In alternative embodiments, provided are methods for: modifying circadian rhythmicity or timing in a mammal, treating psychiatric conditions or symptoms due to alterations in a human circadian regulatory system, treating sleep problems in a mammal, or inducing sleep or activity suppression, or causing an arousal or wakening reaction, comprising administration to a mammal or human a compound or composition capable of modifying a prokineticin 2 (PK2) expression or activity, and/or a PKR2 (PK2 receptor), a vasopressin receptor (VR), and/or a melatonin receptor (MR) expression or activity.