The title speaks of religion as being harmful and then the study speaks of worshipping god as being harmful or not healthy. I think both are not always inclusive or go together.
A religion, like buddhism, does not preach or worships a god, and a deist, does not belong to a religion.

Nevertheless I am of firm opposition to somebody forcing a belief on you and religious people try to do this sometimes. Yet, most of “my” heroes have been religious or believers (Ghandi, M. L. King, Tolstoy, etc.)
If a person is happy and feels his/her life to be meaningful while believing in god, as long as it is personal and not preachy (or at least accepts divergence in belief and favors discussion over blasphemy insults ), I see no problem with them.

I wrote a post on atheism, if you would like to read it, when you have time of course (you seem very busy), here the post: http://philosophicalmusingsofacybernaut.blogspot.com/2010/03/demarcations-in-atheism.html