It should be common knowledge by now, as the problem has been documented for decades and discussed here many times.[1][2][3][4]
As far as an actual citation: "Studies from Kjølseth et al. (2009), and our own findings (Szücs et al., 2020), suggest that older adults who die by suicide or have late-onset (mostly high-medical lethality) suicide attempts are often high-functioning throughout most of their life, and characterized as controlling, rigid, high-achievers, also high on orderliness (a conscientiousness subcomponent)."[5]