Addiction

What is addiction?

Use of a substance
- at high doses
- when it is dangerous to do so
- despite harmful effects on self or others

What three factors interact with addiction

Psychological, biological, sociological

Rat Park Experiments

enriched v deprived environment
rats choose to drink morphine or plain water
looked at willingness to consume morphine or water
rats raised in deprived environment went for morphine, while enriched rats did not. They tried morphine sometimes but prefered water.
suggests that social enrichment plays a large role in likelihood of developing an addiction in animal models.

Effects of addiction on brain

Target mesolimbic reward system (nucleus accumbens, ventral striatum, amygdala, orbitofrontal cortex)
Dopaminergic pathway in brain - crucial for rewarding and reinforcing behaviour

Methamphetamine

mental effects (alertness, increased confidence, no appetite)
physical effects (fast heartbeat, increased bp, dilate pupils

how is methamphetamine addictive?

impacts nucleus accumbens, the primary reward centre in brain.
increases dopamine release by affecting presynaptic neurons - causes strong and longer high.
it damages dopamine terminals and causes shutdown of dopamine synapses - reduced function in brain centers needed for craving control and behavioural regulation

loss of dopamine transporters and meth dependence

participants in late abstinence had more available dopamine transporters that those in early abstinence.
negative correlation between the amount of methamphetamine consumed, years of use, and dopamine transporter availability

how does meth impact behaviour?

anhedonia - can’t experience positivity
reward seeking - searching for drug
motivational hijacking - manipulation of others, stealing to get money for drug
role disruption - neglect of social responsibilities in favour of drug seeking

cannabis effects

mental effects (euphoria, anxiety, impaired coordination and concentration, heightened sensory exp)
physical effects (dry mouth, nausea and vomiting, rapid heartbeat)

cannabis and the brain

cannabinoids act on endocannabinoid system eCS - plays a role in homeostasis and neuroplasticity
Effects mediated by CB1 and CB2 receptors in brain
CB1 receptors - cerebral cortex, hippocampus, caudate/putamen, substantia nigra, cerebellum
CB2 receptors - dopamine neurons of ventral tegmental area

case control study on cannabis

patients with psychosis - measured frequency and potency of cannabis use
found daily use of THC increases odds of psychotic disorder AND increased potency

Intertemporal choice

Addictions are problems of intertemporal choice.
Preference reversal can be applied to addiction to explain experience of someone with an addiction.

Cold v hot state

Situations where individual wants to stop but still consumes the substance
Intention is formed in cold state, but behaviour is executed in hot state- temptation completely changes behaviour.

Delay discounting

perceived decline in value of a reward based on the amount of time it takes to be released.
Those with opioid dependence have a higher delay discounting than healthy controls.

Temptation and abstinence

abstinent individuals believe they are not susceptible to environmental temptations
people who are not dependent on a substance cannot empathize with how difficult a temptation is
leads to belief that willpower determines likelihood of relapse rather than environment

COVID 19 and addiction

increase in overdose mortality, men higher
35-44 have highest prevalence, black people have the highest peak - non hispanic white and black swap pre covid

Overdose and type of drug

Illicit fentanyls and synthetics exponentially increase past 2015, especially after covid begins.