New US research suggests that exposing children to a combination of secondhand tobacco and marijuana smoke could increase their risk of otitis media (an infection in the middle ear that causes inflammation and a buildup of fluid behind the eardrum) and increase the number of visits to the emergency department (ED).

Carried out by Dr. Adam Johnson at Wake Forest University Baptist Health and Dr. Rakesh D.Mistry at the University of Colorado, the study set out to assess if there was a link between secondhand smoke from marijuana and the number of ED visits among children, as well as the rates of tobacco sensitive conditions including asthma, otitis media and viral respiratory infections.

Researchers surveyed 1,500 caregivers on their tobacco and marijuana use and looked at their children's medical history, including the number of ED visits and the number of tobacco sensitive conditions experienced in the past year.

Caregivers were classified into four categories: marijuana use only, tobacco use only, both tobacco and marijuana use, and neither marijuana nor tobacco use — who acted as a control group.

The researchers found that the children of participants in the marijuana and tobacco group had a significantly higher rate of ED visits compared to the control group and those exposed to only marijuana smoke or only tobacco smoke, however press materials did not specify what the visits were for.

Children of caregivers in the marijuana and tobacco group also had a statistically significant increase in the number of otitis media episodes compared to children in the other groups.

However, the team didn't find any increased risk for the other tobacco sensitive conditions included in the study.

The study is one of the first to show that secondhand marijuana smoke exposure could have an impact on children's health.

However, with many countries and US states now looking at legalizing marijuana in one form or another, whether medically or recreationally, the number of studies looking at the potential health risks and benefits of the drug is growing.

Although there is research to suggest that marijuana may bring health benefits for some adults, especially for those with conditions such as multiple sclerosis, there is a growing body of research that suggests that the drug may have a negative impact if consumed during childhood and adolescence, a time when the brain is still developing.

The results were presented on May 5 at the Pediatric Academic Societies (PAS) 2018 Meeting.