If you are using an antidepressant, consult your physician before taking any supplement, as cases of harmful interactions between certain supplements and antidepressants have been reported (e.g., between S-Adenosyl methionine and clomipramine[1]).
With that in mind, several supplements and herbal remedies have been examined for depression including fish oil, saffron, curcumin, and zinc.
St. John's wort (Hypericum perforatum, or HP) has shown promise as an effective treatment for mild-to-moderate depression. Several studies have investigated its clinical impact by comparing the Hamilton Depression Rating Scale (HAMD) scores of people taking HP with those of people taking a placebo or traditional antidepressant medications. Some of these studies found that HP extracts have similar antidepressant properties and remission rate to serotonin reuptake inhibitors (SSRIs), with a lower rate of treatment discontinuation due to side effects.[2][3][4] When compared to tricyclic antidepressants (TCAs), HP appears to cause fewer side effects and have lower dropout rates.[4] However, it’s important to note that St. John’s Wort can adversely interact with many pharmaceuticals, including some antidepressants.[2][5][6]