As Maine approaches implementation of the recreational marijuana referendum, controversy continues about possible risks attendant on wider availability.

Many of these have been fiercely debated for years, e.g., whether marijuana use is a “gateway” leading to use of other, more harmful substances. Other concerns have emerged more recently.

Media stories highlighting the poisonings of children in Colorado by ingestion of THC-laced gummy bears have led some municipalities to pre-emptively draft ordinances banning sales of such products. However, if experience with attempting to limit the availability of alcohol to adults is any indication, it’s likely that despite attempts to restrict use by young people, legalization may make THC-containing products more widely available to children and adolescents.

A recent study cited in the Journal of the American Medical Association Pediatrics stated that usage by 8th- and 10th-graders in Washington state has increased (2 percent and 4 percent respectively) following marijuana legalization in 2012, with rates of perceived harmfulness of marijuana dropping by 4 percent and 16 percent in these age groups.

One largely unrecognized risk of heavy daily exposure to THC-containing products in adolescence is the potential of “unmasking” or accelerating the emergence of major mental illness. The experience of researchers in Portland’s Identification and Early Referral program (PIER) and at other “early intervention” sites around the world attempting to prevent or delay the emergence of schizophrenia, bipolar disorder or other psychotic illness confirms this danger for the small number of adolescents at higher risk of developing one of these serious and potentially disabling disorders.

A family history of more serious mental illnesses may be a clue to vulnerability in a young person, but often there is no way to predict which individuals are at greater risk for the emergence of paranoid thinking or disturbances of perception and mood which may evolve, in the worst cases, to become lifelong mental illness.

One young man whose psychotic symptoms, including paranoid delusions and occasional hallucinations, had been controlled with treatment in the PIER program before traveling to Amsterdam, where he smoked large quantities of readily available marijuana.

Despite continuing to take anti-psychotic medication, his former psychotic symptoms re-emerged with greater severity, terrifying him that he would never return to his normal level of mental functioning. Fortunately, after he stopped daily use of marijuana, his psychotic symptoms disappeared.

If greater numbers of young people in Maine use marijuana or THC-containing products daily, whether by smoking or by ingestion, they could essentially become part of a public health experiment in reverse: exposing a large population to a particular risk factor with potentially serious consequences (even for relatively few vulnerable individuals) and waiting to see which unlucky “subjects” get in serious trouble.

This population at risk may be expanding, according to a recent study in Psychiatric Services, a journal of the American Psychiatric Association, that reported data from five large U.S. health care systems over a period from 2007 to 2013. The rate of initial presentation of psychotic symptoms in 15- to 19-year-olds averaged nearly 1 percent each year.

While there are compelling arguments on both sides of the legalization question, awareness of this lesser-known but more serious consequence can lead to earlier detection and referral to specialized intervention. Regrettably, the potential demand for the specialized multidisciplinary early intervention programs, which are the most successful in addressing first episode psychotic illness is already exceeding capacity nationwide, according to Dr. John Kane, chair of the Psychiatry Department at Hofstra School of Medicine.

Maine cannot afford to terminate federal funding earmarked for the PIER program, risking aggravating the existing shortage of badly needed treatment programs for a vulnerable population at a critical time.

This column, which appeared in the March issue of the Maine Medical Association newsletter, was reprinted with permission. For more information about youth risk and marijuana use, contact the MMA at mainemed.com.