The study will consist of four phases: screening, open-label, double-blind and discontinuation phases. After screening to ensure that subjects meet the study criteria, individuals will enter an open-label (flexible-dose) trial of paroxetine-CR given in dosages up to 62.5 mg for a period of eight weeks. Paroxetine may be substituted for paroxetine-CR in dosages up to 50 mg. Subjects may be switched from paroxetine-CR to the bioequivalent dose of paroxetine due to drug supply disruption but should not be switched back to paroxetine-CR. Subjects are not allowed to switch from paroxetine to paroxetine-CR. Subjects who start on paroxetine at the first visit must remain on paroxetine for the duration of the study. At the discretion of the investigator, additional monitoring or interim visits may be needed for subjects who require a switch from paroxetine-CR to paroxetine. Those individuals who fail to respond adequately will then continue into the second phase (double-blind portion) of the study, in which participants will continue on either paroxetine-CR or paroxetine, and will be randomized to either placebo or lamotrigine in a flexible-dose design up to 400mg for a 10-week period. Subjects will remain on the same dose of paroxetine-CR or paroxetine that they were taking at the final visit in the first phase of the study (Visit 5/Week 8). The study medications will be discontinued following the final study visit (Visit 11/Week 18 or the early termination visit). Paroxetine-CR or paroxetine may be continued in the dosages used during the study after completion of the protocol if, in the judgment of the investigator, the subject has shown a partial response to treatment with the drug. The lamotrigine (or placebo) dose will be decreased by half for one week and then discontinued. Subjects will return two weeks post-study and four weeks post study for follow up visits consisting of safety evaluations. In addition, a MADRS and CGI should be performed at the two-week post study follow up visit. The visit at four weeks post study may be omitted if the 3rd and 4th week of taper are not needed. The decision to restart lamotrigine at that time would also be up to the investigator, but the dosage of lamotrigine would have to be titrated in the first month per the manufacturer's clinical trial program. This is necessary since all subjects will be discontinuing from the drug following Visit 11/Week 18 or the early termination visit in order to maintain the blind at the conclusion of each subject's participation in the study. Subjects who are discontinued from paroxetine-CR at dosages of 25 mg/day or higher should undergo a gradual dose reduction of 12.5 mg per week rather than abrupt cessation. Subjects who are discontinued from paroxetine at dosages of 20 mg/day or higher should undergo a gradual dose reduction of 10 mg per week rather than abrupt cessation.