One surprise in these numbers is that Africa seems to be doing better than Latin America when I would have expected them to be close to each other given the economic difficulties, violence and lack of perspective for large swaths of the population.
Often times what is understood by first-worlders as "depression" is a cluster of problems that uniquely affect decently well-off people who have been spiritually and physically subjugated by an spiritually blank industrial bureaucracy. If you measure stress, hunger, sorrow, fear, scarcity, etc. you'll find higher levels among the global poor, but if you measure "malaise, sadness, lack of purpose, emptiness, yearning…
But i can see how a simpler and poorer life will remove the worries of emptiness/lack of purpose when all you can focus on is making ends meet and have enough to eat at the next meal.