For a lot of people, especially in poorer regions, LLMs are a mental health lifeline. When someone is severely depressed they can lay in bed the whole day without doing anything. There is no impulse, as if you tried starting a car and nothing happens at all, so you can forget about taking it to the mechanic in the first place by yourself. Even in developed countries you can wait for a therapist appointment for months, and that assumes you navigated a dozen therapists that are often not organized in a centralized manner. You will get people killed like this, undoubtedly.
LLMs are far beyond the point of leading people into suicidal actions, on the other hand. At the very least they are useful to bridge the gap between suicidal thoughts appearing and actually getting to see a therapist