- Introduction Preliminary data suggests that caloric vestibular nerve stimulation (CVS) single session application of cold water to the left ear induces a clinically significant, short-lived beneficial effect on specific types of illness denial (i.e., anosognosia) and delusions (i.e., somatic type). Methods We recently studied the effect of left versus right ear ice water (4°C) CVS on delusions and insight of illness in a patient with manic episode due to schizoaffective disorder. The patient was evaluated at baseline, immediately after the CVS, and then at 20 minutes, 60 minutes, and 24 hours. The method was first applied to one ear and 4 days later to the other. To assess whether the effect is specific to mania we employed the same procedure in two other patients with schizophrenia who also demonstrated delusions and impaired insight. Results All three patients showed a difference favoring left versus right ear CVS that was maintained for 20 minutes, and diminished over a 60 minute period. EEG analyses showed a numerically non-significant increase in bilateral frontal and central alpha EEG band activation (more pronounced in the right hemisphere) with left but not right ear CVS 5 minutes after the CVS, and that diminished after 20 minutes. Discussion The results suggest that left versus right CVS may have a short lived beneficial effect on manic delusions and insight of illness that seem to appear in other types of psychoses (i.e., schizophrenia). Conclusion These preliminary results suggest that single session CVS may have short lived beneficial effects in mania and perhaps in other types of psychoses. Further research is mandatory.