I've known plenty of professing Christians who definitely struggle with depression- yet what gets them through that depression is often their faith. Their depression or malaise is no different than the unbeliever excepting their faith which gives them comfort and strength
You're right, clevergirl, but we're not talking about the average religious joe struggling with a bout of depression but about religious extremism.
There may be a few general characteristics of people who turn into extremists:
1. They have a sense of absolutism: They have a distorted, nonconstructive and irrational thought that the truth, moral or aesthetic values are absolute, universal, set and unchangeable. They do not believe in change and diversity and are usually very low in their tolerance level.
2. They have a sense of righteousness: They usually think that they know the truth and no one else does. Their truth is very limited and based on outdated, contaminated and one-sided information. They usually don't even have enough knowledge about their own religion and only know the surface part.
3. They do confirmation bias: This is where one only brings in information that fits his thought process and dismisses anything else. Any other information, no matter how historically, scientifically and logically valid, will be disregarded.
4. They have a sense of knowing an ultimate meaning: They have a sense of a black and white thinking where the white is a limited definition of how life "should" be for all of us. There is no flexibility, no adaptability and no objectivity. You are either into this small and specific white zone or you are "the other."
5. They dehumanize whoever does not fit their view: They put other people's views inferior to theirs and dehumanize people whose views do not fit theirs. This gives them a sense that they have the right to kill, harm and destroy others. They also do the same to out-groups.
6. They idealize historic figures or stories: Such people usually idealize some figures in their belief system and stories attached to the past and want to fit the present and the future into that idealization.
7. They have an utter certainty that they are right: The objective mind of a rational person knows that at any time, there are so many things he does not know. But an extremist does not have such view and holds a distorted thought that he knows all the answers and has found the "truth" which is the only truth.
8. They have a sense of unwillingness to compromise: For such individuals, there is only one way and that is what matches their definition of truth. They are not willing to find common grounds with other people and cannot find win-win positions.
9. They have too much focus on the life after death: A religious extremist has too little focus on the importance of this life and what makes him feel fulfilled in it and is too attached to the concept of a "great" afterlife.
10. They have many psychological defenses: Such individuals have formed a number of psychological defenses so none of their internal feelings would be challenged.
Roya R. Rad, MA, PsyD: What Turns Ordinary People Into Religious Extremists?