Palmier-Claus et al ^{Reference Palmier-Claus, Berry, Bucci, Mansell and Varese1} appear to conclude from their meta-analysis that childhood adversity is clearly, and independently, linked to developing bipolar disorder as an adult.

Surely, however, adults with bipolar disorder are hugely more likely than healthy population controls to have had parents (and other relatives) who themselves suffered from affective disorders, given the genetic heritability of these illnesses. It is surely accepted that affective disorders in parents have a negative effect on the well-being of children, and the adversity experienced by children may (at least in part) be mediated by affective disorders in their parents.

To ignore the possible effect of experiencing adverse events in childhood precisely because there was a greater likelihood of affective disorder among these children's parents seems to me to be a glaring omission in this paper.