One of the state’s most vocal opponents of legalizing recreational marijuana in recent years has been Dr. Deepak D’Souza, a research scientist and professor of psychiatry at the Yale School of Medicine.
In testimony before the legislature and in his role as a member of the state medical marijuana program’s board of physicians, an advisory group for lawmakers, D’Souza has laid out what he says are the dangers of legalization. His four areas of concern are the impact on young people and the developing brain; the anticipated increase in cannabis use disorder; the negative impact on people with serious mental illness; and increased motor vehicle accidents.
But D’Souza, who is also director of the neurobiological studies unit for the Veterans Administration Connecticut Healthcare System, thinks the commercialization of cannabis may pose the biggest threat, fearing that the pursuit of revenue above all else will negatively affect both children and adults. “Commercialization comes at a cost, as we have seen with tobacco and alcohol over the last century,” says D’Souza, who has studied the effect of drugs such as marijuana on the brain since the 1970s.
“The true impact of legalization — commercialization — will only become apparent years from now like it did with tobacco,” he says.
In the meantime, we asked D’Souza about his years of research and what we might expect in the aftermath of legalization. Responses have been edited for length and clarity.
Is marijuana addictive? If so, how prevalent is it and what are the symptoms?
Unfortunately, there is a misconception that marijuana is not addictive or that people cannot become addicted to marijuana. There is no question that marijuana is addictive. There is a common definition of addiction that can be applied to a range of addictive substances. Criteria include: the substance is often taken in larger amounts over a longer period than was intended; a great deal of time is spent in activities necessary to obtain the substance, use it or recover from its effects; craving or a strong desire or urge to use the substance; recurrent substance use resulting in failure to fulfill obligations at work, school or home; tolerance, as defined by either a need for markedly increased amounts of the substance to achieve intoxication and desired effect, or a markedly diminished effect with continued use of the same amount.
How does cannabis affect the developing brain? Is limiting use to ages 21 and older the right approach?
Acutely, cannabis impairs cognitive processes that are essential to learning and the demands of student life such as attention, memory, processing speed, etc. Regular marijuana use may also have long-lasting effects on these cognitive processes, that may or may not recover with abstinence.
Brain development — particularly the prefrontal cortex, which is involved in decision making — continues into the early to mid-20s. The brain’s own endocannabinoid system [a neurotransmitter system that affects mood, memory, motor control, appetite, sleep and more] is involved in brain development, and therefore, disturbance of the endocannabinoid system by exposure to cannabis can alter brain development. There is a suggestion, which warrants further research, that some of these changes may not be reversible.
There is accumulating evidence that exposure to cannabis in adolescence may be associated with several impairments, including mental health problems such as schizophrenia, depression, anxiety, anger, irritability, moodiness and risk of suicide.
In a study published recently by my colleagues, just 1-2 instances of cannabis use in adolescence was associated with structural brain and cognitive effects in adolescents. The study did not show whether the changes were permanent or reversible.
The young brain is more vulnerable to addiction. (Not all exposed to cannabis manifest these problems. Research needs to focus on identifying the reasons why some are more vulnerable than others.)
Thus, setting a minimum age is a good idea. However, it would be prudent to set the minimum age to 25 years instead of 21 years.
There have been conflicting studies about whether teen use of marijuana increases in states that have legalized recreational marijuana. How will teens be impacted by legalization?
Indeed, there are some studies suggesting an increase, while others suggest a decrease in use. Perhaps it might be a bit early to tell. But let’s use some common sense here. Do we really expect that with legalization should come a decrease or no change in teen cannabis use? Even if there are restrictions on the sale of cannabis products to people below the age of 21, has that really worked for either alcohol or tobacco? Most recently we have seen that with vaping. Even though it is forbidden to sell the product to children, there has been a concerning increase in nicotine vaping among children. So, I would predict an increase in the consumption of cannabis by teens.
Do you believe medical marijuana is beneficial for people with certain health conditions?
My position has always been that we make changes to public health policy — such as medical marijuana — based on the highest-quality scientific evidence. For several decades we have agreed in the medical field that data derived from randomized, double-blind, placebo-controlled studies represents the gold standard of evidence. This has served us well in separating remedies that are supported by evidence from those that don’t have supporting scientific evidence. There is some evidence supporting the therapeutic effects of marijuana in a very small number of conditions. Another way of stating this is that there is actually very little scientific evidence supporting the therapeutic effects of marijuana for most of the conditions that it has been “approved” for. In far too many cases, the cart — approval — is before the horse — the available evidence.
For those with medical needs, isn’t marijuana preferable and less dangerous than opioids?
Without question, marijuana has a better safety profile than opioids. Ibuprofen is also safer than opioids. But there is little evidence that marijuana is a substitute for opioids in treating pain. In order to recommend a medication for a particular condition, it should have efficacy in treating that condition and be safe. Merely being safer is insufficient. For each condition, we need to study the efficacy of marijuana before claiming that it is a safe substitute for opioids. If such studies provide clear evidence that marijuana can be used as a safe substitute for opioids in the treatment of pain, then that would be a welcome addition to our resources in fighting the opioid crisis.
What are your thoughts on the issue of drugged driving and effective testing of impairment?
Experiments testing the effects of cannabis on basic skills — attention, for example — used in driving, studies testing cannabis effects on car-driving simulators, and field studies exploring the degree to which cannabis use is responsible for car crashes all provide complementary evidence that cannabis impairs driving. Also, cannabis use is associated with higher rates of motor vehicle accidents and mortality. Law enforcement does not have the tools as yet to test people for cannabis intoxication in the field and we do not have an objective biological roadside test equivalent to a breathalyzer to document intoxication.
What about effects on those with mental illness?
As a psychiatrist, I have been treating people with serious mental illness for 25 years. I have concerns about the impact of legalization on my patients with serious mental illness. Cannabis use predicts adverse outcomes, including higher relapse rates, longer hospital admissions, and more severe psychotic symptoms in people with schizophrenia. Common sense would suggest that with legalization, individuals with serious mental illness would likewise have greater access to cannabis, and we should expect negative consequences.