“It only happens to people who are mentally ill”

This one sounds progressive. It is usually deployed to argue that suicide is a health problem rather than a moral failing, which is a good argument — and the overcorrection quietly excludes a lot of people from asking for help.

What is actually the case

Mental illness raises risk substantially. Depression, bipolar disorder, psychosis, eating disorders and substance dependence all carry markedly elevated risk, and treating them is one of the most effective things available.

But a substantial minority of people who die by suicide have no diagnosed mental illness at all. Estimates vary by country and by method of study — partly because diagnoses are frequently assigned retrospectively by researchers rather than by a clinician who met the person — but no serious estimate puts it at zero, and several put it at a third or more.

What else does the work

Circumstances. Debt, unemployment, housing loss, legal trouble, shame, imminent exposure. These are not symptoms; they are events, and they can produce an acute suicidal crisis in somebody with no psychiatric history at all. Money, debt and mental health →

Loss. Bereavement, separation, the end of a career or an identity.

Isolation. Not merely being alone, but the sense of not mattering to anyone.

Pain and physical illness. Chronic pain in particular is a substantial and under-discussed factor.

Acute intoxication. Which lowers the threshold for acting on a thought that might otherwise have passed. Alcohol and low mood →

Usually several at once, arriving in a short period.

Why this matters practically

People self-exclude. Someone who is not mentally ill by their own reckoning — just ruined, or ashamed, or exhausted — reads "suicide is a mental health issue" and concludes that crisis services are not for them. They are.

It sends people to the wrong door. For a person whose crisis is a debt they cannot pay, a psychiatric referral may be less useful than a free debt adviser and a Breathing Space. Both are worth having; only one addresses the thing.

It lets institutions off. If suicide is purely a medical event, then working conditions, benefit sanctions, housing policy and how debt is collected are somebody else's department. They are not.

The version worth keeping

The useful part of the original claim is that suicide is not a character flaw, not a sin, and not a rational conclusion arrived at by clear thinking. That is right and worth defending.

The better framing is not "it is always an illness" but that it happens to people in states — sometimes illness, sometimes circumstance, usually both — which are temporary, treatable, and survivable far more often than they feel.