The hypothesis was that in comparison to non-remission participants, bipolar participants who achieve remission (defined as a Montgomery Asberg Depression Rating Scale (MADRS) score <12 at week 12) associated with lamotrigine monotherapy will exhibit a greater decrease in glutamate (Glu) and an increase in N-acetyl aspartate (NAA), reported as a cerebrospinal fluid (CSF)-corrected absolute concentration percent change from baseline to endpoint in anterior cingulate (AC) and dorsolateral prefrontal cortex (DLPFC).