People have been meditating/praying/whatever for thousands of years, so it is probably helping people some how.
Most of the day I working, and after that running around getting dinner, doing chores and running errands. Even if I am playing a video game I am making an effort to something. Even reading or watching a movie I am working to concentrate , watch and understand.
If I go to a quiet, comfortable place and just relax for a few minutes, my brain goes from a harried state of going from one task to another to one where it can just relax.
I suppose woo-woo can surround it. Maybe once a month I think to meditate, although in the past I have done it more.
For myself, meditating tends to relax me if I have had a harrying, stressful day. It decreases my anxiety. It has never caused an anxiety attack or the like.
If I sat down to meditate for some time, and became aware that I was very anxious, I would not think I was anxious due to meditating, as what is anxiety creating about sitting down and doing nothing (unless you have something urgent to do - then you just don't sit down and meditate)? My perception would probably be that I was already existing in a state of anxiety much of the time, and did not think about it much of the time due to the quotidian tasks that were to be performed, but now that those were not around, I could finally be made aware of the mental state I am in and do not have to push aside for something else. Perhaps a sensory deprivation tank can cause reactions in emotionally stable people, but I don't see how meditating for a few minutes/hours can. In a non meditative way I suppose logical self-reflection can be initially unpleasant for some people, meditating in a way is self-reflection on one's current natural emotional state when quotidian distractions are pushed aside, and I suppose some people who have had "bouts of mild anxiety and depression" might "meltdown" when they decide to start to come to terms with their anxiety and depression.