In 2019, Lydia Bugg was working from home when a man tried to break into her house. She fought off the intruder on her porch by hitting him and screaming until he ran away. Shaken by the incident, Ms. Bugg knew what she needed to do next: see a therapist.

“I couldn’t feel comfortable in my house,” she said. “I really didn’t feel comfortable in public.”

A friend told Ms. Bugg that if she didn’t get treated for post-traumatic stress disorder, or PTSD, right away, her symptoms could worsen. But in Nashville, where she lived at the time, no therapist she approached would take her insurance.

Ms. Bugg had Blue Cross Blue Shield, the most popular health care plan in Tennessee. But each therapist told her the same thing: “The way that Blue Cross Blue Shield pays people doesn’t allow us to actually have the time and resources to help you,” Ms. Bugg recalled.

Therapists in private practice have many reasons for not accepting insurance. If they do, they cannot negotiate with the insurance company for a higher wage, ask for a raise or be paid more commensurate with their experience. Despite a federal mental health parity law passed in 2008, insurance plans aren’t actually required to cover mental health treatment.

Undeterred, Ms. Bugg found a cognitive behavioral therapist who specialized in PTSD. The therapist was “hugely helpful,” she said. The therapist’s fee, $170 per session, was not.

“That was a lot of money for me and my husband at the time,” said Ms. Bugg, 35. To make it work, she went to therapy sporadically, going only when she could afford it.