How marijuana affects babies to adults

Symposium at UC San Diego goes over latest scientific evidence about medical uses of pot

By Paul Sisson

Researchers are trying to better understand marijuana's influences on a variety of health conditions and its effects on children versus adults. EFE/File

The topic of marijuana got a serious scientific treatment Wednesday at the University of California San Diego, where researchers outlined the latest evidence about the drug. 

The federal government estimates that 22.2 million Americans use cannabis today, an increase of about 4.4 million since 2002. The rise comes amid a growing medical marijuana movement that has culminated with full legalization in Colorado, Alaska, Oregon, Washington state and Washington, D.C. 

California could join those ranks in November if the state’s voters approve marijuana for recreational use.

Science is trying to catch up with the public’s growing acceptance and use of a plant that contains 400 chemical compounds, including more than 60 cannabinoids known to act directly on specialized receptors in the brain.

Understanding just how these compounds work — how they influence issues such as addiction, pain relief and even control of severe childhood seizures — is an evolving effort.

Wednesday’s symposium started with a presentation on marijuana’s prenatal impact.

The speaker was Larry Parsons, a member of the Committee on the Neurobiology of Addictive Behavior at The Scripps Research Institute in La Jolla. Parsons explained that THC, a cannabinoid that gives marijuana its psychotropic effects, clearly affects brain development before birth and can cause lasting effects into adulthood.

Research on mice and observation in humans have shown that THC influences neuron development and signaling, potentially increasing the risk of memory problems, addiction and perhaps schizophrenia later in life.

Also weighing in was Christina Chambers, director of the Center for Life Course Research, part of UC San Diego’s Clinical and Translational Research Institute.

She said studies of children whose mothers used marijuana during pregnancy suggest that the drug elevates the risk of hyperactivity, attention deficit disorder, lack of motor coordination and poor academic achievement during the first two decades or so of life.

However, all of these results came from relatively small studies — and many of those studies are decades old. Larger, newer clinical trials are necessary to prove marijuana’s imprint on childhood development.

“The sample sizes are so small. There is a critical need for more data,” Chambers said.

As it happens, UC San Diego is in the thick of a massive research project that is expected to yield unprecedented insight into how the adolescent mind is affected by marijuana and many other factors.

The university is coordinating the Adolescent Brain Cognitive Development Study, which is tracking 10,000 children across the nation for a decade.

Annual testing, which will include highly sensitive brain imaging, is expected to help researchers map how life events of all kinds shape brain development.

“To be able to study kids longitudinally, starting at age 9 and 10, is going to transform our understanding,” Chambers said.

Adults also got attention during Wednesday’s event.

Researchers said studies indicate that medical marijuana is most effective at fighting muscle spasms caused by multiple sclerosis and at combating the neuropathic pain that cancer patients often suffer.

There is also evidence, though less robust, of cannabis’ effects on nausea caused by chemotherapy, in promoting weight gain for HIV-infected patients and in easing sleep disorders.

On the flip side, cannabis can cause nausea, dizziness, impaired driving, addiction and a reduction in cognition.

Meanwhile, the cognitive effects of marijuana are thought to be less severe in adults than in children and adolescents.

Scientists continue trying to determine the proper dosing for conditions where marijuana shows promise. Sometimes, the right answer can be a bit counter-intuitive.

For example: Dr. Barth Wilsey, an associate physician of psychiatry at UC San Diego, cited research that shows marijuana with a THC concentration of only 1.3 percent is just as effective at controlling neuropathic pain as varieties with more than twice the potency.

“You don’t need a very high concentration to bring about relief,” Wilsey said.

One topic concerning children that did not get much attention Wednesday was the increasing use of low-THC hemp oil to treat epileptic seizures.

Media coverage and social-media stories of sometimes-miraculous decreases in seizure activity for some kids treated with the oil has prompted many states to legalize its use.

But more recent studies have found, again in small numbers of children, that the oil is not a panacea.

Dr. Kevin Chapman, who works in the pediatrics department at Children’s Hospital Colorado, co-authored a 2015 study showing that only a third of 75 kids in his state treated with cannabis oil saw a 50 percent or greater reduction in seizures.

And researchers discovered that 44 percent of the test subjects suffered adverse events, including an increase in seizures for 13 percent of the participants.

This observational study has limited value because it did not control for factors such as the children using different doses and types of hemp oil, Chapman said Wednesday in a phone interview.

He noted that British drug company GW Pharmaceuticals is about to release results of the world’s first double-blind, placebo-controlled study of cannabidiol compounds in children with a rare form of epilepsy.

Seen as the gold standard of medical research, this type of clinical trial should shed brighter light on the question of just how much marijuana might help or hurt kids suffering from seizures, Chapman said.

Until the debate is fully settled in scientific circles, he advised families to use high-cannabidiol hemp oil, often called CBD, as a last resort.