Published in May, 2020 by Michael Marshall in Nature is a readable, easy to understand essay about recent advances in understanding the biology of mental disorders.
Most gratifying for me is that, once again, it bears out the nonsense of traditional psychiatric diagnosis of putting human suffering in supposedly discrete boxes. The huge number of studies of various kinds Marshall reviews (I was tempted to say, 'marshalls') shows that it simply ain't so.
People at risk of one 'mental disorder' are at risk of a surprising variety of others, and many people display symptoms from a smorgasbord of 'disorders.' There is talk of dimensions instead of categories.
Rather than a few genes being responsible for any of the conditions, there are probably hundreds of genes involved, and in no clear pattern.
I can help to clear up the confusion. Um... how about what happens to people?
Oodles of research could have been included in the analysis on the effects of modelling: we react to stressful situations by copying the important figures of our infancy and childhood.
There is ample evidence that traumatic events, as perceived by a child (often, but not necessarily also considered traumatic by society) shape inner beliefs and ways of reacting.
I have set out some of the evidence in From Depression to Contentment: A self-therapy guide.