Across the four research sites— UNM, UMinn, MGH and UIowa —188 patients with schizophrenia and 190 demographic, age and sex- matched healthy control subjects were recruited for this study between July 2004 and July 2006 (Table 1). To protect subject identity, testing sites are referred to by letter in this manuscript and online. The final cohort for whom data are available includes 162 patients and 169 controls with site distribution as follows; site A 46 patients/44 controls; site B 44/73; site C 33/27; site D 38/25, respectively. The remaining 47 subjects were not included in final analyses for reasons such as excessive motion during image acquisition, refusal to be scanned, claustrophobia or discomfort during MRI scanning, refusal to schedule or show up to appointments, or a determination of ineligibility based on screening exams and tests.
All subjects were between the ages of 18 and 60 and spoke English as their native language. To be included in the schizophrenia cohort, patients had to meet DSM-IV diagnostic criteria for schizophrenia, schizoaffective disorder or schizophreniform disorder. Concerted effort was made to recruit patients early in the course of their illness and especially those who were antipsychotic drug naïve.
The healthy control subjects with no current or past history of psychiatric illness including substance abuse or dependence were matched within site to the patient cohort for age, sex, and parental education (Table 2). Control subjects who had not been diagnosed with any psychiatric disorders, but had been medicated with antidepressants, anti-anxiety medication or medication for sleep disturbance were included in the study provided that the duration of their medication did not exceed 2 months of lifetime use and no medication was used within the 6 months preceding the baseline MRI scan.
Control subjects who met criteria for current or past history of substance abuse or dependence were excluded from the study. Patients, however, were not excluded from the study unless criteria were met for current (i.e., within the past month) abuse or dependence except for 6 patients who were found to meet criteria for current abuse after the study data was collected. This information is clearly marked in the shared clinical data.
Both patients and controls were excluded if they had 1) an IQ less than 70 based on a standardized IQ test, 2) history of a head injury resulting in prolonged loss of consciousness, neurosurgical procedure, neurological disease, history of skull fracture, severe or disabling medical conditions, or 3) a contraindication for MRI scanning such as pregnancy, metal in body or head including implanted pacemaker, medication pump, vagal stimulator, deep brain stimulator, implanted TENS unit, or ventriculo-peritoneal shunt.
Clinical teams at each of the sites recruited the patients. Primary treating clinicians, not necessarily involved with the study, identified potential patients who met inclusion/exclusion criteria and were competent to give informed consent. Healthy control subjects were recruited from the community at each of the sites through posters, brochures, newspapers, website advertisements, and institutional subject recruitment resources. All subjects provided informed consent to participate in the study that was approved by the human research committees at each of the sites (UNM HRRC #03-429; UMinn IRB #0404M59124; MGH IRB# 2004P001360; UIowa IRB #1998010017). In addition to the informed consent, all patients successfully completed a questionnaire verifying that they understood the study procedures.