There seems to be some confusion here. I checked my copy of DSM IV and nowhere does it use the term “mental illness.” The term was dropped years ago because it’s very imprecise and misleading, and very stigmatizing on top of it.
DSM talks about “disorders.” Mood disorder with depressed affect, or attention deficit disorder with hyperactivity. Causes aren’t given – just lists of symptoms that can point to a useful therapy.
Why? Because we really haven’t the foggiest about how to even classify these kinds of problems, let alone understand what causes them. Some are related to biochemical imbalances, some to parenting, some to a combination. We really don’t know for sure.
The best thing to do is go to a good therapist – clinical social worker or psychologist, preferably frum, and get advice and treatment. Unfortunately, we’re still so hung up over the “stigma” that people are afraid to go.
Don’t think of “illness” – think of problems in living. Who doesn’t have problems? And like most problems, there are at least partial solutions. Don’t feel badly about it and put yourself down – just get help.