best source I could find for the 'understimulation' claim was this: https://academic.oup.com/ije/article/39/2/370/684049/Bored-to-death https://academic.oup.com

best source I could find for the 'understimulation' claim was this: https://academic.oup.com/ije/article/39/2/370/684049/Bored-to-death https://academic.oup.com/ije/article/39/2/370/684049/Bored-t.... although they attribute boredom as a proxy and not a direct cause of poor health.