Thanks for your comment. There are different hypotheses about what compounds in chocolate, if any, might have a significant antidepressant effect, and these hypotheses have varying degrees of (generally inconclusive) evidence to support them.

Phenylethylamine is one idea that’s been tossed out, but keep in mind that phenylethylamine tends to get metabolized before reaching the brain. It’s not even clear that the phenylethylamine in chocolate increases levels of phenethylamine in the brain. Flavanoids are another type of compound in chocolate that have gotten attention (e.g., see this review), but the idea that these give chocolate antidepressant properties is still speculative. Another hypothesis is that chocolate boosts people’s moods just because people enjoy eating it. As I mentioned in the article, scientists are still trying to figure out to what extent chocolate even causes the decrease in depression risk observed and to what extent it’s just another example of correlation-but-not-causation, which is very common in psychology/epidemiological studies.