Which of the drugs (if either) was more successful in preventing the recurrence of depression relative to the placebo?

The results clearly reveal that Imipramine is by far more effective than Lithium in preventing the recurrence of depression. 62.16% of the patients taking Lithium had a recurrence of depression which is more than twice that of patients who took Imipramine (28.95%). 

The results also question the effectiveness of Lithium in general since the percentage of patients who had a recurrence of depression in the Placebo group (67.65%) is only slightly higher than that of the Lithium group (62.16%).

Crossing over creates new combinations of genes in the gametes that are not found in either parent contributing to genetic diversity