Effect of tDCS Timing on Safety Memory in PTSD

The primary purpose of this study is to investigate the effects of tDCS timing on safety memory in PTSD. A total of 90 participants will be randomized equally across one of three groups:

1. One group receiving active stimulation during extinction and sham during consolidation
2. One group receiving sham stimulation during extinction and active during consolidation
3. One group receiving sham stimulation both during extinction and consolidation

This study will also include an online sub-study focused on contextual processing along the PTSD spectrum. A maximum of 500 participants will be recruited using an online, panel-based platform.

This is a three-arm study composed of four to five visits over an approximate period of three weeks. Ninety participants will be exposed to a fear conditioning, extinction and recall paradigm at three separate study visits; one of these study visits will include active or sham transcranial direct current stimulation (tDCS) for a period of 15-20 minutes. Additional study procedures will include a screening period and two optional MRI scans, one done on study day 2 and one done on study day 5.

SUB-STUDY: The objective of this sub-study is to test performance differences between configural and elemental contextual processing in individuals across the PTSD spectrum using an online, panel-based platform. Following a within-subjects study design, up to 500 adult participants, 18-89 years, will be asked to complete experimental tasks that assess configural and elemental contextual learning and memory. They will also provide demographic information and complete questionnaires.

Eligibility Criteria:
Inclusion Criteria:

1. Primary diagnosis of PTSD, assessed by the Structured Clinical Interview of DSM-5 (SCID);
2. aged 18-70;
3. ability to speak, read, write, and understand English sufficiently well to complete study procedures and provide informed consent;
4. Stable psychiatric medication use or treatment for at least 6 weeks.

Exclusion Criteria:

1. Lifetime history of psychotic or bipolar disorder;
2. Current moderate or severe substance use disorder; if mild, not under the influence at time of study participation;
3. Acute suicidal or homicidal ideation as detected on screening instruments or in the investigator team's opinion, is likely to attempt suicide within 6 months;
4. current (or past) significant neurological disorder, injury, or other intracranial pathology including severe traumatic brain injury or lifetime history of a) seizure disorder b) primary or secondary CNS tumors c) stroke or d) cerebral aneurysm;
5. lifetime history of moderate or, current unstable medical conditions;
6. Any problems that would interfere with study participation, including MRI- or tDCS-related contraindications (e.g., implanted metallic devices/substances, metallic tattoos, pregnancy, claustrophobia, holes in the skull, skin abnormalities under stimulation sites), or indication of colorblindness, or presence of any other condition or circumstance that, in the opinion of the investigator team, has the potential to prevent study completion and/or inability to schedule visit days within the allotted time, and/or to have a confounding effect on outcome assessments.

SUB-STUDY Inclusion criteria: aged 18+