PSY260 Lecture 12: Addiction

Addiction

• A chronic medical condition involving complex interactions among brain circuits, genetics, the environment, and an individual’s life experiences

• People with addiction use substances or engage in behaviours that become compulsive and often continue despite harmful consequences

What is considered addictive?

• Some illicit drugs

  • Heroin, cocaine, amphetamines

• Some legal drugs

  • Caffeine, nicotine, marijuana

• Many behaviours

  • Shopping, stealing, skin/hair picking, social media use, gambling, exercise, work

  • Anything involving dopamine

• There is not a clear line between what is/isn’t addictive

Drug Abuse: Terminology

• Language of drug abuse tends to frame addiction as the user’s fault

• Reality: societal norms play a huge role in what gets called abuse

• Drug abuse is not the same as addiction

  • More related to dose and legality

  • Line is a bit blurred and differs for different substances

  • Ex. smoking a single joint is abuse in countries where it’s illegal

  • Ex. using a prescription drug for something it wasn’t prescribed for is also “abuse“

What Factors Lead to Addiction?

• Almost every addiction is a result of an individual trying to cope with something

1. Trauma

   1. Attachment wounds

   2. Social isolation

2. Neurotransmitter dysregulation

   1. Ex. in ADHD → lack of dopamine

3. Pain management

   1. Emotional/physical pain

   2. Especially opioids

Using Drugs: Development

• Development is a large factor

  • Late adolescents (~17-22) are the largest group of drug users

• Reasons

  • PFC is still developing

    • Inhibitory control not fully developed

    • Not all executive functions are online

  • Ventral striatum is dominant → reward-seeking

Famous Psychologists who used Drugs

• Sigmund Freud

  • Advocate for medical use of cocaine

  • Likely met modern criteria of addiction, eventually quit

  • Died from complications related to drug use

• Carl Jung

  • Experimented with psychedelics for research

  • Probably not considered addicted by today’s standards

  • Likely drug abuse due to illegality

• William James

  • Documented experience with laughing gas

  • Not considered addicted or qualify as drug abuse (made illegal later)

Positive Reinforcement in Drug Abuse

• For someone to choose to take a drug a second time, they often have a high level of positive reinforcement while taking it the first time

  • Taking the drug increases a positive feeling → chasing the “high“

Incentive Salience Hypothesis

• Dopamine is considered the physiological bases for “wanting“/”motivation”

• Anything that increases dopamine → increase “wanting“

  • Becomes addictive

Reinforcement: Nucleus Accumbens

• Addictive drugs lead to increased dopamine release in the nucleus accumbens (ventral striatum)

  • Some directly increase dopamine levels

    • Cocaine, amphetamine

  • Some prevent inhibition of dopamine release

    • Heroin

Reinforcement: Brain

• One theory: large dopamine released “moves“ from nucleus accumbens (ventral striatum) to dorsal striatum (habit learning/operant conditioning)ay May result in compulsive use → becomes a habit

  • Moves from front → back

  • Users may describe not even enjoying the drug → more just feeling like they have to take it

Allostatic Model

• Chronic exposure to addictive substances leads to neuroadaptations in the brain’s stress and reward systems

  • Emphasizes the role of stress-related pathways and negative reinforcement in the maintenance of addictive behaviours

  • Baseline dopamine levels increase → keep taking drugs to reduce negative state (negative reinforcement)

Administration Matters

• Large, rapid spike in dopamine in the nucleus accumbens is the hallmark of an addictive drug

• Importance in dose and route of administration

  • Rapid delivery via bloodstream → higher addictive potential

  • Ex. slow-release opiate after surgery is less addictive than injecting heroin

  • Ex. taking Adderall (amphetamine) pills is less addictive than smoking amphetamine

    • Same substance still differs in addiction potential with different routes of administration

Tolerance

• Reduced reaction to drug, so that larger doses are required to achieve original effect

  • Links to habituation (decrease in strength/occurrence of a behaviour due to repeated exposure to stimulus)

• Role of Pavlovian Conditioning

Pavlovian Conditioning in Addiction

• Experienced crack cocaine users show conditioned compensatory response to placebo crack

  • Conditioned compensatory response: body attempts to self-correct before expected spike

• Gave rats placebo coke and saw that their heart rates dropped → their systems were prepping for the spike of real crack

  • After real crack → spike

  • Less severe because of conditioned compensatory response

Cross-Tolerance

• If a drug user becomes tolerant to one drug, the user may very well have tolerance for another, related drug

  • Related to generalization

• Depends what type of neurotransmitter is involved

  • Ex. someone on an antidepressant (affecting serotonin transmission) → feel less if they take MDMA (which also works through serotonin transmission)

    • Same NT affected → generalization

Sensitization

• Increased reaction to drug at the same dosage

  • As opposed to tolerance (decreased reaction)

Tolerance vs. Sensitization

• Hypothesized that:

  • How much someone “likes“ a drug → tolerance

    • ↓ “liking“ with time (habituation)

  • How much they “need“/”want” the drug → sensitization

    • ↑ “needing/wanting“ with time (sensitization)

Sensitization: Rodent Locomotion

• Rats injected with the same dose of amphetamine every day increased response (step counts) with time

  • Sensitized → same amount of same drug was increasing outcome

Withdrawal

• After taking a drug for a prolonged period of time (whether addicted or not) → period of withdrawal occurs

  • Associated with negative symptoms: nausea, vomiting, muscle aches, anxiety etc.

• Negative reinforcement: continue taking drugs to avoid withdrawal

Other Factors for Addiction

• Memories about the drug may be particularly strong due to emotional learning (powerful encoding)

  • Memories surrounding drugs often have a powerful emotional component so they are better remembered

• Adrenaline/noradrenaline rush when taking a drug → can lead to enhanced memory for circumstances around taking drugs

  • if strong positive → can make you want to do it again

Addiction Summary

• Popular theories of addiction focus on many elements of learning

  • Habituation, sensitization, classical conditioning, operant conditioning, role of dopamine, role of emotions, etc.

• Hypothesize that the learning circuits in the brain are “hijacked” by addiction

• “Natural” reinforcers are no longer good enough — only the drug will do