Biological Explanation for Addiction

BIOLOICAL MODEL OF ADDICTIVE BEHAVIOUR

• View addiction as a disease
• Physical Dependence Theory - person cannot cope with out engaging in addictive habit
• Develop Tolerance - biological resistance, they have to engage more often in order to get desired effects.
• Detoxification is the withdrawal from addictive habit which can result in withdrawal symptoms.

BIOLOGICAL MODEL OF SMOKING

Genes + Dopamine System (Initiation)

AO1

• Addiction occurs due to inheriting genes that increase likelihood of initiation of smoking.
• Individuals with A1 variant of d2 Dopamine Receptors (D2DR) have fewer/insensitive dopamine receptors.
• Dopamine is associated with feelings of happiness.
• Smoking increases release of dopamine compensating for deficiency.
• Smoker associate pleasant feeling/happiness with smoking.

AO2

• Thorgiersson, Meta-Analysis of 140,000 people, research link between smoking and genetic variants. Found specific genetic variants associated with whether people start smoking / how much / and how difficult it is to quit.
• Rigorously controlled/ Reliable, so many participants
• However genetic variant makes it more likely people will smoke, does not mean they will smoke, other factors involved.
• Correlation study, no causation, could be a third variable.

• Comings et al, found 48.7% of smoker carry a1 variant of D2DR compared to general population, 25.9%.
• same gene variant also associated with autism and tourettes so cannot simply be a reward based explanation for smoking.

• Volkow gave a group of adults Ritalin which raises levels of dopamine. Brain scans show those who enjoyed the Ritalin had lower D2 Dopamine receptors than participants who disliked the Ritalin.
• This shows some people are particularly vulnerable to the rush caused by dopamine enhancing drugs thus likely to develop and addiction/relapse.

NICOTINE REGULATOR MODEL (MAINTENANCE)

AO1

• Smokers maintain nicotine levels to avoid withdrawal symptoms, CHEMICAL ADDICTION.
• Nicotine activates nicotinic acetylcholine receptors in the brain causing release of dopamine.
• Causes feelings of pleasure for smoker, when nicotine levels drop mood/focus is impaired, smoking again will alleviate withdrawal symptoms.

AO2

• Shachter, two group of participants gave one group low nicotine cigarettes, the other high nicotine cigarettes. Those on low nicotine cigarettes smoked 25% more than those on high nicotine cigarettes.
• This shows smokers smoke in order to maintain high levels of nicotine.

DOPAMINE REWARD SYSTEM (MAINTENANCE)

AO1

• Nicotine increases dopamine levels in neural pathways of the brain associated with brain reward system.
• High levels of dopamine provide positive feelings.
• Maintaining nicotine levels maintains positive feelings.

AO2

• Corrigall + Cohen  allowed rats to self-administer nicotine, injecting rats with drugs blocking release of dopamine reduced their addiction to self-administrate nicotine.
• This shows dopamine system is involved with addictive behaviour.

CUE REACTIVITY + REDUCED SELF-CONTROL (RELAPSE)

AO1

• Prolonged exposure to nicotine leads to long term reduction of dopamine in the brain.
• Addicts learn to associate cues (such as smell of tobacco, or the packaging of cigarettes) with the reward caused by nicotine, exposure to cues can cause relapse.
• smoking impairs frontal cortex, involved in decision making and thus lack self-control and ability to quit habit.

AO2

• Lerman et al,…