Psychosis is an extension of mood swings from the perspective of neuronal plasticity impairments.

We previously hypothesized that depressive and manic states may be consecutive presentations of the same underlying neuronal plasticity, and that moderate impairments in neuronal plasticity cause depressive states while further impairment to neuronal plasticity causes manic states. Psychopathological or biological relationships between bipolar disorder and schizophrenia have also been revealed. Therefore, in addition to depressive and manic states, psychosis may also be considered a manifestation resulting from additional impairments to neuronal plasticity. In the present manuscript, we hypothesize that moderate and more severe impairments to neuronal plasticity cause depressive and manic states, respectively, and that more serious impairments to neuronal plasticity cause psychosis. Many studies have suggested that impairments in neuronal plasticity contribute to schizophrenia and other mental disorders with psychotic features, and that the impairment of neuronal plasticity in schizophrenia is more severe than that in bipolar disorder. Therefore, we hypothesize more specifically that impairments in neuronal plasticity may be more severe in the order of the cases featuring psychosis, mania, and depression. This progression notably overlaps with the arrangement of schizophrenia, bipolar disorder, and depressive disorder in the DSM-5. Psychotic symptoms are thought to appear further towards the base of the psychopathological hierarchy than are manic or depressive symptoms. If impairments to neuronal plasticity contribute to this psychopathological hierarchy, as we contest that they do, our hypothesis may serve as a bridge between clinical psychopathology, diagnosis, and biological psychiatry.