Well I have not been recommended marijuana by a doctor, nor do I have that MMJ card....but I have certainly smoked marijuana to alleviate PTSD symptoms and as far as I can tell it does help. It calms the anxiety, reduces racing thoughts/being stuck in thoughts of past and generally helps with relaxation. The effects are temporary though so yeah it will wear off.

There are other ways to ingest it besides smoking, and there are strains that don't get you as high....like strains with much more CBD than THC, not sure about strains that don't get you high at all though, I personally don't really mind that effect...but to each their own.