Are most personality disorders really trust disorders?

Unlike other social species, we trust selectively; we choose who we cooperate with. We have exerted evolutionary pressure on each other to to judge well who is worthy of our trust, as well as evolutionary pressure to be (selectively) trustworthy. For more detail, see The biological function of love for non-kin is to gain the trust of people we cannot deceive.

This is not true for our closest primate relatives, so it is an evolutionarily recent phenomenon. We can therefore expect it is not mature and stable across the entire population. I believe this is indeed observable, and propose that most personality disorders are how we perceive people in whom this ability is malfunctioning.

Phenotype (summary)Malfunction of trust cognition
Anti-socialA long-term pattern of manipulating, exploiting, or violating the rights of othersInability or near-inability to care and therefore be trustworthy.
Avoi-dantVery shy; feels inferior a lot; usually avoids people due to fear of rejectionToo low expectation of trust from others.
Bor-der-lineLots of trouble managing emotions; impulsive; uncertain self-image; very troubled relationships.Randomness in computation of trust and trustworthiness.
De-pen-dentOver-dependence on others; may let others treat them badly out of fear of losing the relationship.Too high expectation others will care and therefore be trustworthy.
Hist-rionicDramatic, strong emotions, always wanting attention from others.Too low expectation others will care and therefore be trustworthy.
Nar-cissis-ticLacks empathy, wants to be admired by others, expects special treatment.Too high expectation of trust from others.
Para-noidExtreme fear and distrust of others.Inability or near-inability to trust.
Schiz-oidPrefers to be alone; disinterest in having relationships with others.Understanding trust is too effortful, so often not worth the trouble.

However, depressive, obsessive-compulsive and schizotypal personality disorder do not fit neatly into this frame. I propose these are different things, namely persistent forms of depression, OCD and schizophrenia respectively, that are mild enough not to have been weeded out of the gene pool despite their persistence.

So why consider this hypothesis of the pathogenesis of these disorders? Because it takes eight problems currently considered tied up with personal identy and essentially unsolvable (although talk therapy is sometimes claimed to do some good around the edges) and turns them into deficiencies in a skill that could be learnable and teachable. So this is a set of eight testable predictions. It claims that patients suffering from these eight disorders could be helped through focused training in how to handle trust correctly.

Until we know whether there is any truth to this at all, it is probably too early to know whether eight different trainings are usefully more effective than a general one, or at what age of cognitive development an intervention would be most effective.