Deficits in social cognition (SC) are significantly related to community functioning in schizophrenia (SZ). Few studies investigated longitudinal changes in SC and its impact on recovery. In the present study, we aimed: (a) to estimate the magnitude and clinical significance of SC change in outpatients with stable SZ who were assessed at baseline and after 4 years, (b) to identify predictors of reliable and clinically significant change (RCSC), and (c) to determine whether changes in SC over 4 years predicted patient recovery at follow-up.

The reliable change index was used to estimate the proportion of true change in SC, not attributable to measurement error. Stepwise multiple logistic regression models were used to identify the predictors of RCSC in a SC domain (The Awareness of Social Inference Test [TASIT]) and the effect of change in TASIT on recovery at follow-up.

In 548 participants, statistically significant improvements were found for the simple and paradoxical sarcasm of TASIT scale, and for the total score of section 2. The reliable change index was 9.8. A cut-off of 45 identified patients showing clinically significant change. Reliable change was achieved by 12.6% and RCSC by 8% of participants. Lower baseline TASIT sect. 2 score predicted reliable improvement on TASIT sect. 2. Improvement in TASIT sect. 2 scores predicted functional recovery, with a 10-point change predicting 40% increase in the probability of recovery.

The RCSC index provides a conservative way to assess the improvement in the ability to grasp sarcasm in SZ, and is associated with recovery.

Few studies have investigated alterations of olfactory neuroepithelium (ONE) as a biomarker of schizophrenia, and none its association with cognitive functioning.

Fresh ONE cells from twelve patients with schizophrenia and thirteen healthy controls were collected by nasal brushing, cultured in proper media and passed twelve times. Markers of cell proliferation (BrdU incorporation, Cyclin-D1 and p21 protein level) were quantified.Cognitive function was measured using Brief Neuropsychological Examination-2. Primary outcome: proliferation of ONE cells from schizophrenic patients at passage 3. Secondary outcome: association between alteration of cell proliferation and cognitive function.

Fresh ONE cells from patients showed a faster cell proliferation than those from healthy controls at passage 3. An opposite trend was observed at passage 9, ONE cells of patients with schizophrenia showing slower cell proliferation as compared to healthy controls. In schizophrenia, overall cognitive function (Spearman’s rho -0.657, p < 0.01), verbal memory – immediate recall, with interference at 10 s and 30 s (Spearman’s rho from -0.676 to 0.697, all p < 0.01) were inversely associated with cell proliferation at passage 3.

Fresh ONE cells collected by nasal brushing might eventually represent a tool for diagnosing schizophrenia based upon markers of cell proliferation, which can be easily implemented as single-layer culture. Cell proliferation at passage 3 can be regarded as a promising proxy of cognitive functioning in schizophrenia. Future studies should replicate these findings, and may assess whether ONE alterations are there before onset of psychosis, serving as an early sign in patients with at risk mental state.