From the Guardian UK

A Harvard psychologist named Gordon Allport did some key research in the 1950s on various kinds of human prejudice and came up with a definition of religiosity that is still in use today. He suggested that there were two types of religious commitment – extrinsic and intrinsic. Extrinsic religiosity he defined as religious self-centredness. Such a person goes to church or synagogue as a means to an end – for what they can get out of it. They might go to church to be seen, because it is the social norm in their society, conferring respectability or social advancement. Going to church (or synagogue) becomes a social convention.

Allport thought that intrinsic religiosity was different. He identified a group of people who were intrinsically religious, seeing their religion as an end in itself. They tended to be more deeply committed; religion became the organising principle of their lives, a central and personal experience. In support of his research, Allport found that prejudice was more common in those individuals who scored highly for extrinsic religion.

The evidence generally is that intrinsic religiosity seems to be associated with lower levels of anxiety and stress, freedom from guilt, better adjustment in society and less depression. On the other hand, extrinsic religious feelings – where religion is used as a way to belong to and prosper within a group – seem to be associated with increased tendencies to guilt, worry and anxiety.