Characterizing cognitive heterogeneity on the schizophrenia-bipolar disorder spectrum

Area of Science:

• Neuroscience
• Psychiatry
• Cognitive Psychology

Background:

• Group-average analyses indicate quantitative, not qualitative, cognitive differences between schizophrenia (SZ) and bipolar disorder (BD).
• Cognitive heterogeneity within SZ and BD is increasingly recognized, but its impact on between-group comparisons is unclear.
• This study investigates whether cognitive subgroups identified within each disorder uphold group-average findings.

Purpose of the Study:

• To identify cognitive subgroups within large samples of SZ and BD patients independently.
• To compare cognitive profiles across these identified subgroups.
• To explore the utility of a cross-diagnostic clustering approach for understanding cognitive heterogeneity.

Main Methods:

• Hierarchical clustering analyses were performed on cognitive data.
• The study included 1541 participants: 564 with SZ, 402 with BD, and 575 healthy controls.
• Cognitive data from participants with SZ and BD were analyzed both independently and through a cross-diagnostic approach.

Main Results:

• Three qualitatively and quantitatively similar clusters emerged within both SZ and BD groups: severely impaired, mild-moderately impaired, and relatively intact cognitive clusters.
• A cross-diagnostic clustering solution also yielded three subgroups.
• The cross-diagnostic clustering approach was more effective at reducing cognitive heterogeneity than independent disorder clustering.

Conclusions:

• Commonly observed quantitative cognitive differences between SZ and BD diminish when cognitive heterogeneity is considered.
• Corresponding cognitive subgroups across diagnoses share similar profiles, irrespective of their specific disorder.
• These findings suggest that shared cognitive risk factors may underlie cognitive impairments observed in individuals with SZ and BD.