A lighting arrangement and method for improving sleep in a human body having an unbalanced circadian rhythm by helping to normalize melatonin levels in the body. The method includes providing a lighting arrangement having a radiation source that emits near-infrared (NIR) radiation, preferably in the range 760-1400 nm; and a driver circuit that supplies a first driving current to the radiation source. The driver circuit stores a dosing program configured to accumulate a target session energy density at the user and to automatically suppress emission upon reaching the target. In an embodiment, a lighting arrangement can further comprise an optical system and the driver circuit comprise program memory for storing a dosing program.