Marijuana was approved in Maine for medical use in 2009. I am one of a small but growing number of physicians in the state to issue certificates to patients with qualifying conditions.

In my practice, I have witnessed marijuana’s positive effects on a variety of disease states. While cannabis holds an important place in my doctor bag, I am judicious when issuing certificates and seldom jump to recommend it as first-line therapy. Marijuana consists of a class of chemically complex species with enormous therapeutic potential, but people must be educated and receive guidance on its use — something the medical community currently provides.

While I endorse marijuana for medical use, I strongly oppose Question 1. Widespread recreational use will have negative consequences for the welfare of Maine and the health of its citizens. Among the many organizations that share this opinion are the National Alliance on Mental Illness and the Maine Medical Association.

The most flawed argument for legalization is how it would improve public health. The “Yes on 1” Campaign to Regulate Marijuana Like Alcohol declares, “Many Mainers cannot access medical marijuana because they do not have one of the few qualifying conditions or cannot afford a recommendation. Question 1 will expand access to thousands of Mainers who don’t currently qualify.”

I take offense at the idea that thousands would be self-diagnosing and self-medicating. We don’t allow this with prescription medication, so why should cannabis be held to a different standard? Imagine the chaos and catastrophe that would ensue if people could get any medication without a prescription.

Marijuana is not a benign drug. We know that long-term exposure alters brain chemistry and rewires neural pathways. While these changes are beneficial for some, they are dangerous in others. A young man visiting Denver dove off a hotel balcony to his death in 2014 after ingesting a marijuana cookie.

I highlight this incident to reveal a sinister side to cannabis that often escapes public awareness. Numerous studies point to a higher prevalence of psychosis among habitual users. The research also shows that marijuana serves as a catalyst to developing schizophrenia in a vulnerable subset of the population.

Besides deranged thinking, marijuana can cause a myriad of adverse reactions such as palpitations, wheezing, chest pain, vomiting, slurred speech, memory loss and slowed reaction time. A growing number of motor vehicle fatalities have been attributed to pot-impaired drivers. Its chronic inhalation can lead to emphysema or lung cancer. In other words, marijuana has the potential to do real harm.

The obesity rate for Maine now stands at 30 percent, up from 18.9 percent in 2000. As a country we are in the midst of an obesity epidemic. How will that demographic transform if marijuana becomes legal? Experience tells me that it would dramatically worsen.

I have yet to meet someone who became stronger, moved faster or fell a pant size from routine marijuana use. Just the opposite — the science behind cannabinoid receptor activity on appetite stimulation supports this observation. Meanwhile, some epidemiological data suggest that marijuana has a paradoxical effect on weight that is not well understood. The point is, stakes to our health care system couldn’t be higher and we just don’t know.

Another concern is the impact legalized marijuana might have on the illicit prescription drug trade. The majority of those using marijuana for medicinal reasons take it for pain relief. For many in my practice, I have been able to reduce or discontinue narcotics by adding medical marijuana.

In the proposed setting, hundreds of these patients could be treating themselves with marijuana without disclosing it to their physicians, while continuing to receive the same amount of prescription narcotic. Extra pills open the door to diversion.

Marijuana is not a single drug. Each strain contains the active compounds THC and CBD and a symphony of minor ones called “terpenes.” The unique ratio of these compounds is what gives one plant the ability to suppress seizures while another becomes better suited for nausea from chemotherapy.

Selecting the right type and mode of delivery is not a perfect science, but neither is the field of medicine. Without the assistance of professionals, treatment is fraught with pitfalls that stand to undermine the current system.

Peter J. Sacchetti, M.D., has a primary care practice, Independent Health Advantage, in York and is a physician member of the Maine State Board of Licensure in Medicine. The opinions expressed in this column are his own and are not necessarily those of the Maine State Board of Licensure in Medicine, nor does this column represent the board’s official position on Question 1.