What is the strongest predictor of suicide among the following options?

The strongest predictor of suicide is a prior history of suicide attempts. Individuals who have previously attempted suicide are at a significantly elevated risk of attempting again or completing suicide in the future. This correlation exists because previous attempts often reflect underlying mental health issues, emotional distress, and the presence of risk factors that can exacerbate suicidal thoughts or behaviors. Research overwhelmingly shows that a history of attempts is one of the most reliable indicators of future risk and is central to understanding an individual's suicidal trajectory.

In contrast, while access to firearms, history of depression, and male sex are relevant factors that can contribute to suicide risk, they do not carry the same weight as a prior suicide attempt. Access to firearms may increase the lethality of attempts, but it doesn’t inherently indicate risk without other contextual factors. Similarly, a history of depression is a significant risk factor, but not everyone with depression will attempt suicide. Male sex is associated with higher completion rates of suicide, but again, it does not serve as a direct predictor in the same way that a prior attempt does. Thus, having previously attempted suicide is the most direct and reliable predictor of future suicidal behavior.