Drug dependence

Definition

A physical and/or psychological state, resulting from an interaction between a drug and organism, characterised by a compulsion to take the drug on a periodic or continuous basis to experience its psychic effects and/or avoid the discomfort of its absence

Psychological effects in dependence

wish

need

desire

craving

Physical effects in dependence

most marked with depressant
(inhibitory) drugs - opioids, alcohol

Addictive drugs

Depressants
(Psychological and Physical dependence)

Barbiturates

Opiates (heroin)

Alcohol

Stimulants
(Psychological dependence)

Amphetamines

MDMA

Cocaine

Cannabis

Hallucinogen

Inhalants

addiction mechanism

drug alters the physiological function of the organism and psycholigcal state of the subject

Continuous use develops tolerance

metabolistic or cellular

tolerance does not cause addiction,
but reinforces heavier or more frequent use

abstention from drug after abuse causes
physical and/or psychological withdrawal

patterns of use across countries vary depending on the availability of the chemicals and costs

Risk factors for drugs use

Dopamine & Reward

VTA

oppioids, alcohol, cannabis

Nicotine

works on nAChRs at the DA neurons in VTA

Mesolimbic (reward) pathway

Physical withdrawal

Psychological dependence

Non-addictive

Hypoxia

Glue

Solvents

Environmental

Genetic

Peer pressure

Unemployment

Childhood abuse

Formulation

mode of delivery

Personality traits

Impulse control

Risk-taking

Drug disposition

Pharmacokinetics

Pharmacodynamics

Psychopathology

Anxiety

Depression

Personality disorder

Stress responsivity

Drug induced neurochemical changes

work on inhibitory GABA neurons that
project to DA neurons in VTA

Anything that triggers release of DA
in the VTA can cause psychological addiction

DA neurons of the VTA projecting to the nucleus Accumbens

Cocaine & MDMA

work through blocking the uptake or increaseing
release of DA from presynaptic terminall

function of the reward system

reinforcing the positive behaviours

Sex

Food

Evidence for involvement
of DA in addiction

Intracranial stimulation in the VTA causes pleasure

D2 antagonists prevent that effect

Knock-out models

Physical dependence

normally inhibitory systems are balanced out by the excitatory systems

use of depressant drugs shifts that balance to the inhibitory side

abusing a drug causes the adaptation of the excitatory systems to match the the drug-induced levels of inhibition

Adaptation mechanisms

Receptor upregulation

increased NT synthesis

increased 2nd messenger concentrations

more depolarisations

Plasticity

Withdrawal

Withdrawal symptoms are the opposite
of acute effects of the drug

Caused by disrupted balance of inhibition/excitation (more excitation) in the absence of the drug

Heroin withdrawal

Withdrawal effects

Acute effects

Reflexes down

Secretions down

Feeling of warmth

Constipation

Cough down

Anxiety down

Aches and pains

Spontaneous muscle contractions (reflexes)

Tears, runny nose

Fever, goosebumps

Diarrhea

Coughing

Panicky

Heroin

effects mediated through the opioid receptors
in the forebrain, midrain and spinal cord

Alcohol

effects mediated through Ca2+ channels, GABARs and many other targets

very severe withdrawals

Pain relief

about 20% of patients stay clean after detox

association component

environment of the same friends or places, which were associated with drug abuse promotes the relapse

Anti-addictive therapy

Aversion theraphy

Substitution drug therapy

Clinical therapy

Methadone

Electric shocks used as a punishment for the drug use

Types of abusive drug users

Experimental

Recreational

Dependent

early stages

peers

choice

risk

Non-addictive

network

rules

mixed friends (users & non-users)

other life commitments

Addicts

experienced

friends are users

disrupted lifestyle

Soft/Hard

Soft

Recreational

Socially controlled

culturally conscious lifestyle

clubs, home use

Hard

addicted

Injecting

social and economic deprivation

inner city, street use

Reasons to try drugs

Availability

Curiosity

Peers

Context

Escape (for a while or forever)

Problems with the drug use

Infections (sharing needles)

Addiction

Cost

Drug habit is expensive, getting
the money often leads to crime

Social problems

Private and professional life

Mental problems

Psychosis, depression, anxiety

Revise drug mechanisms from 1st year notes