S3: Drug Dependence and Tolerance Flashcards
What is substance abuse?
Substance abuse is where a person consumes a drug in ways that are harmful to themselves or others.
List characteristics of drug addiction. How is drug addiction clinically defined?
It is a chronic relapsing disorder:
- Compulsion to seek and take drug.
- Loss of control in limiting intake.
- Emergence of a negative emotion state (dysphoria, anxiety, irritability).
Clinically: A maladaptive pattern of substance use leading to clinically significant impairment or distress as manifested by two (or more) of the following occurring with a 12 month period.
What book do psychiatrists used to diagnose addiction?
DSM-5 book.
List some factors that make an individual vulnerable to develop addiction
- Enviroment (stress is a big trigger).
- Drug induced effect causes neurochemical changes in the brain which can make individuals much more vulnerable to develop addiction.
- Genetic.
Describe how a mental health disorder can have co-morbilities with drug addiction
Drug abuse/dependence is found often with other conditions such as: Depression, anxiety, schizophrenia, PTSD.
- People abuse drugs because they may be addicted.
- Emotional disorder is a key predictor of alcohol use.
- Social anxiety disorders is severe in 60% of drug abusers seeking help.
- Metal health co-morbidity with drug addiction is accompanied by more sever systems, longer illness duration, higher service utilisation and higher relapse rate.
What is the difference between psychological addiction and physical addiction?
“Psychological addiction” = Drugs of abuse activate same brain systems as natural rewards and so are rewarding (make you feel good).
“Physical addiction” = To self-medicate withdrawal symptoms (e.g. dysphoria, cramping), common with heroin and alcohol.
What are the stages of drug addiction?
- Starts with peer pressure/ first time taking the drug. Peer pressure can reinforce and drive someone into taking a drug.
- Euphoric effect can be reached which encourages someone to continue
- Usually the cycle ends here (e.g. For individuals who smoke on nights out). However, some people develop tolerance where they need a larger quantity of drug to reach euphoric effect that they are seeking.
- Some people who develop tolerance then develop dependence.
- Initially, early in the addiction cycle it is the pleasure and the euphoric effect that drives the individual into taking the drug.
- At the later stage when you become dependent, it is the ‘self medication’ to get rid of the withdrawal symptoms that drives them to continue taking the drugs.
What is drug tolerance?
When a person’s reaction to a drug decreases such that larger doses are needed achieve the same effect.
What is drug dependence?
Drug dependence is an adaptive state that develops from repeated drug administration, and which results in emergence of physical and emotional withdrawal symptoms upon cessation of drug use.
Describe the symptoms of abstinence syndrome (LC) from drug dependence
- Physical: Sweating, gooseflesh (cold turkey), irritability, aggression
- The physical withdrawal symptoms are usually short-lived.
- Psychological, craving to avoid withdraw effects. They also suffer from emotional withdrawal symptoms such as extreme anxiety, depression, irritability, aggression and these withdrawal symptoms are long-lived and can last up to a year. These are motivational triggers to relapse.
Name and explain important areas in the brain involved in drug dependence
- Orbital frontal cortex –> motivational drive is what gives value to the reward.
- Nucleus accumbens and ventral pallidum –> reward centres of the brain and the reason we feel pleasure and these are activated in drug addiction.
- Amygdala and hippocampus –> learning and memory (and emotional learning) which is important in drug addiction.
- Prefrontal cortex and anterior cingulate cortex which are the executive centres in our brain which help us make judgements and decision’s. These are hugely affected in those who are suffering from drug addiction so their decisions may be impaired.
Describe how drugs ‘hijack’ the dopamine reward system
- Dopamine is a reward transmitter in nucleus accumbens. Drugs ‘hijack’ this system and stimulate this reward pathway at a higher level (compared to natural reward levels). This is positive reinforcement at encourages an individual to keep taking the drug to feel the euphoric effects.
- This can lead to dependence. The reward centres of the brain become supressed and not as much dopamine is released and everyday pleasures e.g. Food and sex will not activate these reward pathways. The drug will help stimulate the dopaminergic neurones to release dopamine and activate the reward pathway so the individual will seek the drug to feel the pleasurable effects again.
- This explains why sufferers may suffer from dopamine and low mood (emotional withdrawal symptoms) due to low dopamine.
List different acute targets (receptors) for different drugs
- Opiods: agonist at MOP, DOP, KOP receptors.
- Cocaine: Dopamine transporter blocker involved in reuptake of dopamine (so cocaine is an indirect DA agonist).
- Amphetamine: Dopamine release by displacing dopamine from their vesicles (indirect DA agonist).
- Alcohol: Facilitates GABA A inhibitory receptor and inhibits NMDA receptor function.
- Nicotine: Agonist at nACh receptors.
- Cannabinoids: Agonist at CB1 receptors.
- Phencyclidine: NMDA receptor antagonist.
- Hallucinogens: 5-HT 2A agonist.
- All these drugs activate the reward pathway, inducing the release of dopamine from NAcc. However, they do this from different mechanisms.
Describe Psychostimulant: Amphetamine
- Amphetamine like drugs like methylphenidate and MDMA release cytosolic monoamines.
- Amphetamines increases dopamine. It gets into the cell bouten via the dopamine transporter and displaces dopamine from synaptic vesicles, this is called “reverse transport”. The dopamine just then floats out through the transporter.
- Because amphetamines can get into the cells, it makes prolonged use neurotoxic. It causes degeneration of amine containing nerve terminals and cell death.
- Therapeutic uses include ADHD, appetite suppressants and narcolepsy.
List pharmalogical effects of amphetamines
- Increased alertness and locomotor stimulation (increased agression).
- Euphoria/Excitement.
- Stereotypes behaviour.
- Anorexia.
- Decreased physical and mental fatigue (improves monotonous tasks).
- Peripheral sympathomimetic actions (increase blood pressure and decrease gastric motility).
- Confidence improves/lack of tiredness.
