[maus42]

On the contrary, the culture and the society very much influences how various mental issues develop and manifest and how they are interpreted.

You can't explain writing emails impersonating someone simply as result of "chemical imbalances in the brain" (except if you reduce every kind of human behavior to that, but then the phrase "chemical imbalance" does not explain anything). Brains and their chemical imbalances are much older than the technology of emails, or even writing.

[openasocket]

I agree that culture can very much influence the presentation of mental illness. But the ability for a culture or society to cause a mental illness in the first place is much more limited. Mental illness can be caused or exacerbated by a high stress environment or trauma, but not much else.