All addictive drugs produce their effects by
altering the synaptic activity.
Show video “World’s most dangerous drug”
Humans engage in behaviors that are
rewarding; pleasurable feelings provide
positive reinforcement so that the behavior is
There are natural rewards and artificial
rewards, such as drugs.
Natural rewards reinforce behaviors required
for survival. (food, water, sex, nurturing)
The reward pathway is in the limbic system
consisting of the nucleus accumbens, ventral
tegmental area (VTA) and the prefrontal cortex.
The neurons of the VTA contain dopamine which is
released into the nucleus accumbens and
prefrontal cortex in response to natural or artificial
Stimulation of the reward pathway produces
highly pleasurable sensations, providing positive
reinforcement which promotes further drug use.
As Travis said: Addiction is a state in which a person
engages in a compulsive behavior, even when
faced with negative consequences.
The behavior is rewarded and reinforced via the
A major feature of addiction is the loss of control in
limiting intake of the substance or behavior.
Addiction is a chronic, relapsing disease resulting
from fundamental changes in the brain.
When a substance is used repeatedly over
time, tolerance may develop.
The brain adjusts its chemistry to offset
the effects of the drug and tolerance
As tolerance develops, more of the drug is
needed to produce the same effects.
Substance dependence develops when
neurons adapt to repeated drug use and only
function normally in the presence of the drug.
When dependency develops, the brain has
become dependent upon the substance to
Without the substance the user experiences
withdrawal and intense cravings for the
It is possible to be dependent on a drug
without being addicted. Although, if one is
addicted they are most likely also dependent.
For example; A terminal cancer patient being
treated with morphine for pain will experience
withdrawal if the drug is stopped, but they are
not a compulsive user of the drug therefore
they are not addicted.
Drug addicts and overeaters experience similar
responses in the reward pathway.
Image of nucleus accumbens in the reward
center: red=high dopamine receptors, yellow &
green=lower dopamine receptors.
With less dopamine receptors a person has
difficulty feeling joy.
Scientific studies have revealed that the brain
activity of alcoholics and drug abusers is very
similar to that of compulsive gamblers and
Prolonged drug use causes the dopamine
neurons in the reward pathway to cease
This state of dopamine deficiency causes the
user to experience chronic feelings of
anxiety, depression and an inability to just
The person can only feel normal when under
the influence of the drug.
Continued drug use causes long-lasting, even
permanent, changes in the functioning of
Long-term drug use alters the brain in
fundamental and long-lasting ways. (normal
brain vs. meth brain)
Addiction is a disease of the brain.