Hi Jerald, thanks for your question.  

HBO has not been used extensively for generalized depression or anxiety as  primary diagnoses and a literature review of HBO therapy for mental illness including depression and generalized anxiety disorder yielded no clinical studies showing effectiveness of HBO for these as stand alone diagnoses, https://www.ncbi.nlm.nih.gov/books/NBK253751/ .  

When depression and anxiety are components of other diagnosis such as combat associated PTSD without TBI and treated with HBO, depression was statistically improved but not anxiety, see recent publication https://ow.ly/PHrk50U4Ny2. 

Depression and anxiety can also be components of  the Long Covid diagnosis as well, and recent studies have shown short and long term (>1 year) statistically significant improvements in depression and anxiety in the HBO treated group, https://www.nature.com/articles/s41598-024-53091-3

I hope this helps. 

Craig Lindsey, MD