Relevant sources:
https://ifstudies.org/blog/does-having-children-make-people-happier-in-the-long-run

https://www.pewsocialtrends.org/2010/06/25/childlessness-up-among-all-women-down-among-women-with-advanced-degrees/

https://pubmed.ncbi.nlm.nih.gov/12262530/

https://www.sciencedaily.com/releases/2017/03/170301084924.htm

https://blogs.psychcentral.com/see-saw-parenting/2019/01/child-free-women-the-research/

https://pubmed.ncbi.nlm.nih.gov/12262530/

https://whynokids.com/advice-tips/breeder-bingo/

https://www.independent.co.uk/life-style/many-parents-will-say-kids-made-them-happier-they-re-probably-lying-a7124851.html

https://medium.com/invisible-illness/parenting-and-lying-about-it-eda0bfe67fc3

https://link.springer.com/article/10.1007/s13524-015-0413-2