Research into understanding drug cravings

Our medical director, Dr Prun Bijral, contributed to an article in the journal Addiction Biology on understanding the triggers for drug cravings. You can read the full report here.

How observing a salivating dog helped us understand the triggers for drug craving

In the late 1800s the Russian physiologist, Ivan Pavlov made a groundbreaking discovery. Like most key scientific discoveries, it occurred purely by chance. Pavlov was studying the salivary reflex in dogs in response to food. In his experiment, a lab assistant entered the room and put some food down in front of the dogs. Naturally, the dogs salivated. However, Pavlov noticed that after a while, the dogs began to salivate as soon as the lab assistant entered the room before they put the food down, and also when they came in without any food.

This chance observation led to Pavlov’s theory of ‘Classical Conditioning’. It can teach us something about addiction. The brain processes or ‘conditioning mechanisms’ that made the dogs salivate just because the lab assistant just came into the room are the same as those that result in craving responses to things like money, friends and even environments (what we call ‘drug cues’).

According to Classical Conditioning, a previously ‘neutral’ stimulus (like the lab assistant before they ever brought food in the above example, or money before it was ever used to buy drugs) gains the ability to produce a strong emotional/physiological response (salivating in the above example, or craving for drugs), just by being repeatedly associated with something rewarding.

The brain ‘expects’ drug reward after drug cue exposure

The brain learns that these stimuli are often followed by the reward (drugs or food) and so it starts to expect them. This expectation is largely unconscious. The person might not consciously think that a drug reward is coming when they see the cue, but their brain will trigger a range of responses readying the body for drug reward, and craving is one of these.

The aim of our study

Cravings contribute to relapse, so we were interested in understanding exactly what brain processes contribute to the craving response. Identifying the parts of the brain that contribute to craving will help us develop targeted drug therapy or psychological treatment to block or lessen cravings and help maintain abstinence.

How we investigated craving

We used a video of drug cues produced with the help and guidance of staff and service users of the Chapman-Barker Unit (CBU), to trigger drug craving in newly detoxified opioid-dependent participants (with their consent). We also used non-invasive brain imaging technology to look inside their brains. Then we examined the minute-by-minute changes in brain activity that tracked the increase and decrease in craving over time.

What we found

We found activity in the amygdala, a key emotional processing region of the brain, increased and decreased in line with craving. This led us to conclude the amygdala was a key region in creating craving.

Interestingly, we found that activity in the anterior cingulate cortex (ACC) (which has been previously associated with craving), did not fluctuate in line with craving. In fact, it became more active as craving decreased. This led us to conclude that the ACC is involved in limiting cravings.

Next steps

We want to use what we've learnt to test for new treatments that might reduce activity in the amygdala or increase anterior cingulate activity in the hope of finding a treatment that cuts craving to help with abstinence.