So to the question - the relationship between 'spirituality' and good mental health. The question I set out to answer long ago with Sans God and subsequently failed to answer in any meaningful way.
I guess the problem, as ever, is in the question. You see, if 'spirituality' is a duff term, then by using the same logic 'mental health' is equally flaccid.
Blood pressure we can measure, liver function can be quantised in the same way an an x-ray can tell you if your arm is broken. But mental health? Is it happiness, conforming to societal norms or a grasp on reality? And what in buggeration is that?
Yet as experts in humanity, we all have an opinion on sanity. Fair play to us too, because psychiatry hasn't cracked it either. So I shall give you my opinion, based upon nothing more than my opinionated opinion. And what better medium to spout unsubstantiated, reductive, self-centered arguments than on a blog?
So let's focus on the melancholics, worriers and scaredypants amongst us and not on those who may lay true claim to the moniker of 'madness' - the messiahs and 'psychotics'. They deserve our admiration and are beyond the scope of my thinking right now.
Feeling depressed and anxious is something common to us all. It's even been argued that they're adaptive traits. Everything in moderation however, for these states can easily get the better of us.
When they do, we can become self-destructive. Regardless of the outward circumstances of our predicament, depression or anxiety is fundamentally about the 'self' and how we see ourselves - "I'm depressed", "I'm inadequate", "Life has got the better of me".
Now, this secular definition of 'spirituality' that we've been exploring (Interconnectivity / Love / Meaning / Beauty), seems to me to be outward, rather than inward looking. The very antithesis of self-consuming neuroses, you could say.
Whilst 'spirituality' is a deeply personal phenomenon, I propose that it helps us mediate our connection with the outside world. As such, it helps us to be less absorbed with ourselves and become more immersed the world about us.
Which is a good thing, and probably better for our mental health than what's inside our heads alone.