Nyquil is a nighttime cold medicine. If there is one thing that Nyquil is good for, it is knocking you out so that you can get a good night's sleep. I often have issues falling asleep, so I take a dosage of Nyquil and that puts me to bed perfectly. I've tried other sleep aids, but none of them work, and my doctor refuses to prescribe anything to me. I can fall asleep without Nyquil, but it can take hours before I do. I take Nyquil every night now. Have I grown dependent? I don't believe I have, but I would like other opinions. What are the effects of taking this cold medicine when you don't really need it?