Mistaken about what? What did I miss?
I read the article, and I'm obviously paraphrasing here, but I stated that whenever I either cry, or, poop, it feels as if I've ingested a low dose of a weak µ-opioid agonist such as Codeine. And although I wasn't more specific, I've suspected that it's actually due to my body's natural painkillers (or endorphins) binding themselves to µ-opioid receptors.
Enter Leucine-enkephalin:
Leu-enkephalin is an endogenous opioid peptide neurotransmitter with the amino acid sequence Tyr-Gly-Gly-Phe-Leu that is found naturally in the brains of many animals, including humans. It is one of the two forms of enkephalin; the other is met-enkephalin. The tyrosine residue at position 1 is thought to be analogous to the 3-hydroxyl group on morphine. Leu-enkephalin has agonistic actions at both the µ- and d-opioid receptors, with significantly greater preference for the latter. It has little to no effect on the kappa-opioid receptor.
So it may be possible that the aforementioned 'natural painkiller' may be binding to µ-opioid receptors whenever I'm crying and pooping respectively, but I don't have objective evidence to prove that - just a theory topped with an attempt at some rather dry humor.
Furthermore, the same endogenous opioid is probably responsible (at least in part) for the so called "runner's high" that I experience for 2-3 hours after finishing my morning cardiovascular exercise.
Interesting article by the way. It's good to know that crying (emotionally) results in a statistically significant release of endorphins, and that I most likely wasn't experiencing a placebo effect (when crying - not sure about the pooping yet).