Wrt meditation, the meditation we practice in the west is not properly informed by the teachings of the Buddha. Step #10 of the Buddha's instructions on mindfulness of breathing meditation is "Gladden the mind." The idea is to saturate the mind with joy and satisfaction. Happiness is the proximate cause of concentration, to quote Bhikkhu Buddhadasa, not pure and sustained effort. This is basic jhanna practice in the Theravadan/Thai Forest tradition.
Whenever we talk about meditation broadly like this, I wish we could specify whether it's anapanasati meditation (mindfulness of breathing) or just the dry practice those of us know in the west as vipassana.
Here's the conclusion to a very limited article exploring this area:
"How these meditators achieve periods of extreme joy without common negative side effects could contribute to the scientific “pursuit of happiness” and could pave the way for novel paradigms for rehabilitation and recovery from nervous system injury." From: "Case Study of Ecstatic Meditation: fMRI and EEG Evidence of Self-Stimulating a Reward System" in journal Neural Plast.