http://www.businessinsider.com/countries-largest-antidepress...

Also, as the article states "It's difficult to say exactly what the data tell us.

Antidepressant use is not an accurate window into rates of depression. Instead, the popularity of antidepressants in a given country is the result of a complicated mix of depression rates, stigma, wealth, health coverage, and availability of treatment."

US seems to be leading the pack and from cross referencing https://en.wikipedia.org/wiki/List_of_countries_by_irreligio...

if we do bad statistics, we can conclude that since sweden has lower antidepressant use and higher secularity than US, religion actually causes psychiatric illness.

But what the data actually tells us is that it's pretty damn hard to pull any causality between secularism and antidepressant use.