Health Canada tapped the opinions of children as young as five years old as it attempted to decide what warning symbol would work best in mandatory labelling of cannabis products when pot is legalized later this year.

The purpose of the symbol is to "prevent accidental ingestion of products containing cannabis, in particular by children and youth," the January report to the department noted.

Earnscliffe Strategy Group won a contract worth nearly $60,000 to do focus group testing in three locations — Toronto, Vancouver and Quebec City.

The consultants interviewed children between the ages of five and nine, spoke with 10- to 12-year-olds and did focus groups with teens and adults.

The top choice of those surveyed was described as "attention-grabbing" and "foreboding" by focus group participants of all ages, according to the newly posted report.

This example of suggested cannabis packaging unveiled by Health Canada in March includes the red "stop-sign" warning recommended by focus group participants. (Health Canada)

The report noted its "triple-layered message" — a recognizable stop-sign shape, with a white cannabis leaf on a red background, and the letters THC in white on black.

The use of the THC acronym was viewed as a "conversation-starter" for kids to ask their parents questions about cannabis.

7 symbols presented as options

Seven symbols in total were developed by the government and presented as options, as well as size and colour variations.

Among the research findings:

• Symbols with circular and triangular shapes did not imply any particular meaning, especially among young children.
• That wasn't a problem with the octagon, which "was referred to as a stop sign, inferring meaning to all participants immediately."
• The red background "conveyed a sense of warning, caution and danger." A yellow background had less impact, especially among younger children.

And size didn't matter — at least, not much.

For the participants, their interpretation of the symbols didn't change much with larger versions, although — not surprisingly — they were easier to see.

Proposals made public in March

In March, the Trudeau government rolled out its proposals for how recreational cannabis would be packaged and regulated.

That included mandatory warning labels and a prohibition on packaging designed to appeal to young people.

"We have heard loud and clear from provinces and territories and also from stakeholders that they need to have this information regarding packaging as soon as possible," Health Minister Ginette Petitpas Taylor said March 19.

"So we are very comfortable with the information that has been brought forward with respect to the specifics of the labelling and the packaging and the warning sign that is going to be on all cannabis types of products."