Recent findings indicated a polygenic risk gradient across schizophrenia and bipolar disorder, which was associated with the presence and severity of mood-incongruent psychotic symptoms.
“Mood-incongruent psychotic features are associated with poor prognosis and poor lithium response and are qualitatively similar to the prototypic symptoms of [schizophrenia], suggesting that [bipolar disorder] with psychosis and particularly mood-incongruent psychotic features may specify a subgroup or stratum with stronger etiological links to [schizophrenia],” Judith Allardyce, MRCPsych, PhD, of Cardiff University, Wales, and colleagues wrote. “Stratified linkage and candidate-gene studies of [bipolar disorder] associations with chromosomal regions and genes implicated in [schizophrenia]show stronger effects in psychosis and mood-incongruent subsamples, providing some support for this causal heterogeneity hypothesis; however, lack of consistency in earlier linkage and candidate-gene studies renders the overall support weak.”