Integrated estimate

Summing the six core categories (after removing the civic volunteerism component as described above) generates a gross cost of $3.48 billion to $8.38 billion.

A portion of these cost streams overlap — the same child who experiences cyberbullying-related health system utilization may also have some portion of that utilization captured in the self-harm category, and the same mental health deterioration may manifest across more than one clinical pathway.

How this factor is set has a significant impact on the overall results. CIHI's Discharge Abstract Database data on multi-morbidity in youth mental health admissions1 shows that 40–55 percent of youth admitted for a primary mental health disorder carry at least one secondary mental health diagnosis. This provides the appropriate empirical anchor for our overlap discount.

However, applying the full 40–55 percent discount to this paper's gross total would overstate the overlap for two reasons. First, the cyberbullying sub-component has already been explicitly deduplicated at the sub-component level: ED visits attributable to cyberbullying are removed from the self-harm hospitalization count wherever they are captured. Treating cyberbullying as having already been cleaned of its primary overlap risk, we apply the CIHI-anchored overlap discount only to the remaining five categories. Second, several cost streams in this analysis — including justice system expenditures, educational disruption costs, gambling financial losses, and productivity losses — do not appear in CIHI mental health inpatient data at all. The CIHI multi-morbidity rate measures co-occurring diagnoses in the same admitted patient; it does not address whether economically distinct cost streams double-count the same underlying harm.

On this basis, we apply a 45 percent overlap discount to the gross total net of the cyberbullying component, consistent with the mid-point of the CIHI 40–55 percent range as applied to the clinical streams. This produces an effective overall discount of approximately 42 to 43 percent — closely aligned with CIHI's lower multi-morbidity bound — and a net annual cost estimate of approximately $2.0 billion to $4.8 billion. The reader can apply their own judgement using the sensitivity table below.

Note: Cyberbullying sub-component treated as pre-deduplicated and excluded from the overlap discount base. Discount rates shown apply to the remaining five categories, consistent with CIHI's 40–55% multi-morbidity benchmark for inpatient mental health admissions.

Across the full range of sensitivities, the annual cost of online harms to Canadian children and youth ranges from approximately $1.7 billion to $6.0 billion. Under the central-case 45 percent discount, the estimate is approximately $2.0 billion to $4.8 billion. Even at the most conservative 55 percent scenario, the annual cost remains approximately $1.7 billion to $3.9 billion.