Veracity full stop; I was trying to simply emphasise putting the issue of 'veracity' aside and concentrating instead on the possible effects of belief on one's mental well-being. So I was not asking about myself or anyone else believing in anything, simply wondering about the relationship between good mental health and belief. Sorry if I misled.
OK, no worries. Assuming you are talking about religious beliefs, In my experience, the biggest bennie in a strong religious belief system is something to hold onto when times get tough. There are also peripheral benefits such as being a part of a religious community (who embrace your shared beliefs) that improve mental health.
For example, I know a 30-something mom in a small community nearby that has cancer. She is part of a large Catholic church, and at a recent dinner & fundraiser for her medical expenses, 800 people turned out. That's 10% of the entire community! That had to be a huge uplift in an otherwise tough situation.
Example #2, my old Southern Baptist church used to have a "prayer circle," where when someone was sick or otherwise in need, people would start praying for them. You would receive a phone call descibing the situation and asking you to pray, and then you would have to call 2 more people that were next on the prayer circle list. While this admitedly seems a little corny if you're not a bible-thumper, it was a huge mental boost for whomever "needed" the prayers. Somehow just knowing a couple hundred people are praying for you, thinking of you, and wishing you the best brightens your day. It employs the "power of positive thinking," somewhat like a placebo effect.
Those of us that choose not to follow a particular dogma have to figure a lot out for ourselves throughout life, which can be mentally exhausting and stressful during life's tough times. And we have to work harder to be a part of a community since we don't have an "instant" church family.
We have all read studies suggesting a correlation between religious beliefs and happiness. I have also seen studies suggesting a correlation between non-theism and depression. There are many variables at play and I don't know if there is causation there or not, but it's interesting to ponder. For this reason I would never want to "take away" someone's religious faith by proselitizing my agnosticism unless they were questioning their own beliefs... (vs. the atheists that many of us have known that will try to convince any religious "believer" that they are "wrong")
Personally, since I don't have the religion advantage for mental health, I focus on maximizing the other variables that bring me happiness and mental well-being: daily exercise, time alone in nature, family, friends, meaningful/fulfilling career, volunteerism/community involvement, intellectual stimulation, art/creativity, and healthy eating. For me, religious belief is but a small part of my overall mental health. My Christian sister would argue that it is the core of her existence.
What type of beliefs did you witness at the funeral that provided food for thought?