Chapter 9, Addiction Flashcards
Substance Use Spectrum
Non–> Beneficial use–> Lower-risk use–> Higher-risk use–> Addiction
“War on Drugs”
- 1970: Controlled Substance Act (CSA) established five schedules of controlled substances and created the Drug Enforcement Administration (DEA)
Current Canadian Perspective on Drugs
Canada has the Controlled Drugs and Substances Act (1996) which classifies drugs, their precursors, and devices into 9 drug schedules (though some schedules have been repealed with the legalization of cannabis)
Addiction
- A chronically relapsing disorder, characterized by compulsion to seek and take the drug, loss of control in limiting intake, and emergence of a negative emotional state when access to the drug is prevented
- APA has stopped using the terms addict and addiction
Addiction symptoms
Addiction usually consists of:
* Physical dependence
* Compulsive drug seeking (driven by craving)
* Periods of remissions and relapse are common
Substance Disorders
The Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM-5) defines substance-related disorders for 10 classes of drugs
* Substance use disorders: A cluster of cognitive, behavioural, and physiological symptoms indicating that the individual continues using the substance despite significant substance-related problems
* Use of a drug is NOT a substance use disorder unless it leads to significant impairment or distress
* There is no single criterion for determining a substance use disorder
* Substance-use disorders may be classified as mild, moderate, or severe, depending on the number of criteria met
Areas impacted by the disorder diagnosis criterion
- Impaired control
- Social impairment
- Risky use
- Pharmacological dependence
Pathological Drug Use
- Preoccupation/anticipation
- Binge/intoxication
- Withdrawal/ negative affect
Older Models of Addiction
- Moral model of addiction
- Addiction is caused by poor choices, weak will, and/or personal failing
- Hedonia theory of addiction
- Addiction is caused by the fact that drugs are positive reinforcers
- Psychological model of addiction
- Addiction is caused by psychological disturbance and/or is a coping mechanism for psychological problems (self-medication hypothesis)
- High rates of comorbidity with SUD
The Disease Model of Addiction
Also known as the medical model of addiction, the disease model of addiction considers addiction to be a distinct medical disorder or disease
The Reward Circuit
- Reward circuit: Neural circuit responsible for the acute rewarding and reinforcing effects of abused drugs.
- A number of brain regions form an integrated circuitry responsible for learning, motivation, and the control and direction of behaviour – the Mesocorticolimbic dopamine (DA) system
- Activation of the mesolimbic DA pathway from the VTA to the NAcc plays a central role in reward and reinforcement
- Virtually all drugs of abuse increase DA in the striatum and nucleus accumbens
Natural Reinforcers vs. Drugs
Both activate the mesolimbic DA system via:
1. Direct excitation of the VTA
2. Indirect stimulation of excitatory (glutamatergic) input to the VTA or NAcc
3. Indirect blocking of inhibitory (GABA) input onto the VTA or NAcc
Natural Rewards
Natural rewards (such as food or sex) also activate the mesolimbic DA system but…
* Natural reinforcers have satiety mechanisms (I’m full)
* Drugs produce much higher and much faster surges in DA release
* Natural rewards may become less motivating for drug addicts, even after long periods of abstinence because of long-term changes to the DA system
Dopamine Theory of Addiction
- Alterations in dopamine function are involved in the various phases of drug addiction; dopamine as the “pleasure” neurotransmitter
- This theory fit particularly well for the stimulant class of drugs
The Role of Dopamine
- Historically, we thought that dopamine was responsible for feelings of pleasure, but…
- In trained animals, DA spikes in response to a cue rather than in response to the reward
- Animals with extensive damage to DA neurons will still display hedonic reactions
- Electrical activity of DA neurons in VTA recorded as monkey completes a discrimination task
- VTA is the origin of the mesocorticolimbic DA pathway
Results:
* Initially, DA neurons fire in response to reinforcers in environment
* With training, DA signal shifts to prediction signal and fires upon presentation of CS
* With training, DA is depressed when a reward is expected but not presented
“Liking”
- Liking can be inferred from behaviour
Animals with low DA will choose less effort. Both animals show levels of ‘liking’ in response to eating the food. - Berridge and Kringelbach (2008) argue that the “liking” system is focused on restricted hedonic hot spots
- Although DA plays a central role in drug reward, evidence suggests that other neurotransmitter systems must also be involved, such as the endogenous opioid and cannabinoid systems
Liking vs. Wanting
- Separate neural circuitry for liking and wanting…Liking refers to an emotional state whereas wanting has more to do with motivation and decision utility (Berridge and Aldridge, 2008)
- Liking = hedonic impact = pleasure, euphoria
- Wanting = incentive salience = motivation, wanting
- The incentive sensitization theory posits that repeated drug use sensitizes the wanting of the drug (but not the liking of the drug)
- Drug cues may gain enhanced salience, further promoting drug wanting
The Incentive Sensitization Theory of
Addiction
- Repeated drug use leads to an increase in wanting the drug (i.e. craving) but no increase in drug liking (reward or euphoria); only the “wanting” becomes sensitized
The Biopsychosocial Model of Addiction
- Considers biological, social, and psychological factors in addiction
- Genetic variation
- Psychosocial variables: Level of education (less education = greater risk), Lack of employment, Lower age, Exhibiting conduct problems during childhood, Having substance-using friends, Stress and ability to cope with stress, Anxiety, mood, or personality disorders
- Factors that promote the likelihood of substance misuse and factors that decrease the likelihood of substance misuse are considered
The risk of relapse may be reduced by:
- Moving to a new area
- Developing new relationships with non-users
- Obtaining employment
- Using other activities such as exercise or meditation
