Nearly 30 years after chronic fatigue syndrome was given its unfortunate name, it’s still not understood or even completely accepted by the medical world: No definitive cause has been identified, nor any consensus treatment. And while it affects an estimated 1 million Americans and 17 million globally, those with the condition are often dismissed as suffering from psychosomatic disorders.

If nothing else, “Unrest,” by Jennifer Brea, demonstrates just how debilitating chronic fatigue syndrome, also known as myalgic encephalomyelitis, can be. Ms. Brea, herself a victim, was a well-traveled Ph.D. student at Harvard who fell ill after a high fever in 2011. Along with exhaustion, she experienced loss of muscle control, the inability to speak coherently, pain, and extreme sensitivity to light and noise. Specialists at first concluded that she was dehydrated or stressed; one even suggested a delayed reaction to some childhood trauma that she might not recall.

In trying to understand chronic fatigue syndrome, Ms. Brea found other sufferers online and includes some of their stories here — a young Englishwoman bedridden for eight years, a Danish girl kept against her will in a psychiatric hospital for three years. Other interviews lightly sketch the history of the medical response to the syndrome, and how utterly insufficient it seems to be. Research money is only a small fraction, the film says, of that for multiple sclerosis, a condition afflicting roughly half as many Americans.

Mainly, though, “Unrest” is a video diary and, as such, is not always easy to watch. Ms. Brea bravely spares very little in showing how the disease literally leveled her life — at times leaving her crawling the floor — and strained her marriage. The film is also not vested in an upbeat ending. Rather, it powerfully insists on giving a voice to victims whose greatest challenge, apart from their symptoms, is surmounting a world of indifference.