A risky joint


A medical journal study, published this month, is the first to suggest a specific men’s health risk from cannabis use, reports MICHAEL KELLY

DEPENDING ON who you talk to, cannabis is either a highly addictive and dangerous gateway drug or a benign natural herb that may well have medicinal properties.

Type the words “cannabis” and “myths” into your search engine and you will find websites dedicated to debunking and proving the most common assertions about the drug.

Cannabis is the most widely used illegal drug in Ireland, according to the National Advisory Committee on Drugs. About 17 per cent (almost one in five) of those aged between 15-64 have used the drug in their lifetime with one in 33 of the population described as current users.

There is a degree of public tolerance of cannabis use which does not exist for other illegal drugs – more than two-thirds of those surveyed by the committee, for example, agreed that cannabis should be permitted for medical reasons.

A research study published earlier this month in the journal Cancer is the first to propose a specific men’s health risk from cannabis use.

The study was done by the Hutchinson Cancer Research Center in Seattle and suggests a link between frequent or long-term cannabis use and an increased risk of testicular cancer.

According to the lead researcher on the project, Dr Stephen Schwartz, the results are significant since they highlight a link between cannabis use and an increased risk of the most aggressive form of testicular cancer, non-seminoma, which tends to strike men at a young age (20-35 years).

The researchers discussed cannabis use with more than 350 men aged 18-44 who had been diagnosed with testicular cancer and found that being a cannabis smoker at the time of diagnosis was associated with a 70 per cent increased risk of developing the disease, even after allowing for other lifestyle factors (such as smoking and alcohol consumption) that could also have an impact.

The risk was heightened (about twice that of non-users) for those who used cannabis at least weekly or had long-term exposure to the drug beginning in adolescence.

“Our study is not the first to suggest that some aspect of a man’s lifestyle or environment is a risk factor for testicular cancer, but it is the first that has looked at marijuana use,” says Schwartz.

Although it is still quite a rare condition, the number of men who develop testicular cancer has been steadily increasing. According to National Cancer Registry figures, 162 cases of testicular cancer were reported in Ireland in 2005, up from 69 cases in 1994. This broadly reflects increases in other countries.

“Part of the reason for the increase is that we have increased awareness of testicular cancer among men,” says Dr Thomas Lynch, consultant urologist at St James’s Hospital in Dublin and a regular contributor to Healthplus. “It is also related to population. Testicular cancer tends to occur in a certain age group and we have more people in that age group at the moment.”

According to the Irish Cancer Society, there are a number of known risk factors associated with testicular cancer. It is more common in men with an undescended testicle or who have a testicle that did not descend until some time after birth.

There are also slightly elevated risks if you have had testicular cancer in the past or if you have a family history of the disease.

The disease is thought to originate in the womb when some male cells fail to develop properly and become vulnerable to cancer.

It is thought that exposure to male sex hormones during adolescence and early adulthood encourages the cells to become cancerous which explains why the disease primarily develops at this age.

Researchers at Hutchinson believe that puberty is a “window of opportunity” during which lifestyle or environmental factors can have an impact on the risk of testicular cancer. According to Schwartz, chronic cannabis exposure has multiple effects on the reproductive system, causing decreased sperm quality and testosterone levels.

Because male infertility has been linked to an increased risk of testicular cancer, this further reinforces the researchers’ hypothesis that cannabis use may be a risk factor for the disease.

In addition, the researchers suggest a link between the increase in the incidence of testicular cancer globally and the increase in cannabis use.

“I would consider that a highly spurious connection,” says Lynch. “This is an interesting study but you would need to see the results validated with a much larger sample group and a lot more evidence for the cause-effect relationship.”

According to researchers, that cause-effect relationship could be the result of the fact that the testicles are one of only a small number of areas in the body that have receptors for the main active chemical in cannabis, tetrahydrocannabinol (THC).

The authors also speculate that cannabis may disrupt the effects of an anti-cancer chemical which the male reproductive system produces and that this may also contribute to the occurrence of testicular cancer.

If THC is indeed associated with testicular cancer, there is worrying reading in a 2003 University of Mississippi study which found that the THC potency levels of modern cannabis are increasing (from 1 per cent in the mid-1970s to more than 6 per cent in 2002, and up to an alarming 33 per cent in some samples).

In the absence of further research on the matter, Schwartz cautions young men against smoking the drug.

“What young men should know is that, first, we know very little about the long-term health consequences of marijuana smoking,” he says.

“Second, our study provides some evidence that testicular cancer could be one adverse consequence. So, in the absence of more certain information, a decision to smoke marijuana recreationally means that one is taking a chance on one’s future health.”

It is important to note that the majority of testicular cancers are curable.

“Men are presenting earlier to their doctors and there is far more awareness out there now,” says Lynch.

“The treatments available to us are also far better than they were. Men should do testicular self-examination on a regular basis and if they notice any changes, should report to their doctor immediately. The vast majority of lumps are not cancerous.”


If you are worried about testicular cancer, call the National Cancer Helpline on 1800 200 700 or see www.cancer.ie