Addiction Medicine: Closing the Gap between Science and Practice

Addiction Is a Brain Disease..............................................................................................

Advances in neuroscientific research, including
animal studies and brain imaging, demonstrate
clearly that addiction is a primary and often
chronic disease of the brain.* 4 The risk factors
for developing the disease include a genetic
predisposition and a range of biological,
psychological and environmental influences.^5
There is a growing body of evidence showing
the brain circuits that are implicated in substance
addiction in general also are involved in other
compulsive or addictive behaviors such as those
related to gambling, certain forms of disordered
eating (e.g., bulimia, obesity) and compulsive
sexual activity.^6 For these reasons, researchers
are beginning to explore whether substance
addiction might be part of a syndrome
characterized by:

 Shared neurobiological and psychosocial
antecedents (risk factors);

 Production of desirable effects upon
involvement with the rewarding object or
activity;

 Shared manifestations and outcomes (e.g.,
biological ones such as tolerance or
withdrawal or behavioral or psychological
ones such as deceit, shame, guilt or
depression); and

 A shared course of the disease (e.g.,
improvement, relapse, remission and the
potential for progression to disability or
death).^7

• A primary disease indicates that it is not simply a

symptom or effect of another disease or condition.

The focus of this report is on addiction involving

nicotine, alcohol and other drugs. Use of these

substances can result from an existing brain

dysfunction; use also can alter the structure and

function of the brain, dramatically affecting

judgment and behavior.^8 The amount and

duration of substance use that results in brain

changes and addiction depends on the individual

and the particular substances used.† 9

As yet, there is no conclusive biological marker

of addiction; therefore the diagnosis of addiction

is based on its symptoms including the

compulsive use of addictive substances,

significantly impaired function and persistent

use despite negative consequences.‡ 10 These

symptoms that characterize addiction are

cognitive and behavioral manifestations of the

underlying disease and its effects on the brain.^11

The foundations of the disease may exist in

certain individuals even before they ever use an

addictive substance and, in some cases, once the

disease develops it persists even when an

individual is not actively engaged in substance

use.^12

† The addictive potential of a substance is

determined not only by its intrinsic ability to

stimulate the reward circuits of the brain, but also by

the speed with which it crosses the blood-brain

barrier (i.e., how soon after initial

ingestion/injection/inhalation it reaches receptors in

reward circuits of the brain).

‡ Other physical signs such as intoxication,

withdrawal, needle-related findings, co-infections,

and laboratory findings--such as abnormalities in

liver function tests or positive breath or urine tests--

can aid in the diagnosis.

Unfortunately, keeping the emphasis on just the

behavioral manifestations presumes that the

problem is present when the behavior is present

and the problem is resolved if the behavior is not

present for whatever duration of time, even

though the underlying disease process may be

present and even progressing, or contributing to

other manifestations, signs and symptoms that

may be overlooked.^13

...addiction is not about drugs, it’s about

brains. It is not the substances a person uses

that make them an addict; it is not even the

quantity or frequency of use. Addiction is about

what happens in a person’s brain when they are

exposed to rewarding substances or rewarding

behaviors, and it is more about reward circuitry

in the brain and related brain structures than it

is about the external chemicals or behavior that

“turn on” that reward circuitry.^14