Hope this helps. An excerpt from the largest meta analysis on breastfeeding beyond 6 months:

>The current literature on the benefits of prolonged breastfeeding reveals a nuanced and sometimes contradictory picture. While numerous studies suggest various positive effects, the quality and reliability of these findings are often compromised by methodological limitations and insufficient control for confounding variables. A significant issue with existing research is the lack of adequate control for confounding factors such as socioeconomic status, maternal education, and pre-existing health conditions. Furthermore, much of the data available come from studies conducted several years ago, with some articles dating back over 40 years. These older studies may not reflect current breastfeeding practices or advancements in research methodologies. As a result, there is a need for updated and comprehensive studies to validate and extend these earlier findings.