No studies have examined the effects of fronto-temporal
transcranial direct current stimulation (
tDCS) on cognitive insight and neurocognitive function in
schizophrenia patients and the dynamic interplay between
tDCS-induced changes in these two outcomes. In this double-blind, randomized,
sham-controlled study, we investigated the effects of fronto-temporal
tDCS [
anode corresponding to left dorsolateral prefrontal cortex and cathode to left temporo-parietal junction; 2-mA, twice-daily sessions for 5 days] on illness severity, psychosocial functioning, cognitive insight and neurocognitive function in
schizophrenia patients (N = 60). The authors observed significant trends that
tDCS ameliorated the severity of total and general psychopathology as measured by the Positive and Negative Syndrome Scale. No significant effects were observed for other psychopathological symptoms and psychosocial functioning. Cognitive insight as measured by the Beck Cognitive Insight Scale (BCIS) was rapidly enhanced by 10-session
tDCS (F = 10.80, Cohen's d = 0.44, p = 0.002) but the beneficial effect became borderline significant 1 month after stimulation. A trend-level improvement with
tDCS of planning ability (F = 6.40, Cohen's d = 0.339, p = 0.014) as measured by the accuracy in Tower of London task was also observed. In the active
tDCS group, the change in cognitive insight from baseline to immediately after
tDCS assessment was positively correlated with that in planning ability (r = 0.46, p = 0.015), which was independent of the corresponding change in illness severity. The promising results regarding the fast-acting beneficial effects of
tDCS on cognitive insight and planning ability in
schizophrenia require confirmation in future replication studies.