Depression, feelings of hopelessness and stress do have physical affects. Many studies support that view.
There are also numerous studies, which I have read over the years which support the belief that prayer, belief in God, religious rituals and belonging to a faith community gives people hope, it takes away hopelessness, alienation and apathy. That's why people who refuse to believe or take advantage of the many benefits of belief and prayer cause me confusion. Christians as well as believers of other faiths have hope in a God who loves us and cares for us. Our God is a God of hope, a God who can bring good out of bad and bring hope and healing to the most difficult situations. Sometimes we have to be patient, for God's ways and actions cannot be comprehended, at times we can get a glimpse of God working in our world.
In these uncertain times we're living through, I don't think there are more important attitudes to have than hope, optimism and trust in God. I'm not sure how people can live without them. They are obviously good for your physical health, good for your soul and good for your relationship with God and others.
Many people are filled with anxieties and fears, there is a lot to worry about, especially if you have a tendency to worry. But with God all things are possible, with God and through prayer and perseverance, "All will be well," in the words of Julian of Norwich. I believe that, I've seen it work over and over again. God is a God of hope, not despair and anyone who distances themselves from God's love or hope is foolish, in my opinion.