Transdiagnostic neurocognitive deficits in patients with type 2 diabetes mellitus, major depressive disorder, bipolar disorder, and schizophrenia: A 1-year follow-up study

BackgroundImpairments in neurocognition are critical factors in patients with major depressive disorder (MDD), bipolar disorder (BD), and schizophrenia (SZ), and also in those with somatic diseases such as type 2 diabetes mellitus (T2DM). Intriguingly, these severe mental illnesses are associated with an increased co-occurrence of diabetes (direct comorbidity). This study sought to investigate the neurocognition and social functioning across T2DM, MDD, BD, and SZ using a transdiagnostic and longitudinal approach. MethodsA total of 165 subjects, including 30 with SZ, 42 with BD, 35 with MDD, 30 with T2DM, and 28 healthy controls (HC), were assessed twice at a 1-year interval using a comprehensive, integrated test battery on neuropsychological and social functioning. ResultsCommon neurocognitive impairments in somatic and psychiatric disorders were identified, including deficits in short-term memory and cognitive reserve (p < 0.01; {eta}2p = 0.08-0.31). Social functioning impairments were observed in almost all the disorders (p < 0.0001; {eta}2p = 0.29-0.49). Transdiagnostic deficits remained stable across the 1-year follow-up (p < 0.001; {eta}2p = 0.13-0.43) and could accurately differentiate individuals with somatic and psychiatric disorders ({chi}2 = 48.0, p < 0.0001). ConclusionsThis longitudinal study provides evidence of the overlap in neurocognition deficits across somatic and psychiatric diagnostic categories, such as T2DM, MDD, BD, and SZ, which have high comorbidity. This overlap may be a result of shared genetic and environmental etiological factors. The findings further lay forth promising avenues for research on transdiagnostic phenotypes of neurocognition in these disorders, in addition to their biological bases.