You are being fooled about mental illness
It's not illness
It's not dysfunction
It's not biological
It's not medical
It's not chemical
It. Is. Meaningful.
From the very inception of the medical model of mental distress, psychiatry (and I include all other mental health professions) has put itself on a path to destruction by painting itself into a corner where it must admit it is not a medical profession unto itself.
Psychiatry started out as the application of medical science to discover medical causes of and treatments for distressing experiences and behaviors. For over two centuries though, it has failed to discover any such causes. Yet, this failed campaign continues in vain. It is bad enough that this is the present state of the profession - seeking a fantasy - but there's a more damning issue that is becoming clearer and clearer. If psychiatry ever did find those elusive bits of brain or body physiology that cause human distress, it would no longer be psychiatry!
This is because all medical specialities, except psychiatry, have a bodily organ or system as its focus. Pathology within that organ or system becomes that specialty's target of assessment and care. Psychiatry has no such system or focus because all are already taken by those other specialties. If faulty brain chemistry or dysfunctional neural circuits cause mental distress, that is handled by neurology, not psychiatry. If endocrine flaws cause mental distress, that is endocrinology, not psychiatry. If nutritional deficiencies cause mental distress, that is nutritional science, not psychiatry. If genetic anomalies cause mental distress, that is handled by genetics, not psychiatry. In all those cases, the problem is not "mental" illness. It is straightforward illness.
The best (and an important) role for psychiatry to play is in helping to identify what bodily pathology is likely causing mental distress and wayward conduct, and then to hand it over to the specialty that deals with that bodily system. When no pathology can be found or reasonably theorized, it is not an illness or medical matter. Still, thousands of mental health professionals ignore this consulting role for psychiatry and march on, seeking fantastical anomalies in people and doling out even more fantastical cures.
Calling a problem "mental" illness obscures the real cause and solution.