Relapse, Craving, and Reinstatement

Drug abuse is a relapsing disorder. In fact, most drug abusers and

addicts have stopped or tried to stop taking drugs, only to eventually

relapse. So at any given time, most drug abusers are in fact relapsers.

Therefore, it is important to study relapse itself, and this is nicely

done in a variant of the self-administration model, as mentioned pre-

viously. It works by allowing the animal to learn to self-administer a

drug, such as cocaine, until the lever pressing is stable. Then, the

drug is withdrawn, and, as expected, the animal gradually tires of

lever pressing without a reward and the lever pressing behavior is

extinguished. This animal is now an experienced drug user, much like

most humans who have used drugs but have stopped. A human in this

condition likely thinks about the drug, and when stressed or

reminded of the drug, perhaps by some cue, craves the drug and per-

haps starts looking for a drug. The cue can be the sight of friends who

use drugs, the crack house, or even some white powder that reminds

him or her of the drug. Cues and their effects are very interesting and

currently studied. For example, Drs. Leslie Lundahl and Chris-Ellyn

Johanson recently found that drug-related cues set off cravings in

marijuana-dependent subjects.5 Getting even a small amount of the

drug (which is a cue) might set off a binge of drug taking. So, as you

can see, certain events can trigger craving, drug seeking, and relapse.

Now, let’s return to the animal that has experienced a drug but is

currently without it. If stress, such as a foot shock, is present or if the

drug is injected, the animal remarkably starts to press the lever that

previously resulted in a drug injection. The animal does this even if

no drug is given by the lever press (see Figure 2-4). Previous drug use

has conditioned the animal to look for the drug in situations that elicit

cravings in humans.