When I was interviewing people who take digital Sabbaths, one of the ways they often described themselves was as spiritual, but not particularly religious. I puzzled over this a bit, talked to a rabbi about what he thought it meant, then moved on. But (via Damon Young) I saw a piece by Mark Vernon on a new study published in the British Journal of Psychiatry that found that people who describe themselves as "'spiritual but not religious' are more likely to suffer
poor mental health:"

Michael King of University College London and his colleagues examined
7,400 interviews with folk in Britain, of whom 35% had a religious
understanding of life, 19% a spiritual one and 46% neither a religious
nor spiritual outlook. The analysis led to one clear conclusion. "People
who have a spiritual understanding of life in the absence of a
religious framework are vulnerable to mental disorder [dependence on
drugs, abnormal eating attitudes, anxiety, phobias and neuroses]." The
work supports evidence from other studies too.

Go read the whole thing. I'll just flag one more bit:

the research challenges the stance of those who are spiritual but not religious. It might be called the individualism delusion, the conviction that I can "do God" on my own. And yet, as the psychotherapist Donald Winnicott argued, human beings need to work through traditions to resource their personal creativity. Only in the lives of others can we make something rich of our own life. To be spiritual but not religious might be said to be like embarking on an extreme sport while refusing the support of safety procedures and the wisdom of experts who have made the jump before. Spirituality is like love: more risky than you can countenance when you're falling for it.

This resonates with the distinction between happy and meaningful lives that I wrote about recently.