There’s an interesting article in the most recent Amatuer Photographer magazine on photography and mental health (‘Photography saved my life‘ Saturday 24th Feb 2018). It discusses the benefits of photography for those with anxiety and depression.
It has certainly been my experience that photography often helps to create calm and peace when anxious thoughts are spiralling. As the article mentions, there are also opportunities for photographers to put too much pressure on themselves and I have occasionally found this with unfruitful attempts at street photography.
But normally, time spent walking and observing; looking for interesting shots, people or places, is therapeutic. The requisite focus, singlemindedness and awareness of your surroundings, can be a great remedy to anxiety or excessive introspection.