I got a call last week from a friend who has been successfully battling cancer. She told me: “Marijuana tea and candy are the only things that helped my appetite. My weight had gone down to 98 pounds. I am now 112 pounds. And it let me sleep. I don’t think that I would be alive today without it.” I am glad my friend found relief.

Marijuana may be useful in alleviating the symptoms of a variety of medical illnesses and syndromes including chronic pain, multiple sclerosis, glaucoma and cancer. It can enhance appetite, induce sleep and be pleasurable. Criminalization of marijuana use has been costly and destructive to society. Nonetheless, it is hard for me to see how making medical marijuana available through the dispensaries that may soon open on Martha’s Vineyard is a safe or wise route for us to follow. Here are my concerns:

There are no long-term studies of the use of medical marijuana and few studies of its therapeutic effect. Medical marijuana’s risks versus its benefits are entirely unclear.

Marijuana is associated with a variety of medical problems including respiratory disease, decreased coordination, decreased ability to learn, decreased short term memory, increased anxiety, paranoia and dependence. One out of 10 users and half of daily users will become addicted. Withdrawal is associated with anxiety, irritability, anger, insomnia and depression. Most of these symptoms are the very reasons why many recreational marijuana users end up pursuing medical marijuana. To what extent is it being prescribed simply to prevent withdrawal? The three most common reasons for the prescription of marijuana are musculoskeletal pain (30 per cent), insomnia (15.5 per cent) and anxiety (13 per cent).

Young people are at particular risk for becoming dependent. I have seen countless people in my practice who started using marijuana as adolescents and went on to become addicted to other drugs, developed chronic psychiatric illnesses and appeared to have plummeting academic and social function related to marijuana use. Does anyone really believe that medical marijuana won’t increase access to people who don’t truly need it for medical reasons? And that it won’t be shared, sometimes with teens and even pre-teens? Beside other risks, marijuana is a gateway drug.

Marijuana use is associated with the onset of chronic psychotic disorders. In a study of 45,000 Swedes over the course of 15 years, individuals who had used marijuana by the age of 18 were six times as likely to develop schizophrenia. An analysis of seven cohort studies revealed a 40 per cent increased risk in those who had used marijuana and a 50 to 200 per cent increase in frequent users. Over the course of my career I have seen many people who developed a new onset primary psychotic disorder. Most of them had developed these symptoms after heavy marijuana use.

I have already seen individuals in my practice who are addicted to opiates and other substances who have obtained prescriptions for medical marijuana. To what extent will medical marijuana legitimize marijuana use for addicts, individuals with psychiatric illnesses, teens and other at-risk populations?

The people who will be prescribing medical marijuana will be physicians who are asked to do little more than take a two-hour online certification course. Who will these doctors be? No doubt some will be experts in treating specific syndromes for which marijuana will be useful. Will the doctors who prescribe really be experts in evaluating addiction risk as well as all of the medical and psychiatric conditions that marijuana can impact? Will they closely follow patients for the risk of side effects?

Will they be responsible for the driving accidents that will occur under the influence, or for the people who will become dependent or for their patients who will develop psychiatric disorders as a result?

Marijuana is a complicated substance which contains over 400 chemicals that contribute to its effects. Content will vary from variety to variety and from dispensary to dispensary. Today’s marijuana has six to 20 times more tetrahydrocanabinol (THC) — the chemical in marijuana most closely associated with its effects — than marijuana in the 1960s. There are medications such as Marinol, which is essentially synthetic THC, which offer much of the medical benefit of marijuana. Why not use purer, safer, standardized, better-studied substances that are dispensed in pharmacies to obtain the same medical benefits?

The way in which marijuana will become available in Massachusetts including on Martha’s Vineyard is a poorly-considered experiment that will have unfortunate consequences in the lives of at-risk individuals, especially the psychiatrically ill, people who struggle with addiction, and teens.

Dr. Charles H. Silberstein is a psychiatrist on the medical staff of the Martha’s Vineyard Hospital. He lives in West Tisbury.