Why Won't depression go away? scientists scan brains for answers

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Key inclusion criteria for the MDD patients: * DSM-5 criteria for a Major Depressive Episode (MDE) within a MDD, confirmed through MINI diagnosis (Sheehan et al, 2015) * Age between 25 and 65 years * Hamilton Depression Rating Scale - 17 item (HRSD-17; Hamilton, 1960) \> 14 (moderate to severe symptoms) * Free of psychotropic medications (with the exception of SSRIs or SNRIs) for at least 5 half-lives before PET scanning per investigator discretion, after which an insignificant amount of drug is circulating through the body and accessing the brain. This determination will be based on self-report from the participant of when their last dose was. Use of benzodiazepines (except for diazepam) or sedative hypnotics (e.g. zopiclone) is allowable, but the last dose must be at least 72 hours prior to scanning. * Ability to undergo MRI scanning (absence of metal, pacemakers, etc.) * For non-resistant patients: Previous history of response to an antidepressant, in order to increase signal to noise between resistant and non-resistant patients Key inclusion criteria for the Healthy Controls: * Ages between 25 and 65 years * Ability to undergo MRI scanning (absence of metal, pacemakers, etc.) Exclusion Criteria: Key exclusion criteria for the MDD patients: * Pregnancy/lactation * Medical condition requiring immediate investigation or treatment * Recent (\< 6 months)/current history of drug abuse/dependence * Lifetime history of psychosis, other Axis I comorbidities are allowable * Use of any psychotropic use within 5 half-lives before the PET scanning, with the exception of SSRIs and SNRIs * For non-resistant patients: Failure of \> 2 antidepressant treatments of adequate dose and duration for current MDE. Key exclusion criteria for the Healthy Controls: * Pregnancy/lactation * Medical condition requiring immediate investigation or treatment * Lifetime history of any psychiatric disorder * Lifetime history of receiving an antidepressant