An investor in the cannabis industry has donated $9 million to Harvard and MIT to study the drug’s health effects, in what the institutions describe as the largest private gift to support marijuana research.

The Broderick Fund for Phytocannabinoid Research, announced Tuesday morning, will be shared equally by Harvard Medical School and the Massachusetts Institute of Technology, with the goal of filling vast gaps in the understanding of how marijuana affects the brain and behavior.

“The lack of basic science research enables people to make claims in a vacuum that are either anecdotal or based on old science,” said the donor, Charles R. “Bob” Broderick, an alumnus of both universities. “For generations we haven’t been able to study this thing for various sorts of societal reasons. That should end now, as well as the prohibitions that are falling around the world.”

Broderick has invested heavily in the booming marijuana business, starting in Canada in 2015 and more recently the United States, through his family-run Uji Capital.

Although Broderick stands to profit if the studies find benefits from marijuana, the universities and the researchers said the donor will have no say in the work process or its results. They also pledged to publish their findings even if they find marijuana doesn’t help or causes harm.

Broderick recalled the first time he raised the idea of funding cannabis research with a Harvard development officer: “There was silence on the other end. Then she said, ‘I don’t think we do it.’ And I said, ‘That’s the problem.’ ”

The official soon called back to say that Harvard researchers studying brain chemicals would be interested in examining marijuana’s effects.