Diathesis

Diathesis is an underlying biological, genetic, or temperamental vulnerability that increases a person’s likelihood of developing a particular mental illness, without being a diagnosis in itself. In the stress–diathesis model, a diathesis remains latent unless activated by environmental stressors, such as trauma, sleep disruption, substance use, or major life changes. Importantly, a diathesis may never become clinically expressed. A person may carry a bipolar diathesis — sometimes called bipolar vulnerability — due to family history, circadian rhythm sensitivity, or temperament (high reward sensitivity). This vulnerability can exist for years, or a lifetime, without meeting criteria for bipolar disorder. In some individuals, stressors trigger the emergence of hypomania, mania, or major depression; in others, the vulnerability remains unexpressed. Diathesis applies broadly across other genetically influenced mental illnesses, including major depressive disorder (MDD), schizophrenia, and some anxiety disorders. Across conditions, a diathesis reflects risk without destiny: describing susceptibility, not inevitability. Also see Prodromal Traits or Phase