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 Cocaine addicts can't recognise loss - such as the consequences of a break-up or being sent to jail - because the drug changes their brain, according to a new study.

Researchers found cocaine addicts may continue their destructive drug habit despite such huge personal setbacks because their brain circuits responsible for predicting emotional loss are impaired.

They say the find could be used to develop new treatments, and spot those most at risk of relapsing. 

New York researchers found cocaine addicts continue their destructive drug habit because their brain circuits responsible for predicting emotional loss are impaired.

The study, published in The Journal of Neuroscience, focuses on the difference between a likely reward, or loss, related to a given behaviour and a person's ability to predict that outcome - a measurement known as Reward Prediction Error, or RPE.

Such RPE signaling is believed to drive learning in humans, which guides future behaviour. After learning from an experience, we can, in the best case, change our behaviour without having to go through it again.

Previous research determined that predictions of actual reward or loss are managed by shifting levels of the nerve signaling chemical dopamine produced by nerve cells in the brain, where changes in dopamine levels accompany unexpected gains and losses.

The new study recorded the brain activity of 75 people - 50 cocaine users and 25 healthy controls - using EEG, a test that detects electrical activity in the brain, while subjects played a gambling game. Each person had to predict whether or not they would win or lose money on each trial.

Results showed that the group of cocaine users had impaired loss prediction signaling, meaning they failed to trigger RPE signals in response to worse-than-expected outcomes compared to the 25 healthy people.

Researchers say their findings offer insights into the compromised ability of addicts to learn from unfavourable outcomes, potentially resulting in continued drug use and relapse, even after suffering major losses.

Study lead author Doctor Muhammad Parvaz, Assistant Professor of Psychiatry at the Icahn School of Medicine in the US, said: 'We found that people who were addicted to cocaine have impaired loss prediction signaling in the brain.

'This study shows that individuals with substance use disorder have difficulty computing the difference between expected versus unexpected outcomes, which is critical for learning and future decision making.

'This impairment might underlie disadvantageous decision making in these individuals.'

The new study recorded the brain activity of 75 people - 50 cocaine users and 25 healthy controls - using EEG, a test that detects electrical activity in the brain, while subjects played a gambling game

The study also looked at differences among the 50 cocaine users. 

Half had used cocaine within 72 hours of the study and the other half had abstained for at least 72 hours. 

The cocaine addicts with the more recent use had higher electrical activity associated with the brain's reward circuit when they had an unpredicted compared to a predicted win, a pattern that was similar to the 25 healthy controls.

The cocaine users who had abstained for at least 72 hours did not show the higher activity in response to an unpredicted win.

The researchers said these findings are consistent with the hypothesis that in addiction the drug is taken to normalise a certain brain function, which in this case is RPE signaling of better-than-expected outcomes.

Principal investigator Doctor Rita Goldstein said: 'This is the first time a study has targeted the prediction of both gains and losses in drug addiction, showing that deficits in prediction error signaling in cocaine addicted individuals are modulated by recent cocaine use.

'The reductions in prediction of loss across all cocaine addicted individuals included in this study are also of great interest; they could become important markers that can be used to predict susceptibility for addiction or relapse or to develop targeted interventions to improve outcome in this devastating, chronically relapsing disorder.'