Researchers say exposing pregnant mice to marijuana appears to have affected the retinas of newly born mice.

A recent study finds that exposure to marijuana in the womb may affect the development of the offspring’s eye.

These changes were found to persist as mice in this particular experiment aged.

Cannabis is the most commonly used illicit drug across the United States. In 2015, an estimated 11 million people between the ages of 18 and 25 used the drug.

The recent changes in legislation surrounding cannabis have spawned a raft of research investigating its potential health benefits.

Already, medical marijuana can be prescribed to treat a range of conditions and symptoms, including muscle spasms, nausea from chemotherapy, seizure disorders, and Crohn’s disease.

Scientists are also investigating it as a potential treatment for chronic neuropathic pain and the spasticity associated with multiple sclerosis. Cannabis’ ability to prevent cell death in the brain has also been a topic of discussion.

However, because of the increase in usage for recreation and medical purposes, understanding the negative health consequences of cannabis is also important.

Marijuana has a long history of medicinal use.

For instance, it is thought that cannabis was sometimes used as a medicine during the reign of Chinese Emperor Fu Hsi (in 2900 B.C.).

More than 3,000 years ago, Egyptians prescribed cannabis for glaucoma and inflammation as well as for “cooling the uterus.”

Despite this long history, there is still much to learn about how the drug affects people in the long term.

Read more: Do medical marijuana laws encourage adults to misuse the drug?

In particular, the impact of marijuana exposure during pregnancy is relatively understudied.

There has been a dearth of studies examining this aspect and the limited results that have been generated.

One study found that prenatal marijuana exposure did have a negative impact on a child’s intellectual development at the age of 6.

Another found lasting effects of prenatal cannabis smoking on children through to the age of 16, with the authors having measured deficits in problem-solving and other thinking skills.

However, it is important to note that to date, studies looking at these effects have been small-scale and results have been contradictory.

Projects of this type are heavily influenced by a range of other factors that are difficult to control, such as behavioral and social parameters.

The results of the latest study into the potential negative impact of smoking marijuana during pregnancy are being presented at the 2017 Annual Meeting of the Association for Research in Vision and Ophthalmology in Maryland.

Read more: Opioids vs. marijuana: Which is more dangerous?

Specifically, the researchers of the recent study were interested in observing how smoking marijuana during pregnancy might affect the visual system of the developing embryo.

The scientists exposed pregnant mice to either marijuana or filtered air throughout their gestation.

The doses of marijuana were calculated to be equivalent to an average level of human exposure. Following birth, the mice pups were evaluated at the 3, 6, and 12-month marks.

When their eyes were inspected, the mice whose mothers had been exposed to marijuana had significantly thinner retinas than those exposed to filtered air.

As the mice developed, the retina’s thickness did not achieve normal levels by the time the mice reached 1 year old.

Read more: Is the acceptance of marijuana reaching a tipping point?

Little is known about cannabis and its impact on retinal development, so this study is likely to pave the way for more in-depth research.

It raises more questions that will need to be answered.

For example, the current study did not demonstrate what impact these changes to the retina might have on animals as they grow older.

It will also be important to understand whether or not the results are transferable to humans.

If the findings are confirmed, it will help to guide public information and legislation around smoking marijuana during pregnancy.