Final answer:
SSRIs are preferred over TCAs for treating depression due to a safer side effect profile and efficacy in treating both depression and anxiety. They work by increasing serotonin levels in the CNS which can improve mood.
Step-by-step explanation:
SSRIs, or Selective Serotonin Reuptake Inhibitors, are used more frequently than TCAs, or Tricyclic Antidepressants, for the treatment of depression primarily because SSRIs generally have a safer side effect profile, particularly in overdose situations. SSRIs like Prozac, Paxil, and Zoloft are known to increase the levels of serotonin in the central nervous system by blocking its reuptake, which can effectively elevate mood and also be useful in treating anxiety disorders. In addition, while some TCAs may have a modest increase in efficacy, SSRIs are generally preferred due to their fewer anticholinergic side effects and lower risk associated with overdose. It should be noted, however, that neither SSRIs nor TCAs have a significant difference in the risk of conversion to mania in patients with bipolar disorder.