Who is more prone to depression at higher latitudes? Islanders or mainlanders?

Abstract Across 195 countries, rates of depressive disorders in women and men are higher among islanders (relative to mainlanders) at more northern locations in the Northern Hemisphere and at more southern locations in the Southern Hemisphere. Our explanatory analyses show that the three-way interaction of greater daylength variability, being more of an islander, and adopting a more individualistic culture accounts for higher rates of depression in both genders. Differences in longitude, photoperiod, phase shift, disaster risk, economic poverty, income inequality, and urbanization level do not appear to account for the oppositely sloping north-south gradients of depression above and below the equator.