ADDICTION
THE PRINCIPLES
I.
Addiction is the repetitive, compulsive use of a substance despite negative consequences to the user.
2.
Addictive drugs initially activate circuits in the
brain that respond to
normal pleasures, like food and sex. Every brain
has these circuits, so every human
could potentially become addicted to a drug.
3.
Drug taking persists for many reasons, including
changes in the brain, the desire to experience pleasure from the drug, and the desire to avoid the discomfort of withdrawal.
4. Many different factors
in the life of an individual, such as family history,
personality, mental health, social and physical environment, and life experience, play a role in the development of
addiction.
WHAT IS ADDICTION?
Addiction (or psychological
dependence, as some people call it) is the repetitive, compulsive use of a substance by a person despite negative
consequences to his life and/or
health. Use of cocaine or heroin is illegal and unhealthy, but not everyone who uses those substances is addicted to
them. Likewise, addiction differs from physical dependence: simply undergoing changes when substance use is stopped
(like the headache that many coffee
users experience when they miss their morning cup of coffee) is a sign of physical dependence, but it is not necessarily a sign of addiction. Both psychological dependence and
physical dependence coexist in people
who are strongly addicted to some drugs.
This definition of
addiction obviously applies to the compulsive, repetitive use of alcohol, nicotine, and opiate drugs
like heroin, as well as cocaine and
other stimulants. But what about activities like overeating, gambling, and sex? Some people engage in these
activities to the point that there are
negative consequences for themselves (and their families). Some people gamble away everything they have, or
engage in promiscuous sex to the
extent that they risk infection with HIV or other sexually
transmitted diseases. These behaviors resemble drug-seeking behaviors in an addicted person, and more and more research
shows that the same neural circuits
may be involved.
HOW
ADDICTION STARTS: THE NEURAL CIRCUITS OF
PLEASURE
What would lead
someone to abandon his job, his family, and his life or to ignore the most basic, life-sustaining impulses to
eat and reproduce? There must be
something fundamentally different about "addicts" that leads them into such an extremely dysfunctional
lifestyle. Addiction has been
attributed to personal characteristics, including a lack of "morals,"
having different brain chemistry,
experiencing mental illness or extreme trauma,
or hanging out with the wrong friends. While all of these factors influence addiction, something more primal is at
work. The neural mechanisms by which
addictive drugs act are present in every brain. Addiction is so powerful because it mobilizes basic brain
functions that are designed to
guarantee the survival of the species. Because these mechanisms exist in every brain, potentially any human being could
become a drug addict. The reason lies
in a complicated neural circuit through which we appreciate the things that
feel good. The job of this neural
circuit, presumably, is to cause us
to enjoy activities or substances that are life-sustaining. If it is successful, then it is more likely that we will
engage in the activity again.
How
does this "pleasure circuit" work? Let's use food as an example. If a
person has a really great pastry at a
bakery, he will go to this bakery again because the food tasted good. The good-tasting food is a reinforcer
because it increases the likelihood
that the person will engage in the same behavior (going to the bakery). Animals, including humans, will work to obtain access to food, water, sex, and the opportunity to
explore all environment (perhaps to
find food, water, or sex). These are the "natural reinforcers"— events or substances in the world that motivate
behavior.
In a laboratory, animals can learn to press a lever to obtain a food pellet. This is the laboratory equivalent of the bakery scenario. There is a critical neural circuit in the brain that makes
this happen. If this circuit is damaged,
even animals that arc extremely hungry will not press the bar. We think that this neural circuit is the pathway
that causes the animal or person to
experience the reinforcers as pleasurable. It is sometimes called the reward pathway. When this pathway is destroyed,
an animal loses interest in food, in
sex, and in exploring its environment. It is still capable of doing all these things; it is just not
motivated. On the other hand, an animal
will work very hard (pressing a bar or
whatever) to turn on a gentle
electrical current that stimulates this pathway. It acts like it enjoys having the pathway stimulated electrically. This is
called self-stimulation.
