MODESTO, Calif. — Topamax. Depakote. Phenobarbital. The list goes on. Before Jayden David turned 5, he had tried a dozen powerful medications to tame a rare form of epilepsy. The side effects were devastating.

There were grand mal seizures that lasted more than an hour. Hundreds of times a day, muscle twitches contorted his impish face.

“If he wasn’t sleeping, he was seizing,” said Jayden’s father, Jason David.

Feeling helpless, David said, he contemplated suicide. He prayed. Then one day he heard about a teenager who was expelled from school for using marijuana to help control seizures.

So began the pair’s journey into California’s medical cannabis culture.

In the 14 months since, the little boy has been swallowing droppers full of a solution made mostly of cannabidiol, or CBD, the second most prominent of marijuana’s 100 or so cannabinoids. Unlike the dominant THC, cannabidiol is not psychoactive, so the sweet-tasting infusion Jayden takes four times a day doesn’t make him high.

Down from 22 prescription pills per day to four, he now eats solid food, responds to his father’s incessant requests for kisses and dances in his Modesto living room to the “Yo Gabba Gabba!” theme song. The frequency and intensity of his seizures have been greatly reduced.

But this summer, federal prosecutors moved to close Oakland’s Harborside Health Center — the nation’s largest dispensary and the place David has relied on most for help.

The public debate over medical marijuana — which violates federal law but is legal in California, 17 other states and the District of Columbia — for the most part has pitted those who praise its health benefits against those who say it is merely an excuse to get high. Lost in the discussion has been the fact that marijuana has myriad components that affect the body in a number of ways.