Brain’s sense of pleasure and reward “blunted” in alcohol addiction

New study shows that a crucial part of the brain’s reward system is “blunted” in alcohol addiction, even after long periods of abstinence.

The findings, published recently in Molecular Psychiatry, demonstrate for the first time how fewer endorphins – chemical messengers in the brain that can trigger feelings of happiness and reward – are released in the brains of individuals with alcohol addiction when compared to a control group. This follows similar results from a previous study by the team of gambling-addicted individuals. 

Researchers used PET (Positron Emission Tomography), a special kind of scan that shows the brain’s chemical messengers at work, to try and better understand how the brain’s endorphin system is changed by alcohol addiction.

Seeking compensation

The brain’s endorphin system plays an important role in our sense of pleasure, pain and reward, and there is growing evidence that an imbalance in this system could underpin addiction. Addiction is sometimes described as a “reward deficient” state, in which individuals are unable to derive happiness or an “endorphin rush” from normally rewarding activities and compensate for this with substance use.

As such, a number of treatments for addiction have been developed that target the brain’s reward system, but these are not always effective. According to recent figures, three quarters of individuals with alcohol dependency will relapse within the first year of receiving treatment.

“A better understanding of the underlying changes in the brain’s reward system associated with alcohol dependence will allow us to develop better treatments,” explains lead author Dr Samuel Turton.

“It will also help us to understand which individuals will most likely benefit from particular treatments.”

Exploring the alcohol dependent brain

To further investigate, the study team recruited a group of 13 abstinent alcohol dependent individuals who underwent two PET scans – one before and one after having received a small dose of dexamphetamine (a medication prescribed in attention deficit disorder) which was used to stimulate a response from the brain’s endorphin system. The team also performed the same tests on a control group of 15 individuals without addiction problems.

Crucially, they found that the alcohol dependent participants released significantly less endorphins than the control group. They also discovered that this reduced release of endorphins did not appear to change even after long periods of abstinence from alcohol.

Notably, this is the first time that lower endorphin release has been shown in alcohol addiction. Given that the findings are similar with those from a previous study in gambling addiction, this suggests that low endorphin release is something common to a number of different types of addiction.

However, the study does not show whether this dysregulation in the brain’s reward system is a direct result of alcohol addiction or is something that is present prior to the development of addiction. It is also still unclear as to whether releasing less endorphins is linked to increased risk of relapsing to alcohol use after treatment.

Next steps

Commenting on the limitations of the study, Dr Turton said: “Further research is required to address some of the key questions that have arisen from this investigation.”

“We need to clarify if lower endorphin release is also present in people who are at a higher risk of developing alcohol or gambling addiction, in order to understand if this might be a pre-existing risk factor.”

“We will also further investigate how changes in the brain’s reward system in addiction  relate to the risk of relapse after treatment, and how this might affect the use of different treatments for addiction.”

‘Blunted endogenous opioid release following an oral dexamphetamine challenge in abstinent alcohol-dependent individuals’ by Samuel Turton et al., is published in Molecular Psychiatry.