New Results on Effects of Cannabis Smoking

A long-term study of nearly 1,000 New Zealanders from birth to age 38 has found that people who smoked marijuana for up to 20 years have more gum disease, but otherwise do not show worse physical health than non-smokers. This research was supported by the Jacobs Foundation and by the New Zealand Health Research Council.

The international research team assessed a dozen measures of physical health, including lung function, systemic inflammation and several measures of metabolic syndrome, including waist circumference, HDL cholesterol, triglycerides, blood pressure, glucose control and body mass index.

These newest study results are part of a longitudinal multi-disciplinary study conducted with the same cohort over a period of more than 30 years. The researchers have looked at cannabis use and its effects on several issues such as mental health, cognitive abilities and economic outcomes and were able to show an increase in psychosis; a cognitive decline; and worse socio-economic situation among those with a long history of cannabis use. “While all our previous studies have shown the negative influence of cannabis, this study on physical health effects of cannabis is the first study that has a positive outcome” said Terrie Moffitt, leading researcher and Klaus J. Jacobs Award Winner in 2010.

Possibility for medical use of marijuana

Study participants who had used marijuana to some degree over the last 20 years showed an increase in periodontal disease from age 26 to 38 but they did not differ from non-users on any of the other physical health measures. To measure cannabis use, the researchers asked study subjects to self-report their use at ages 18, 21, 26, 32 and 38. The cohort in New Zealand is particularly interesting as cannabis is often used exclusively on the island, rather than in combination with tobacco and/or other drugs which is the case in most other western countries.
The study’s statistical analysis found that the decline in periodontal health in pot smokers was not explained by tobacco smoking, alcohol abuse or less tooth brushing and flossing. The lack of physical health problems among cannabis users also was not attributable to them having had better health to begin with or to living healthier lifestyles. Moffitt is pleased with the outcomes of this study as she hopes it might help convince people to use marijuana for medical reasons such as cancer or epilepsy patients.

Mothers and aunties are point of contact

Many of the cohort studies lose participants along the way and heavy cannabis smokers are often among the first to drop out. Moffitt and her team have therefore put a lot of emphasis on making the participants as comfortable as possible to try and keep them aboard. “We offer daycare for those participants with children, so they don’t have to organize a babysitter to come and participate”. The study helps employers to give employees time off to participate in the tests. Those that are in prison get tested in prison. For those living abroad in economically more stable countries like Australia or Canada, the study collaborates with Air New Zealand to fly them back for the tests free of charge. Another important way not to loose participants is to know their whereabouts. “We have a large databank of addresses containing the contact details of participants’ female relatives, as they tend to keep in touch with their mothers or aunts’”, revealed Moffitt.

Research has triggered policy changes

Over the whole period of the longitudinal study some significant findings have also had implications for policy. For example the study has demonstrated how crucial the relationship with the mother is. Children who engaged in light crimes in their adolescents such as shoplifting or breaking into summerhouses who had a warm relationship with their mother, later engaged in a warm relationship with a girlfriend and gave up crime. “The message for judges and police officers is to understand the childhood history of delinquents in order to determine how their career will further evolve”, said Moffitt. If they have had a warm relationship with their mother and did not display violent behavior as children they will most probably not further engage in criminal activities. This research was even used in the United States to change the law so that no teenager can be given a life sentence.
For the future the study will further analyze prominent social, economical and health issues corresponding to the age of the participants such as saving for retirement, becoming religious or infertility. Further tests will also be undertaken in regards to fitness and physical functions such as lung capacity, dental health, quality of blood vessels and thickness of the optical nerve. Stay tuned for more results and insights.