Cannabis is a 'gateway drug' that leads users to harder substances

Cannabis really is a gateway drug that leads users on to harder illegal substances like cocaine by making users more sensitive to its effects

  • Smoking cannabis boosts brains’ sensitivity to cocaine, US researchers report
  • Young rats exposed to cannabis had ‘enhanced reaction’ to cocaine exposure
  • In young humans cannabis abuse can enhance experiences with a different drug 

Cannabis is a gateway drug that gives users a heightened sensitivity to harder illegal substances like cocaine, a new study suggests.

US researchers found adolescent rats that had been pre-exposed to cannabis had an enhanced reaction to their first exposure to cocaine.

Exposure to psychoactive cannabinoids during adolescence was found to ‘prime’ the animal’s prefrontal cortex in the brain. 

If applied to humans, the study suggests smoking a lot of weed as a teenager makes people more sensitive to cocaine and can lead to continued use and addiction. 

Cannabis abuse during adolescence can enhance a person’s initial positive experience with a different drug, such as cocaine, leading to sustained use. 

The findings provide new understanding of how the abuse of cannabis during teenage years may enhance the first experience with cocaine and lead to continued use among vulnerable individuals 

‘This study suggests that teenagers who use cannabis may have a favourable initial reaction to cocaine,’ said study co-senior author Professor Denise Kandel of Columbia University in the US. 

‘[This will] increase their likelihood of engaging in its repeated use so that they eventually become addicted, especially if they carry additional environmental or genetic vulnerabilities.’  

The researchers monitored the brains of adolescent and adult rats after giving them WIN – a synthetic cannabinoid that mimics the psychoactive effects of cannabis – followed by cocaine. 

Analysis found adolescent rats who had already been given cannabis had an enhanced reaction to their first exposure to cocaine.

Cocaine set off unique reactions in the brain’s reward centre, similar to those seen in response to nicotine and alcohol. 

The findings also support the notion that cannabis use as a teenager can enhance a person’s initial positive experience with a different drug – in this case, cocaine.

This in turn can have a serious effect on whether they choose to continue or expand their use of cocaine.  

The results also showed cannabinoids targeted the brain’s prefrontal cortex – the area involved in decision making and self-control.

Exposure to psychoactive cannabinoids during adolescence primes the prefrontal cortex so that it responds differently to cocaine  

It is also one of the last regions of the brain to reach maturity – a fact that has long been linked to high levels of risk-taking behaviour seen in adolescents. 

Abnormal prefrontal cortex activity is also often observed in patients suffering from addiction and stimulating the area can be used as a treatment.

The study provides a new understanding of how cannabis abuse during teenage years can enhance the first experience with cocaine and lead to continued use.       

The authors say the results offer clues to how different classes of drugs reinforce each other in humans by the way of biological mechanisms.

Previous research had revealed key differences in how cannabis and cocaine affect brain chemistry 

‘These and other experiments are key to understanding the molecular changes to the brain that occur during drug use,’ said co-author and Nobel Prize winner Professor Eric Kandel of Columbia University.

‘This knowledge will be crucial for developing effective treatments that curb addiction by targeting the disease’s underlying mechanisms.’ 

Most research involving rodents and addiction has traditionally focused on adult animals. 

It has also largely been limited to studying one substance of abuse at a time, without taking into consideration a history of drug exposure in adolescence.  

‘Our study in rats is the first to map the detailed molecular and epigenetic mechanisms by which cocaine interacts with brains already exposed to cannabinoids, providing much-needed clarity to the biological mechanisms that may increase the risk for drug abuse and addiction, said Eric Kandel. 

The findings were reported in the journal Proceedings of the National Academy of Sciences. 


Cannabis is an illegal Class B drug in the UK, meaning possession could result in a five year prison sentence and those who supply the drug face up to 14 years in jail.

However, the drug is widely used for recreational purposes and can make users feel relaxed and happy. 

But smoking it can also lead to feelings of panic, anxiety or paranoia.

Scientific studies have shown the drug can alleviate depression, anxiety and stress, but heavy use may worsen depression in the long term by reducing the brain’s ability to let go of bad memories.

It can also contribute to mental health problems among people who already have them, or increase users’ risk of psychosis or schizophrenia, according to research.

Marijuana can be prescribed for medical uses in more than half of US states, where it is used to combat anxiety, aggression and sleeping problems. Researchers are also looking into whether it could help people with autism,eczema or psoriasis.

Cannabis oil containing the psychoactive chemical THC, which is illegal in the UK, is claimed to have cancer-fighting properties, and one 52 year-old woman from Coventry says she recovered from terminal bowel and stomach cancer by taking the drug.

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