Efficacy of Transcranial Direct Current Stimulation in Treatment of Cognitive Deficits in Early Stages of Psychosis

Evaluation of the Efficacy of Transcranial Direct Current Stimulation in the Treatment of Cognitive Symptomatology in the Early Stages of Psychosis: Study Protocol of a Double-blind Randomized Controlled Trial

Background: Cognitive deficits are a core symptom of schizophrenia even at the early stages of psychosis. To date, there has been reliable evidence that cognitive deficits are associated with outcomes in schizophrenia and early treatment could help to reduce the prominent disabling cognitive symptomatology which most schizophrenia patients still experience persistently. Outcomes in studies of repetitive transcranial magnetic stimulation in schizophrenia patients suggest the possibility that application of transcranial direct-current stimulation (tDCS) with inhibitory stimulation over the left temporo-parietal cortex and excitatory stimulation over the left dorsolateral prefrontal cortex could affect positive and negative symptoms, respectively. Positive effects of tDCS have also been reported on cognitive symptoms. The present study protocol hypothesis is that the development and utilization of potentially effective neuroenhancement tools such as a non-invasive brain stimulation technique like tDCS for the treatment and rehabilitation of cognitive impairment in early stages of Schizophrenia may contribute to the elucidation of the nature of the complex and dynamic processes in the brain during the early stages of the disease, and may lead to a better outcome.

Objectives: The aim of the present study protocol is to evaluate the efficacy of tDCS in the treatment of cognitive symptomatology in the early stages of psychosis.

Methods: Sixty patients in the early stages of psychosis will be randomly allocated to receive 20 minutes of active 2-mA tDCS or sham stimulation once a day on 10 consecutive weekdays. The anode will be placed over the left dorsolateral prefrontal cortex and the cathode over the left temporo-parietal cortex. Neuropsychological and psychiatric assessments will be performed at the time of consent (baseline), at 1 and 3 months following the end of the intervention (maintenance effect).

The design of the present study protocol is a double-blind placebo controlled randomised clinical trial.

After being randomly allocated, the experimental group will receive a 20 minutes of active 2-mA tDCS once a day on 10 consecutive weekdays. The control group will receive a sham stimulation (placebo), which chosen parameters consists in after 40 seconds of real stimulation (2 mA), only a small current pulse occurred every 550 msec (110 mA over 15 msec) through the remainder of the 20-minute period.

Neuropsychological and psychiatric assessments will be performed at the time of consent (baseline), and at 1 and 3 months following the end of the intervention (maintenance effect). The primary outcome will be cognitive function and the second outcomes will be the positive and negative symptoms. Outcome assessments will be performed by trial research staff. Primary and second outcomes assessors (neuropsychologists and psychiatrists) and patients will be blinded to randomized allocation after assignment to interventions.

Inclusion Criteria:

The inclusion criteria include:

1. subjects of both gender, diagnosed with schizophrenia in early stage psychosis (first five years of illness), confirmed through the Structured Interview of the American Psychiatric Association Diagnostic and Statistical Manual of Mental Disorders - 4th edition (SCID-IV);
2. aged 17-60 years;
3. minimum of 4 years of schooling;
4. Intelligent Quotient (IQ) from low average to higher scores (IQ>70);
5. and the subjects should be receiving stable doses of antipsychotics for at least four weeks (antipsychotic dose stability criterion).

Exclusion Criteria:

1. presence of a history of cranioencephalic trauma with loss of consciousness with a time greater than 5 minutes;
2. history of central nervous system diseases that affect the brain;
3. unstable clinical conditions;
4. current diagnosis of substance abuse;
5. history of substance dependence in the last 6 months, except nicotine addiction;
6. current diagnosis of another Axis I condition, confirmed through SCID-IV.