The authors present the main studies & conclusions of a larger systematic review of 850 studies published in the twentieth century on the relationship between religion & mental health. This paper also includes an update on research published since 2000. The majority of studies found that higher levels of religious involvement are positively associated with indicators of well-being & with less depression, suicide ideation & behaviours, & drug/alcohol abuse. Theoretical pathways of the religiousness-mental health connection & clinical implications of these findings are also discussed. (100 refs.)