Neurological soft signs and cognitive functions: Amongst euthymic bipolar I disorder cases, non-affected first degree relatives and healthy controls

• BPI participants had more NSS than unaffected first degree relatives and controls.
• No significant difference between relatives of BPI and healthy controls on NSS.
• There are significant differences between BPI patients and controls on cognition.
• There are associations between some cognitive functions and NSS in BPI patients.

Both neurological soft signs (NSS) and cognitive deficits are present among euthymic bipolar patients. NSS could be related to neurocognitive performance, but this is not explored thoroughly. Healthy relatives of patients may also suffer from similar deficits.This study compared NSS and cognitive functions in euthymic Bipolar I Disorder (BPI) cases to their non-affected first degree relatives and healthy controls. We also investigated the association between NSS and cognitive functions in these three groups. NSS were assessed in three groups using Neurological Evaluation Scale-revised (NES-r). Eight cognitive domains were assessed in 31 euthymic BPI cases, their 30 non-affected first degree relatives and 30 healthy controls using Computerized Neurocognitive Battery (CNB). Euthymic BPI patients had significantly more NSS than non-affected first degree relatives on 5/7 tests (p-value ranges from 0.042 to p = 0.0001) and healthy controls on all tests (p-value from 0.042 to <0.0001). Non-affected first degree relatives and controls did not have any significant difference. BPI participants performed worse than their non-affected first degree relatives on one neurocognitive domain of CNB (spatial memory accuracy, p = 0.03) and healthy controls on four domains (spatial memory accuracy (p = 0.04), abstraction and mental flexibility efficiency (p = 0.04), spatial memory efficiency (p = 0.04), and emotion efficiency (p = 0.04). Non-affected relatives and healthy controls were similar on neurocognitive domains. Accuracy and efficiency indices of some specific cognitive domains were negatively associated with AV rating and tap copying NSS ratings.