Pranayama is typically fast breathing, and sometimes continuous in/out breathing. it's very different from the 4x4 breathing mentioned in this thread.
I am healing trauma and my experience with pranayama is that it doesn't help. Pranayama excitest he nervous system, thus causes more upset. Pranayama is something you should do when you are emotionally stable.
You can see that it excites the nervous system because you get tingly sensations coursing in your arms, or legs, or various places.
What I found from personal experience having done meditation and vipassana before, is that it isn't necessary to deliberately work with the nervous system.
If anything, I'd recommend the opposite to anybody. Try to RELAX as much as possible again and again. The extent to which you can not fully relax and sink into your sofa at the end of the day, AND forget about everything and be fully engaged in the present and what you're watching (if you're watching tv)... THAT is the extent to which there are tensions in the body that are in fact TIGHTENING and constricting the flow of energy. And by energy I mean here, science doesn't have words for that yet. Go figure, I think it's mostly blood flow but some of it can be nervous system related as well.
Put it simply: rather than excite the nervous system to supposedly make it stronger, you relax the bodily tensions so that the VITALITY that is already present and always there can move unimpeded. This is admittedly a view closer to that of bioenergetics, and I find it matches VERY closesly to my experience healing trauma.
That is why anxiety is the way it is. If it was a "charge" in the body, then you'd spend it and be done with it. And yet, it seems endless. It's seemingly endless because it's always created right there in the moment. It is the very vitality of the nervous system that is continually impeded by bodily tensions. The mind is what keeps those tensions in place.
Yoga in a sense also excites the nervous system by opening up the tensions, but it's much softer and safer than pranayama.
I know for fact that it excites the nervous system since I am healing trauma I can feel the agitation in me after each yoga class. First, it feels good but by the time I'm home 1h later... I feel agitated... I have to force myself to settle down and then relax with the tv for 30min to an hour. WHich is a very good practice. I suspect a lot of people don't realize that dimension of yoga because as soon as they're out of the class they keep getting busy. If you however try to be still after yoga, then it can be a good practice to try and relax into it.
So TLDR don't do pranayama (fast breathing) with SIGNIFICANT (ie. many years) anxiety and/or depression. While you may have a few pleasant highs, you'll end up adding more tension and cause more agitation.
My advice is to find a good yoga class, and do the slow breathing throughout the whole class. Typically breathing in and out in sync with slowly opening/closing arms/legs/whatever posture it is.
Whatever pranayama does for you, the signs of coming out of a state of vigilance in the body are:
- vision feels like it opens up, more panoramic
- colours sometimes feel more vibrant, blacks look deeper
- you notice smells you didn't notice before
- you feel areas of the body more than you used to
- hands feel very soft
- hands are warmer, more often than before, sometimes REALLY warm which is super nice then you can rest a hand on your chest or diaphragm area
- the mind calms down
- in general due to all of this you feel more "anchored" in present experience for lack of better world