Users are also more likely to be lower paid and have relationship issues

Another study found heavy use of drug has long term affects on the brain

Experts say cannabis use is linked to poor mental and physical health

Research found that teens who used marijuana heavily were 40 per cent more likely to die by age 60 than those who never used the drug

Study analyzed 45,000 men from 1969 to 2011; 4,000 died during that time

Smoking marijuana heavily during teenage years may lead to an early death, a new study has revealed.

The study analyzed more than 45,000 men who underwent mandatory military training in Sweden between 1969 and 1970.

Scientists from the Karolinska Institutet in Stockholm followed them on the National Cause of Death Register until 2011. During the 42-year study, around 4,000 of the men died.

Research published by the American Journal of Psychiatry found that the men who used marijuana heavily in their late teens were 40 per cent more likely to die by the age of 60 than those who never used it. Heavy use was defined as teens who used marijuana more than 50 times.

Smoking marijuana heavily during teenage years may lead to an early death, a study has revealed (file photo)

It also found that the risk of death from suicide or an accident was directly proportional to the level of marijuana use the men had as teens.

Addiction expert Scott Krakower told CBS News that cannabis users generally had poorer health, and other studies had found early heavy marijuana use was linked with lung cancer and heart problems.

'Marijuana users generally may have poorer diets and they might be tobacco smokers. There's an increased linkage between weed and tobacco,' said Krakower.

Dr. Kevin Hill, a member of the American Psychiatric Association's Council on Addiction Psychiatry, told the network: 'One of the key messages from a study like this comes down to two words: dose matters.'

Hill said that heavy use of marijuana at a young age was linked to poor psychological health and cognitive problems - which may in turn lead to poor food and health choices.

'One 2012 study showed early, regular use of marijuana - the kind of level they describe in this study - led to an eight-point decline in IQ over time,' he said.

'If you start using marijuana at an early age, you're more likely to express a psychotic disorder.'

Another study found that heavy cannabis use has long-term effects on a person’s brain – especially if they start using the drug earlier in life.

Starting to use marijuana before the age of 16 has been found to result in an underdeveloped prefrontal cortex, scientists revealed. That’s the part of the brain responsible for judgment, reason and complex thinking.

In contrast, people who start to use marijuana after the age of 16 experience accelerated brain aging.

Lead study author Dr Francesca Filbey, of the University of Texas at Dallas, said: ‘Not only did age of use impact the brain changes but the amount of cannabis used also influenced the extent of altered brain maturation.’

Through MRI scans, the scientists determined that the more marijuana consumed by early onset users, the greater their cortical thickness. Additionally, early onset users were also found to have less gray and white matter contrast, and a less intricate gyrification.

Research, published by the American Journal of Psychiatry, found that men who used the drug heavily in their late teens were 40 per cent more likely to die by the age of 60 than those who never used cannabis

The scientists said these findings indicate that when the participants began using marijuana before age 16, their brain experienced arrested development in the prefrontal cortex.

International research has also revealed that the more cannabis you smoke, the more likely you are to be lower paid and have relationship difficulties.

The study followed children from birth up to the age of 38 and found people who smoked cannabis four or more days a week over many years ended up in a lower social class than their parents.

It also found that regular and persistent users ended up with lower-paying, less skilled and less prestigious jobs than those who were not regular cannabis smokers.

Financial, work-related and relationship difficulties were further experienced by those taking the drug, which worsened as the number of years of regular cannabis use progressed.

The study, conducted by a team of researchers led by Magdalena Cerda at the University of California and Avshalom Caspi and Terrie Moffitt at Duke University, appeared in the journal Clinical Psychological Science.

'Our research does not support arguments for or against cannabis legalization,' said Cerda. 'But it does show that cannabis was not safe for the long-term users tracked in our study.

'Our study found that regular cannabis users experienced downward social mobility and more financial problems such as troubles with debt and cash flow than those who did not report such persistent use.

'Regular long-term users also had more antisocial behaviors at work, such as stealing money or lying to get a job, and experienced more relationship problems, such as intimate partner violence and controlling abuse.'

Researchers claimed the study was important as it addresses an array of 'potentially confounding factors' not included in past studies assessing cannabis' long-term effects on users.

Economic and social problems persisted in long-term, regular users of pot even after the authors accounted for other potential differences between regular cannabis users and other participants.