(S (S (CC But) (S (S (BASENP (DT the) (JJ new) (NN meta-analysis)) (VP (VBZ shows) (SBAR (IN that) (S (BASENP (NN melatonin)) (VP (VBZ does) (VP (ADVP (RB indeed)) (VP (VB have) (NP (BASENP (JJ positive) (NNS effects)) (PP (IN on) (BASENP (NN sleep))))))))))) (COLON --) (SBAR (RB even) (SBAR (IN though) (S (NP (BASENP (NN some)) (PP (IN of) (BASENP (DT the) (VBN analyzed) (NNS studies)))) (VP (ADVP (RB also)) (VP (VBD involved) (NP (BASENP (JJ high) (NNS doses)) (PP (IN of) (BASENP (DT the) (NN hormone))))))))))) (PERIOD .))