As hypothesized , results showed significant Group ( Koru , Wait-List ) Time ( Pre , Post ) interactions for improvements in perceived stress ( F -LSB- @ , @ -RSB- = @ , p = @ , d = @ ) , sleep problems ( F -LSB- @ , @ -RSB- = @ , p = @ , d = @ ) , mindfulness ( F -LSB- @ , @ -RSB- = @ , p < @ , d = @ ) , and self-compassion ( F -LSB- @ , @ -RSB- = @ , p < @ , d = @ ) .