Scientists have made a shocking discovery - cocaine is even more addictive than first thought.
The research, published in the medical journal Scientific Reports, suggests that using cocaine even once may lead to addiction.
"The study provides evidence that some of the characteristic brain signals in people who have developed addictions are also present much earlier than most of us would have imagined," said McGill University Professor Marco Leyton, an expert on drug use and addictions.
A NZ wastewater study showed that Cocaine only showed up in water samples at weekends.
Recreational cocaine users were filmed doing the drug in the laboratory with a friend they'd previously used the drug with.
During a follow-up session, the users' brains were scanned while they watched a video of their friend doing cocaine.
The results showed an increase in both craving and dopamine release, and scientists say it shows recreational users may be closer to losing control of their behaviour than they think.
"An accumulation of these brain triggers might bring people closer to the edge than they had realised," said Prof Leyton.