4 May 2015

Crack addicts hooked on their environment

In the latest in our Lab Talk series, we ask Jee Hyun Kim to describe her research and why it matters.

Around half of drug addicts relapse within a year of going “clean”. My research suggests we’d lower that figure if our crack clinics bore more of a resemblance to a drug den. 

Addicts don’t only get addicted to the “high” of a drug. They also form strong emotional associations between the high and the place where they shoot up. 

Vials of crack, a cocaine derivative. Research has found that where drugs are consumed forms an important part of the pattern of addiction.Credit: GETTY IMAGES

When it comes to stopping the cravings, we need to factor this in. No matter how long an addict has been clean, placing them back in the drug-taking environment can be enough to trigger relapse. We showed this in rats.  

We mimicked the crackhead lifestyle by popping them in a “drug den” fitted with a lever. When the rat pressed the lever, it received a cocaine “reward” and learnt that the action of pressing the lever kept the cocaine flowing. This happened for 12 days. 

Over the next nine days we helped the rats get “clean”. One group spent half an hour each day in the drug den – except that no matter how many times they pressed the lever they didn’t get any cocaine. Eventually they stopped pressing it.

A second group of rats also spent time in the den but without the lever. Even if they wanted to press the lever, they had no choice but to sit in the drug den. 

A third rested in their home cages. 

Then we let all three groups relapse by giving them a little cocaine before placing them back into the drug den with the lever. We measured if they’d broken the habit  by counting the number of times they pressed the lever. 

Not surprisingly, the first group – who’d broken the connection between the lever and cocaine – didn’t bother pressing the lever much. But the second group – who spent time in a drug-free den with no lever – were just as clean.  The group who stayed home fared the worst – they pressed the lever even more than during their cocaine-addicted days. 

So the key to cleaning up the rats was to replicate the drug-user’s environment without the reward – so extinguishing the pleasurable link and reducing cravings triggered by that environment. 

The last thing any drug abuser should do is stay at home,hoping their cravings will go away.  

Paper: Extinction of a cocaine-taking context that protects against drug-primed reinstatement is dependent on the metabotropic glutamate 5 receptor. Addiction Biology, 2015, 20:482-489

Jee Hyun Kim is a neuroscientist at the Florey Institute of Neuroscience and Mental Health in Melbourne, Australia