That, alone, could point to two very obvious but very different conclusions.
One is that people in those societies need medications more.
Alternatively, people in these societies get needed medications more.
I suspect the average American gets more therapy than the average Afghan, but I suspect the Afghans would still benefit from it.
Privileged societies are more medicated because the most pressing issues to them are (somewhat) soluble using medication. Because they are not imminently worried about housing and sustenance or violence.
Would be odd to consider medicating for fibromyalgia or depression when you're starving and/or being bombed / shot at.
Generally, humans are better suited to stable and safe environments. But it would be irresponsible of genes not to include, occasionally, humans who did better in chaos because chaos frequently happens.
And yet science says the opposite. The prevailing evidence suggests that humans are generally better suited to stable and safe environments, with danger and chaos typically leading to detrimental effects on mental health.