Aetna Inc. is headed to trial in a class action challenging its refusal to cover transcranial magnetic stimulation, a noninvasive procedure used to treat depression.

At issue in the case is whether Aetna violated federal benefits law by developing and implementing a policy that denied coverage for TMS on the grounds that the treatment was experimental and investigational.

A federal judge in Connecticut Oct. 11 refused to grant early judgment to Aetna, holding that there were disputed issues of fact...