Natural selection is a process that affects the gene pool over generations. It favors traits that improve survival and reproduction. Suicide is an individual action, often caused by environmental, psychological, or social factors rather than purely genetic ones. Even if there were a genetic predisposition, it would not be the sole factor behind suicide.
While there may be some genetic influences on mental health conditions linked to suicide (e.g., depression, bipolar disorder), suicide itself is not a strictly heritable trait. Many people with no family history of suicide still experience suicidal thoughts due to life circumstances, trauma, or neurological imbalances. Likewise, many with a family history of suicide never experience it themselves.
Natural selection doesn't aim for happiness or well-being—it simply favors traits that lead to survival and reproduction. Plenty of people with severe mental illnesses reproduce, and many who die by suicide could have had children beforehand. Viewing suicide as "natural selection" misinterprets how evolution actually works.
Suicide is not "just natural selection" because it is not purely genetic, it is heavily influenced by external factors, and it doesn't follow the principles of evolutionary fitness. It is a complex, human issue deeply tied to mental health and societal conditions rather than an evolutionary process.