Depression and other ailments have been treated by artificially raising serotonin in the brain ie by using drugs. However, latest research shows that there are a number of alternate methods for doing the same thing.
The first way is commonly used for SAD (seasonal depression) but is now being used for other forms of depression as well. Bright light, raises the serotonin in the brain and the sun is the best source of bright light. Until recent times we humans were outside, hunting or farming for a great deal of the time and this is thought to have contributed to the lower rates of depression in these times.
Another natural agent which raises serotonin has been found to be exercise. This is especially so when you exercise to the stage of fatigue. So I am guessing a good brisk walk on a hilly path would be better than a light stroll around the shops.
Tryptophan also seems to increase the brains level of serotonin. Tryptophan is an amino acid and is found naturally in a number of protein foods. Not all foods provide tryptophan that makes it to the brain however and there is thought that certain foods should be bred to provide more. In other words we should not so much think of making lots of food but growing healthier food.
The research even suggests that we have inately choosen varieties of food or cooking methods in the past that increase the available tryptophan. For example wild chick peas have less available tryptophan than cultivated varieties. Corn in South america was cooked wth an alkalai which enable more tryptophan to be absorbed by the brain, but this practice did not follow corn as it moved out of south america.
The research suggests that we should spend more time looking at natural solutions rather than pharmacueical solutions and we could have a happier healthier population.