Personality disorders and mood disorders: phenomenological resemblances vs. pathogenetic pathways.

Diagnosis in psychiatry is currently based on phenomenology, because etiology and pathogenesis are largely unknown, and because biological markers for disease have not been identified. The unitary model of depression and the model of a bipolar spectrum are based on resemblances in phenomenology between symptoms whose pathogenetic pathways are likely to differ. Both models have sometimes considered the diagnosis of personality disorder as an affective variant, even when patients present with qualitatively distinct mood features. Biological reductionism lies behind a concept of mood as the primary driver of psychopathology, a view that may be detrimental to treatment.