If we are to believe John P. Doorley when he says that, "Spirituality is so important in mental and physical health because every human has within an innate impulse to know the Divine," then?
Regardless of whether or not we are brought up with some form of religious instruction, we are going to encounter the beliefs that underlie the world's major religions throughout the course of our lives. Those belief systems have reached into every compartment of modern life. They influence our ideas about death, sexuality, morality, self-worth and countless other things. For example, a person who has grown up outside of any formal Christian practices will most likely still be exposed to - and strongly influenced by - both motivational Christian spiritual quotes and the concept of Original Sin.
A religious upbringing can be valuable for people if it instills them with a belief in the human soul. This is something that modern science, which has stripped the definition of human nature down to the most mechanical (and accidental) elements, cannot provide. Religious doctrines have led people to the reassuring faith that their consciousness will survive physical death, that they can reunite with loved ones beyond this world, that they were put here by a loving creator, and that they have a special purpose by virtue of being one of God's creations.
Such beliefs fulfill a crucial need, and can soothe the existential unease that many people carry within themselves in the modern day. If we are to believe John P. Doorley when he says that, "Spirituality is so important in mental and physical health because every human has within an innate impulse to know the Divine," then it is safe to say that the modern world is working to stifle that impulse in many ways.
Unfortunately, such beliefs can also carry a high price. Within the context of Christianity we can believe that we are immortal, but then we must also believe that we are flawed. We cannot hope to live free from sin. We cannot hope to rid ourselves of the very concept of sin. The same religious teachings that can offer us spiritual assurance - the kind of assurance that "godless" science denies us - can also put us at odds with ourselves. They can lead us to doubt our own nature, to distrust our impulses and to feel that we are perched quite precariously in the universe.
This dichotomy has always been at the crux of faith. Christians throughout the ages have struggled to reconcile their own flawed natures with their God-given soul. The Bible recognizes this as well, which is why Jesus had to sacrifice himself for our sins so that we could be fit to enter the Kingdom of Heaven.
Again, we will encounter such ideas even if we do not receive any kind of religious upbringing. Our whole society is steeped with these sorts of notions. Some of our institutions are built upon them. In the end, the value of religious instruction depends upon the particular character and temperament of the person receiving it. Some will be able to latch upon the more life-affirming ideas while others will be more strongly drawn towards the concepts of guilt and punishment.
In order to achieve a degree of psychological wholeness, we each will inevitably have to examine and possibly discard the beliefs that were instilled in us over the course of growing up. We will have to form our own convictions about the nature of reality. We will face this task whether we grow up in a household dominated by religion, science, atheism or anything else. We are really only formed by our upbringing to the extent that we allow ourselves to be.