There’s alot of information in the northern hemisphere surrounding depression at the moment.
2 studies have shown that mild to moderate (not severe) depression is not helped by anti-depressants, specifically SSRI (eg Prozac & Zoloft) and Tricyclic drugs. Talking & placebo have the SAME benefits!
Additionally, Omega 3 (eg fish oil) & Omega 6 (eg flaxseed) deficiencies can increase emotional disorders. If cows were fed only grass, were allowed to roam free then their meat would contain more Omega 3. As it stands fish or supplements are required to get enough.
Antioxidants (colourful fruit & veg) and probiotics (eg yoghurt, green veg) can also help regulate mood.
For more information on the studies go here.