My brother was a music student, outdoor leader, and president of his school's student union. Creative and ambitious, he dreamed of continuing our father's legacy by becoming a professional musician. Now he lives in a homeless shelter, and struggles to separate what's real from what isn't.

My girlfriend was a psychology student, varsity cyclist, and member of the poetry club. Her innocence and enthusiasm for life were irresistible; you could not be near her without feeling happier, more spontaneous and free. Now she is delusional, addicted, suicidal.

My friend's brother was another aspiring musician. He came from a healthy, loving family like mine. In university, he started having manic episodes, but refused treatment. He fled the country and moved to Ukraine, where he died last month, leaving behind a wife and unborn child.

I could go on.

Mental illness is the new cancer. It is the cancer of Generation Y, a cancer that affects more young people than any other major illness. It takes the people you love and care about, at the peak of their lives, and reduces them to ghosts. Or worse.

Illnesses like schizophrenia, bipolar disorder, and major depression often begin invisibly and fester undetected for months or years. By the time you realize there's a problem it's often too late to do anything about it. You try anyway, then discover that mental illness can be treated (if the person is willing, if the medication is right, if they heed their wellness plans) but rarely "cured."

Since I began writing about my brother, and talking to experts, I've come to realize that cancer is not a better understood disease than schizophrenia. The actual phenomenon of cancer--the random, uncontrolled division of abnormal cells--remains largely mysterious, so why does it get more attention than most, if not all, other diseases?

The answer is complicated. Physical illnesses are easier to identify, and receive more sympathy and resources. This needs to change. The same way that we recognize toxic physical environments--cities closed to radiation, houses filled with carcinogenic smoke--as causing cancer, we need to recognize toxic internal environments as having a similar effect on the mind.

Of course there are other factors: Genetics. Childhood abuse. The effect of THC on a sensitive mind. But less known factors are still important. Before he started showing psychotic symptoms, my brother was anxious, depressed, and uncertain about his future. Before my friend's brother became delusional, he was devastated by the death of his grandfather.

It's not on the list of conventionally believed causes, but unresolved emotional conflict, years from now, may well be seen as a leading cause of mental illness--the way cigarette smoke was finally linked to lung cancer. Until then we must continue to educate people about problems of the mind--and ultimately of consciousness--including the malignant forces that lead to brain disorders.