Using marijuana as a teenager does not appear to be linked to health problems such as depression, psychotic symptoms or asthma later in life, a study has revealed.

Researchers found no difference in the mental or physical health of adults who had smoked cannabis as a teenager, and those who had not.

'What we found was a little surprising,' said lead researcher Dr Jordan Bechtold, of the University of Pittsburgh Medical Center.

'There were no differences in any of the mental or physical health outcomes that we measured regardless of the amount or frequency of marijuana used during adolescence.'

Using cannabis as a teenager does not appear to be linked to physical or mental health problems later in life, according to new research (file photo)

As part of the study, the researchers tracked 408 Pittsburgh males from adolescence into their mid-30s.

Around 54 per cent were black, 42 per cent were white and 4 per cent were of other races or ethnicities.

The men in the study were divided into four groups based on their reported use of marijuana.

The groups included low or non-users (46 per cent); early chronic users (22 per cent); participants who only smoked marijuana during adolescence (11 per cent); and those who began using marijuana later in their teen years and continued using the drug (21 per cent).

Based on previous studies, the researchers expected to find a link between teenage marijuana use and the development of psychotic symptoms (for example delusions and hallucinations), cancer, asthma or respiratory problems later, but they found none.

The study also found no link between teenage marijuana use and lifetime depression, anxiety, allergies, headaches or high blood pressure.

There were no differences in the findings based on race or ethnicity.

The paper was one of just a few studies focusing on the long-term health effects of teenage marijuana use, which has tracked hundreds of participants for more than two decades of their lives, Dr Bechtold said.

The study found no link between teenage marijuana use and lifetime depression, anxiety, psychosis, cancer, asthma, respiratory problems, allergies, headaches or high blood pressure (file photo)

Early long-term users of the drug reported much higher use of marijuana, which rapidly increased during their teenage years to a peak of more than 200 days per year on average when they were 22 years old.

Their marijuana use then declined somewhat as they got older, scientists noted.

The researchers accounted for other factors that could have influenced the findings, including cigarette smoking, other illicit drug use, and access to health insurance.

The study was carried out in the US, where a person's level of health insurance affects their access to treatment.

Since the study included only males, there were no findings or conclusions about women.

Relatively few participants had psychotic symptoms, the researchers noted.

'We wanted to help inform the debate about legalisation of marijuana, but it's a very complicated issue and one study should not be taken in isolation,' Dr Bechtold concluded.