To keep premiums — and expenses — low, health insurance companies rely on what are called “narrow networks” of providers, limiting the consumer’s options. Now the Harvard School of Public Health has found that 15 percent of the 135 silver plans its researchers studied did not include a single in-network specialist for at least one specialty.

Such specialties include endocrinology, rheumatology and psychiatry, among others.

“This translates into huge cost burdens for patients,” said lead author Stephen Dorner. The study was published in the Journal of the American Medical Assn. (JAMA).

The study did not name the plans, or the states they’re offered in, but said the deficient policies cut across the swath of rural and urban dwellers. The researchers studied only plans offered on, which covers 38 states.

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