Inclusion Criteria:

1. At least 18 years of age.
2. Veteran status
3. Clinically diagnosed with a mTBI, PCS, PTSD, Anxiety, or Depression disorder.
4. Successfully completed the parent Hyperbaric Oxygen Therapy (HBOT) intervention, consisting of the full study treatment protocol (40 HBOT sessions).
5. Willing and able to read, understand, and provide written informed consent for participation in the 12-week follow-up study. Additionally, the Participant has clear consciousness and the ability to express self-feelings independently.
6. Completed cognitive and psychological measurements.
7. Clinical diagnoses cause significant impairment in social or occupational functioning or some other functional capacity.
8. Stability on any current psychoactive medications (antidepressants, anti-anxiety medications, antipsychotics, stimulants, and mood stabilizers).

Exclusion Criteria:

1. Acute medical illness or infection
2. Severe or unstable physical disorders or major cognitive deficits
3. Current manic, psychotic episodes, or serious suicidal ideations
4. Non-English speakers
5. Inability to attend scheduled follow-up visits
6. Significant life events, new neurological injury, or new psychiatric diagnosis or hospitalization occurring after completion of the HBOT intervention that, in the opinion of the investigator, could confound cognitive, psychological, or quality-of-life outcomes.
7. Participation in another interventional clinical study or receipt of a therapeutic intervention following completion of HBOT that could influence cognitive, psychological, or quality-of-life outcomes.