Figure 2. Differential Improvement in Clinician-Rated Depression Severity With Electroconvulsive Therapy (ECT) Based on the North American Adult Reading Test-35 (NAART-35), a Premorbid Intelligence Measure.

Clinician-rated depression severity was measured with the Montgomery-Åsberg Depression Rating Scale (MADRS), a 10-item scale, in which scores range from 0 to 60, with more than 36 indicating very severe depression. The binary outcome for NAART-35 was assigned using a standard score of less than 85 (low average or below), indicating scores that were 1.5 SDs or more below published normative data by the developers of NAART-35, in which scores range from 57 to 113 in the ELEKT-D: Electroconvulsive Therapy (ECT) vs Ketamine in Patients With Treatment Resistant Depression (TRD) trial, with higher scores indicating higher premorbid intelligence. EOT indicates end-of-treatment visit.