[There is alot of thing here --but again there is no ---yes or no answers--- because small studies --clinical they know it takes 3-6 weeks to alter moods ---some studies have been done on long tern chronic depression ppl suffering over 2 yrs . Science shows evidence that people undergo neurogenesis all there lives ---the studies have been tested on new drugs and old drugs to wide array of results. Example prozac to some depression has been a miracle drug for some -- where showed after few weeks they started to enjoys doing this again and feeling joy. why it doesnt work for everyone leads to alot more studies. Personally i think stress is a huge factor and once it reduced can have a major impact on depression and feeling better ---but there is no time line i could give you---- because its not known again due to its complex nature.