Marijuana policies are evolving quickly in the United States, with every state in New England legally permitting marijuana to be used for medicinal purposes. Washington state, Colorado and other states have fully legalized marijuana use for recreational purposes. Voters have passed ballot measures allowing for full legalization and regulation of marijuana sales in Oregon, Alaska and Washington, DC; Massachusetts will likely vote on a similar measure in 2016.
Amidst this sea change, families are increasingly asking providers about the safety and efficacy of marijuana for pediatric and adolescent conditions. Autism, in particular, has received much attention. As pediatricians, we know families who have struggled with autism and recognize that in severe cases, self-harm and violent behaviors can be particularly difficult to control.
It’s not surprising that many families have turned to alternative therapies for autism when conventional therapies have fallen short. Marijuana is one such therapy that has been promoted by some circles. A quick Google search reveals a number of support groups and organizations advocating for the use of marijuana for autism (as well as other developmental and behavioral conditions, such as attention deficit hyperactivity disorder). Perhaps you’ve even been asked about medical marijuana in your own practice.
At this time, no large, high-quality studies have examined marijuana for the treatment of autism or other developmental or behavioral conditions. We recently reviewed the state of the evidence in the Journal of Developmental and Behavioral Pediatrics, finding that, despite a lot of advocacy, at this time the known harms of long-term marijuana administration outweigh any benefits.
Before looking at the known harms, let’s start by considering any theoretical benefits. Some parents anecdotally report that their child’s behavior improves with orally administered marijuana. This may be because marijuana has a sedating effect; whether or not an effect exists above and beyond simple sedation is not yet known.
Additionally, because marijuana contains many different cannabinoids (compounds that act on the body’s endogenous cannabinoid receptors), it is unclear which specific compounds may be helpful in improving behavior. One cannabinoid—cannabidiol (which may have medicinal properties without the psychoactive properties of THC)—recently received a lot of attention for its potential role in treating intractable seizures; however, early studies have not yet shown promise.
…but certainly risks
Whereas potential benefits of marijuana are not yet supported by research, there are decades of carefully conducted research showing potential harms from long-term use. Persistent use was linked to an 8-point decline in IQ in a carefully conducted, decades-long prospective cohort study. A 2007 meta-analysis showed increased odds of psychosis among long-term marijuana users, and a recent large prospective cohort study showed nearly triple the odds of an adult anxiety disorder.
Whether these studies of otherwise healthy marijuana users are generalizable to children with autism is certainly debatable. What’s more, some have argued that reverse causality may be at play. (In other words, predisposition to psychosis or an anxiety disorder causes individuals to use marijuana, perhaps to self-medicate, rather than marijuana causing psychosis or anxiety.)
On the other hand, studies also show how marijuana plausibly causes long-term brain changes. The brain contains abundant cannabinoid receptors—particularly during childhood and adolescent neurodevelopment—that are normally acted on by endogenous cannabinoids such as anandamide. Ingesting or smoking marijuana swamps these receptors with enormous amounts of high-affinity THC and other cannabinoids. THC changes brain structure and function in developing mice, while functional MRI studies have revealed significant, widespread neurological changes in long-term marijuana users compared to non-users.
Is it time? In a word, no
While there is emerging anecdotal evidence among parents that marijuana may be helpful in autism, pediatricians should exercise caution in recommending it at this time. The benefits are not yet established, whereas the potential harms are well described.
Keep in mind that normally, when we recommend a particular medication for a patient, that medication is carefully formulated by a pharmacy and is given in a specific dosage. Medical marijuana, where available, is sold at a dispensary in a tincture or plant form in which neither its contents nor concentrations are known. It is critical that we engage families in careful conversations about medical marijuana and its potential limitations.
Scott Hadland, MD, MPH, is a general pediatrician and graduating adolescent medicine fellow at Boston Children’s Hospital. He recently published a review on marijuana and developmental and pediatric conditions.