result of over activation/drug use, or if there is a tendency for addicts to have an impaired PFC initially and this increased the risk of them being addicts
     • Smoking
       • Grunberg: Nicotine withdrawal is associated with increased irritability and weight gain
     • Gambling
       • Grunberg: Gamblers miss the psychological rewards of stress reduction associated with gambling activities

2. Initiation: Genetics

   • A01
     • Heritability of addictive behaviours can be studied through twin and family studies
     • Multiple genes can result in physiological abnormalities, which predispose an individual to addiction
     • Merikangas et al: 36% of relatives of the individuals with alcohol disorder, had also been diagnosed with an alcohol use disorder.
       • Further support the theory of genetics being an important factor in the initiation of addictive behaviour
     • A1 variant of DRD2 gene causes fewer dopamine receptors to be present in the mesolimbic dopamine system. This results in more dopamine needed to create the same effect as someone with a 'normal' number of receptors because dopamine effect is felt less.
   • A02
     • DRD2 gene common in autistic people. Autistic people don't show addictive behaviours, so link between DRD2 and addiction is more complex as the gene cannot be sole factor causing addiciton
     • Not complete explanation - you may be predisposed, but don't get addictions unless environmental factors trigger onset
       • Diathesis stress model provides a sound explanation as those with genetic predisposition may not get addicted unless there's an environmental trigger e.g. stress
     • Deterministic as not all who are predisposed and partake in addictive behaviour become addicted
     • Smoking
       • Comings: found 48.9% of smokers had A1 variant of DRD2 gene and 25.9% of general population had the A1 variant
         • Suggests A1 variant more common in smokers, so could be cause of their addiction
       • Silverstein et al: Found that biological factors may influence a person's first postive and negative experiences with cigarettes, affecting their likelihood of becoming a smoker
     • Gambling
       • Black et al: First degree relatives more likely to gamble
       • Shah et al: Evidence of genetic factors in men who gamble

3. Maintenance: Dopamine

   • A01
     • Dopamine is a neurotransmitter which induces the feeling of pleasure and euphoria
     • When you carry out a behaviour that is pleasurable, dopamine is released, telling the brain to do the behaviour again (Leshner)
     • Non-adaptive behaviours can also stimulate release of dopamine e.g. sex, eating. Chemicals like amphetamines can also increase dopamine levels
     • A desire is now there to do the behaviour again, even when the substance/behaviour is absent, the desire can still persist (incentive sensitisation)
     • As you continue to carry out the behaviour, down-regulation occurs. This is when more dopamine is needed to create the same effect you initially got
   • A02
     • Small et al: brain imaging showed an increase in regional blood flow in parts of mesolimbic system when pps ate chocolate. Same regions activated when highly motivated to eat chocolate
       • Supports the dopamine reward pathway
       • Increased confidence in validity of theory
     • Reductionist explanation as it ignores social, cognitive and environmental factors that may also contribute to addictive behaviour
       • Did lead to effective treatments, so perhaps better as a reductionist
     • Suggests that dopamine sensitivity inevitably leads to addiction
       • Volkow et al: individuals who live in a stimulating environment may be protected from addiction, as they don't need to seek for pleasurable activities to do. Those in boring environments may turn to other non-adaptive behaviours to get euphoria and thus dopamine.
     • Smoking
       • Schachter et al: The nicotine-titration model suggests smoker smoke to maintain a level of nictoine in their system
     • Gambling
       • Shinohara et al: raised levels of dopamine occur in social gamblers when they are gambling and in anticipation of gambling
         • Suggests learning processes and biology are involved in gambling dependency