How the Irish Helped Shape — and Continue to Shape — the Modern Cannabis Industry

LOS ANGELES -For a small island, the Irish have a remarkable habit of turning up everywhere.  From politics and literature to science and business, the Irish diaspora has left fingerprints across the modern world. Cannabis history is no exception.

Some of the most important figures in the evolution of Cannabis — from early medical research to modern legalization and pharmaceutical development — have been Irish or of Irish descent.

The story begins with William Brooke O’Shaughnessy, the Limerick-born physician who helped introduce Cannabis to Western medicine in the 1830s. Like many Irish of his era, O’Shaughnessy left home and made his mark abroad. Working in India with the British East India Company, he studied Cannabis scientifically and documented its medical use for seizures, pain, and muscle spasms. His work helped move Cannabis from folklore into formal pharmacology and ultimately into Western medicine.

Contemporary portrait of William O’Shaughnessy

A century later, Irish defiance showed up again in the figure of Mary Rathbun, better known as Brownie Mary. Rathbun became a central figure in San Francisco’s medical Cannabis movement during the AIDS crisis. Arrested multiple times for baking Cannabis brownies for sick patients, she refused to stop. When authorities threatened jail, her response was simple: she would go to jail as many times as necessary, but she would not stop helping the people who needed relief.

(Image and main image: Brownie Mary)

Then there is Terence McKenna, whose Irish ancestry ran through his father’s side of the family. McKenna brought something different: intellectual horsepower. A gifted speaker and thinker, he helped expand the cultural conversation around plant medicines and psychoactive plants, including Cannabis.

(Image: Terence McKenna)

In the modern commercial era, Brendan Kennedy helped bring Cannabis into global capital markets as co-founder of Tilray.

Another modern industry figure is Patrick Moher, who served as president of The Green Organic Dutchman during the formative years of Canada’s federally legal Cannabis market.

The Irish presence is also visible in Europe’s emerging medical Cannabis sector. Leah Fletcher, founder of Dunbar Pharma, represents a new generation of Irish entrepreneurs helping build regulated Cannabis businesses across European markets.

And then there is Former Congressman Patrick J. Kennedy, whose famous Irish-American political family has long shaped American public life. Through The Kennedy Forum, Kennedy has influenced the broader conversation around addiction, mental health, and Cannabis research policy.

Ireland’s influence also extends into the pharmaceutical side of Cannabis. Not many people realize that by far the most successful and largest company involved in Cannabis medicines today is Irish: Jazz Pharmaceuticals, headquartered in Dublin and employing thousands of Irish professionals from the C-suite to the laboratories.

(Image: The Lobby of Jazz Pharmaceuticals in Ireland)

Taken together, these stories reflect familiar Irish traits — curiosity, stubbornness, global ambition, intellectual drive, and loyalty to community.

From a Limerick doctor working in India in the 1830s, to a defiant grandmother baking brownies for AIDS patients in San Francisco, to modern executives and entrepreneurs building companies across North America and Europe, the Irish have been quietly present at many key moments in Cannabis history.

And these examples are only a glimpse.

Today there are hundreds of people who are Irish or of Irish descent active across the global Cannabis industry — across North America and increasingly across Europe’s rapidly emerging medical Cannabis markets, with multiple senior managers of German Cannabis companies being Irish.

For St. Patrick’s Day, that is worth remembering.

The Irish imprint on Cannabis is real.

About the author: Mark Collins is a third-generation American of Irish descent and the founder of Highly Capitalized Network (HCN), a business and financial news platform covering the global Cannabis industry. Based in California, Collins writes about the intersection of Cannabis, business, finance, and public policy, and regularly interviews leaders shaping the future of the industry.