Inclusion Criteria:

1. age between 18-35 years;
2. current DSM-IV diagnosis of schizophrenia confirmed by the Structured Clinical Interview for DSM-IV (SCID) conducted by a trained psychiatrist.
3. being at an early phase of the disorder (i.e., within five years of their first exposure to neuroleptic treatment;18)
4. did not receive antipsychotic treatment for six months preceding current symptom exacerbation;
5. baseline total score of more than 60 on the Positive and Negative Syndrome Scale (PANSS).
6. Initiation of treatment with atypical antipsychotic medication equal or less than 14 days prior to study entry (risperidone, olanzapine, quetiapine, or clozapine; 200-600 mg/day chlorpromazine equivalent doses);
7. able to comprehend the procedure and aims of the study.

Exclusion Criteria:

1. acute, unstable, significant or untreated medical illness beside schizophrenia;
2. pregnant or breast-feeding females;
3. A DSM-IV diagnosis of substance abuse or dependency;
4. Known contraindication to minocycline treatment.
5. Treatment with minocycline or Beta-lactam antibiotics in the preceding half year before study entry.
6. Under compulsory hospitalization.