Ontario Mothers' Substance-Related ER Visits More Than Doubled. Other Women's Barely Budged.

Sixteen years ago, women who had given birth and were raising children used less hospital care for substance problems than other women their age. By 2024 they used substantially more — and the reversal happened almost entirely among those under 25.

That is the shape of a population-wide study published Oct. 25 in the Canadian Medical Association Journal by a team from Bruyère Health Research Institute, the Ottawa Hospital Research Institute, ICES and the University of Toronto. The researchers followed 5,025,622 females in Ontario from 2008 to 2024, 46.9 percent of them birthing parents with at least one child under 19, and compared age-standardized rates of substance-related emergency department visits and hospital admissions against a 1:1 age-matched group of other females.

A Crossover, Not a Gap

In 2008, the birthing parents were the lighter users of acute care: 387 emergency visits per 100,000 person-years against 421 for their matched peers, and 99 hospital admissions against 136.

By 2024 the ordering had flipped and the distance had widened. Emergency visits reached 894 per 100,000 among birthing parents while the comparison group climbed to 542. Admissions reached 259 against 209. Modelled as average annual percent change, emergency visits grew 4.8 percent a year in the birthing-parent group versus 1.7 percent in the comparison group; admissions grew 6.0 percent versus 3.3 percent. Both differences were significant at p < 0.001.

The age split is where the finding sharpens. Rates rose faster among birthing parents under 25 than among other females under 25 — but for everyone 25 and older, the two groups moved on nearly parallel tracks. Parenthood alone did not drive the divergence; young parenthood did.

Growth appeared across every substance category the authors examined, concentrated in opioids, amphetamines and cannabis. The authors call for more integrated and responsive services, and for upstream policy that supports family health rather than treating parental substance use as an individual failure. For clinicians, the practical implication is that dual diagnosis care — substance treatment and perinatal mental health under one roof, with childcare that makes attendance possible — is the configuration this data points toward, not a specialty add-on.

What the Design Can and Cannot Say

The study's strength is its size and its denominator: linked provincial administrative records covering essentially the whole population, with a matched comparison built into the design rather than borrowed from another jurisdiction's rates.

Its limits are the limits of administrative data. Substance involvement is identified from diagnostic codes on hospital records, so the trends track documentation practice as well as disease; a coding shift toward recognizing substance involvement would produce part of this curve without any change in underlying use. The "birthing parent" definition requires a recorded birth and a dependent child, which excludes parents whose children are not in the household and women who gave birth outside the province.

There is also a plausible competing explanation the authors do not test: women who have recently delivered are in frequent contact with the health system, and contact is what generates a diagnosis. That could inflate the birthing-parent rate without reflecting heavier use — though it fits the 2008 baseline poorly, when the same contact existed and the rate was lower.

What survives those caveats is the direction and the age concentration. Whatever is being measured, the group raising young children in Ontario is now the group arriving in emergency departments with substance-related diagnoses at nearly twice the rate of its peers, and the trend line has not bent.